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c:\clrc\dabdm.pm3-p.1

 

THE INVERTEBRATES OF A GREAT LAKES COASTAL MARSH

BY

Valerie J. Brady

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Zoology

1992

ABSTRACT
THE INVERTEBRATES OF A GREAT LAKES COASTAL MARSH
BY

Valerie J. Brady

The community structure of the invertebrates inhabiting
an emergent coastal marsh in Saginaw Bay, Lake Huron, near
Quanicassee, Michigan, was determined from vegetation,
sediment, and aquatic dip net collected samples during 1989
and 1990. Fifty-four species of insects were collected in
the vegetation community, while 16 species were found in the
sediment. The macroinvertebrate community was numerically
dominated by Chironomidae, Caenis (Ephemeroptera: Caenidae),
and Oligochaeta. Vegetation-associated macroinvertebrates
reached 50,000 individuals m‘2 and 1.5 gm"2 on December 13,
1990. Sediment macroinvertebrates reached 48,900'm"2 on
July 13, 1990, and the community had a biomass of 2.3 gm—2
on July 13, 1989. Twenty-nine species of Cladocera were
present in the vegetation, and 22 species in the marsh
sediment. Cladoceran abundance was generally dominated by
Chydorus sphaericus (0.F. Muller), while Sida crystallina
(0.F. Muller) dominated the biomass in the vegetation
community. Ostracoda dominated the sediment zooplankton
community. Vegetation zooplankton reached 250,000
individuals'm'3 and 15.1 g'm‘3, while sediment zooplankton

reached 356,700-m‘3 and 5 g m‘3.

ACKNOWLEDGMENTS

I would like to thank my advisor, Dr. Thomas M. Burton,
for suggesting the study of Saginaw Bay emergent wetlands,
and for providing guidance during the many revisions of this
study. I would also like to thank the members of my
committee, Dr. Donald J. Hall, and Dr. Richard W. Merritt,
for all their help throughout this study.

I thank Dr. William L. Hilsenhoff of the Department of
Entomology at the University of Wisconsin-Madison, Mr. Arwin
Provonsha, Department of Entomology, Purdue University, and
Dr. Richard Snider of the Department of Zoology at Michigan
State University, who all helped with identification of the
invertebrates.

Special thanks go to Meg Landis and Steve Ennis for
their assistance with the sorting of the samples and the
field work, respectively. Without their help, this study
could not have been completed. Dana Clover, Tony Alvaro,
Deborah Repert, Dr. Dennis Mullen, and Susan Eggert all
provided assistance with various aspects of this study.

This material is based upon work supported under a
National Science Foundation Graduate Fellowship. Other
support was provided by the Department of Zoology, Michigan

State University.

m

TABLE OF CONTENTS

Page

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . v
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . vii
INTRODUCTION . . . . . . . . . . . . . . . . . . . 1
Background . . . . . . . . . . . 1
Objectives . 3
STUDY AREA . . . . . . . 4
Location . . . . . . . . . 4
Water Depth . . . . . 6
Vegetation and Sediment 7
MATERIALS AND METHODS . . . . 8
Invertebrate Sampling 8
Sampling Design . . . . . . . . . 8
Vegetation Samples . . . . . . . . . . . . . . 9
Sediment Samples . . . . . . . . . . . . . . 13
Aquatic Dip Net Samples . . . . . . . . . . . . 14
Identification . . . . . . . . . . . . . . . . 15
Biomass Calculation . . . . . . . . . . . . 16
Depth-Abundance Relationships . . . . . . . . . 19
Characterization of Site . . . . . . . . . . . . . 19
RESULTS . . . . . . . . 21
Vegetation Invertebrate Community Composition . . 21
Macroinvertebrates . . . . . . . . . . . . . . 21
Insects . . . . . . . . . . . . . . . . 33
Crustacean Zooplankton . . . . . . . . . . 52
Sediment Invertebrate Community Composition. . . . 65
Macroinvertebrates . . . . . . . . . . . . . . 65
Insects . . . . . . . . . . . . . . . . 75
Crustacean Zooplankton . . . . . . . . . . . . 85
DISCUSSION . . . . . . . . . . 95
Great Lakes Coastal Wetland Habitat . . . . . . . 95
Macroinvertebrate Community . . . . . . . . . . . 97
Crustacean Zooplankton . . . . . . . . . . . . . . 111
SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 118
APPENDIX . . . . . . . . . . . . . . . . . . . . . . . 122
LITERATURE CITED . . . . . . . . . . . . . . . . . . . 126

LIST OF TABLES

Regression formula and regression constants used to
calculate insect biomass (Smock 1980) . . . . . . . . 17

Dry weights and regression constants used to estimate
the biomass of the crustacean zooplankton . . . . . . 18

The macroinvertebrate taxa (excluding insects) in the
vegetation of a Saginaw Bay, Lake Huron, coastal

marsh: Percent occurrence, maximum mean number per

m2, and maximum mean dry weight (mg/m2) for selected
taxa . . . . . . . . . . . . . . . . . . . . . . . . 22

The insect taxa in the vegetation of a Saginaw Bay,

Lake Huron, coastal marsh: Percent occurrence,

maximum mean number per m2, and maximum mean dry

weight (mg/m2) for selected taxa . . . . . . . . . . 35

Crustacean zooplankton in the vegetation community of

a Saginaw Bay, Lake Huron, coastal marsh: Percent
occurrence, maximum mean number per m3, and maximum

mean dry weight (mg/m3) for selected taxa . . . . . . 56

The macroinvertebrate taxa (excluding insects) in the
sediment of a Saginaw Bay, Lake Huron, coastal marsh:
Percent occurrence, maximum mean number per m2, and
maximum mean dry weight (mg/m2) for selected taxa . . 67

The insect taxa in the sediment of a Saginaw Bay,

Lake Huron, coastal marsh: Percent occurrence,

maximum mean number per m2, and maximum mean dry

weight (mg/m2) for selected taxa . . . . . . . . . . 76

The crustacean zooplankton in the sediment of a

Saginaw Bay, Lake Huron, coastal marsh: Percent
occurrence, maximum mean number per m3, and maximum

mean dry weight (mg/m3) for selected taxa . . . . . . 88

Comparison of the abundances of selected zooplankton
collected in this study, with their abundance in

other wetlands, as reported in the literature.

Includes notes on species' status in Lake Huron, if
known . . . . . . . . . . . . . . . . . . . . . . . . 113

LIST OF TABLES - Continued

Operational taxonomic unit and identification for
invertebrates collected from a Saginaw Bay coastal
marsh near Quanicassee, Michigan . . . . . . . . . 122

Chironomidae present in vegetation and sediment
on June 30 (preliminary sampling) and July 13,
1989, in a Saginaw Bay, Lake Huron, coastal marsh . 124

Water quality of a Saginaw Bay, Lake Huron, coastal
marsh, near Quanicassee, Michigan . . . . . . . . . 125

W

10

11

LIST OF FIGURES

Location of transects at the Quanicassee coastal
marsh study site on Saginaw Bay, Lake Huron, near
Quanicassee, Michigan . . . . . . . . . . . . . . .

Gerking-Mittelbach sampler for quantitative sampling
of invertebrates associated with aquatic vegetation

Composition of the vegetation macroinvertebrate
community of a Saginaw Bay coastal marsh, based on
abundance . . . . . . . . . . . . . . . . . . . . .

Composition of the vegetation macroinvertebrate
community of a Saginaw Bay coastal marsh, based on
dry weight . . . . . . . . . . . . . . . . .

A. Abundance trends, and B. mean weight of the
macroinvertebrates and insects in the vegetation
community of a Saginaw Bay emergent marsh. In both
graphs, the macroinvertebrate series includes the
insects . . . . . . . . . . . . . . . . . . . . . .

Abundance trends of A. Oligochaeta (Annelida) and
Nematoda, and B. aquatic mites in the vegetation

community of a Saginaw Bay, Lake Huron, coastal marsh

near Quanicassee, Michigan . . . . . . . . . .

Composition of the Oligochaeta community in the
vegetation of a Saginaw Bay, coastal marsh, based on
abundance and dry weight . . .

Abundance trends of selected Gastropoda in the
vegetation community of a Saginaw Bay coastal marsh

Composition of the vegetation insect community of a
Saginaw Bay coastal marsh, based on abundance .

Composition of the vegetation insect community of a
Saginaw Bay coastal marsh, based on dry weight

Abundance trends of the Diptera, A. Chironomidae,

and B. Ceratopogonidae, in the vegetation community
of a Saginaw Bay, Lake Huron, coastal marsh

vfi

ll

24

25

27

28

3O

32

39

41

42

LIST OF FIGURES - Continued

12

l3

14

15

16

17

l8

19

20

21

22

Composition of the Chironomidae community in the
vegetation of a Saginaw Bay coastal marsh, based on
abundance and dry weight . . . . . . . . . .

Abundance trends, including standard error, of
Ishnura verticalis Say (Odonata: Coenagrionidae) in
a Saginaw Bay coastal marsh . . . . . . . . . . .

Relationship between abundance and A. water depth,
or B. distance from shore for Ishnura verticalis
Say (Odonata: Coenagrionidae) in the vegetation
community of a coastal marsh, Saginaw Bay, Lake
Huron . . . . . . . . . . . . . . . . . . . . . .

A. Abundance trends of Caenis nymphs, and B.
relationship between water depth and Caenis
abundance, in the vegetation community of a Saginaw
Bay, Lake Huron, coastal marsh near Quanicassee,
Michigan . . . . . . . . . . . . . . . . . . . . .

Abundance trends of selected Trichoptera species in
the vegetation community of a Saginaw Bay coastal
marsh. A. Selected Hydroptilidae. B. Selected
Leptoceridae . . . . . . . . . . . . . . . . . . .

Abundance trends of crustacean zooplankton
associated with the vegetation of a Saginaw Bay
coastal marsh . . . . . . . . . . . . . . . .

Mean dry weight of crustacean zooplankton associated
with the vegetation of a Saginaw Bay coastal marsh

Abundance trends of selected Cladocera in the
vegetation community of a Saginaw Bay coastal marsh

Mean dry weight of selected Cladocera in the
vegetation community of a Saginaw Bay coastal marsh

Relationship between abundance and A. water depth,
or B. distance from shore for Eurycercus lamellatus
(Cladocera: Chydoridae) in the vegetation community
of a Saginaw Bay coastal marsh . . . .

Relationship between abundance and A. water depth,
or B. distance from shore for Sida crystallina
(Cladocera: Sididae) in the vegetation community of
a Saginaw Bay coastal marsh . . . . . . . . .

Wfi

44

46

47

49

51

53

54

6O

61

64

66

LIST OF FIGURES - Continued

23

24

25

26

27

28

29

Composition of the sediment macroinvertebrate
community of a Saginaw Bay coastal marsh, based on
abundance and dry weight . . . . . . . . . .

A. Abundance trends, and B. mean dry weight of
macroinvertebrates and insects in the sediment
community of a Saginaw Bay coastal marsh. In both
graphs, the macroinvertebrate series includes the
insects . . . . . . . . . . . . . . . . . . . . .

Abundance trends of A. Oligochaeta (Annelida) and
Nematoda, and B. aquatic mites in the sediment
community of a Saginaw Bay coastal marsh . . .

Composition of the Oligochaeta community in the
sediment of a Saginaw Bay coastal marsh, based on
abundance and dry weight . . . . . . . . . . .

Composition of the sediment insect community of a
Saginaw Bay coastal marsh, based on abundance and
dry weight . . . . . . . . . . . . . . . . . .

Abundance trends of A. Chironomidae (Diptera), and

B. Caenis latipennis Banks (Ephemeroptera: Caenidae)

in the sediment community of a Saginaw Bay coastal
marsh . . . . . . . . . . . . . . . . . . . . . .

Composition of the Chironomidae community in the
sediment of a Saginaw Bay coastal marsh, based on
abundance and dry weight . . . . . . . . . .

7O

71

73

74

79

80

82

30 Abundance trends of selected insects in the sediment
community of a Saginaw Bay coastal marsh . . . . .

31 Abundance trends of crustacean zooplankton associated
with the sediment of a Saginaw Bay coastal marsh .

32 Mean dry weight of crustacean zooplankton associated
with the sediment of a Saginaw Bay coastal marsh .

33 Abundance trends of selected Cladocera in the
sediment of a Saginaw Bay coastal marsh . . . . . .

34 Mean dry weight of selected Cladocera in the
sediment of a Saginaw Bay coastal marsh . . . . . .

35 A. Average water depths, including highs and lows.
B. Relationship between water depth and distance
from shore for samples taken at both sites in the
Quanicassee coastal marsh . . . . . . . . . . . . .

m

INTRODUCTION

Background

Invertebrates of Great Lakes coastal wetland areas have
received limited attention, especially in recent years.

Most studies of the invertebrate communities were conducted
many years ago (e.g. Judd 1953, Krecker 1939; summary in
Tilton and Schwegler 1978), when pollution and other
environmental conditions in the Great Lakes wetlands may
have been very different than they are at present.

The most abundant zooplankton species in Great Lakes
coastal wetlands are usually quite different from the most
abundant pelagic forms (Krieger and Klarer 1991). This may
also be true for other invertebrate groups. Invertebrates
provide an important source of food to many fish species,
including young piscivores. The Great Lakes contain about
200 species of fish; 90% of these species are directly
dependent on wetlands during some part of their life, while
virtually all Great Lakes fish are indirectly dependent on
wetlands (Whillans 1990). Many of these species feed on the
macroinvertebrates or zooplankton in the wetlands. For
some, such as the yellow perch (Perca flavescens Mitchill),
the amount of macroinvertebrate food available affects their

ability to grow large enough to become piscivores

k)

(e.g. Persson 1987). Thus, knowledge of the invertebrate
community structure is of great potential benefit to fishery
managers.

Invertebrate community structure in coastal marshes may
also provide a sensitive index to pollution inputs, since
many such marshes occur near river mouths where pollution
inputs are great. Several pollution indices rely on
knowledge of invertebrates, for example, the Ohio Index of
Biotic Integrity (Ohio EPA 1988). Before such indices can
be developed, however, one must know what species may have
existed in an area in the past, and what species could
survive in that area if it were unimpacted.

Comparisons of coastal marsh invertebrate communities
based on existing studies are difficult since many different
sampling techniques were used, and only part of the
community was sampled in these earlier studies. Zooplankton
(Krieger and Klarer 1991) and emerging insects (Judd 1953,
McLaughlin and Harris 1990) have been studied, but only
Duffy and Batterson (1987) sampled meio and macro-
invertebrates simultaneously in vegetation, sediment, and

water column habitats of a Great Lakes coastal marsh.

Obiectives
Thus, there is an obvious need for quantitative studies
of coastal marshes in the Great Lakes area, and the main

objective of this study was to provide such data for a

coastal marsh in Saginaw Bay, Michigan. Specific objectives

included

1.

To

column,

the following:

Identify the invertebrates typical of a coastal
emergent marsh community.

Determine the relative abundances of the major
invertebrate taxa in the community.

Determine the seasonal trends of the major
invertebrates in these wetlands.

Compare the invertebrate community structure of
different habitats in the wetland, including
water column, vegetation, and sediment
associated fauna.

accomplish the above objectives, vegetation-water

sediment core-water column, and aquatic dip net

samples were taken during 1989 and 1990 in an emergent marsh

along the southeastern shore of Saginaw Bay, Lake Huron,

near Quanicassee, Michigan.

 

lb

STUDY AREA

Location

The study sites were located in a Scirpus americanus
Pers. marsh along the southeastern shore of Saginaw Bay,
Lake Huron, Michigan. Saginaw Bay is 82 km long and 42 km
wide. The study site was part of a wetland complex that
extends along the southeastern shore of the inner section of
Saginaw Bay from approximately the mouth of the Quanicassee
River (Tuscola County) to the Sand Point/Wildfowl Bay area
(Huron County) of the thumb of Michigan. This is a coastal,
or lacustrine, wetland, with no physical separation between
the wetland and the waters of Saginaw Bay. The emergent
vegetation extends 500 to 750 m offshore in most areas
(Herdendorf et al. 1981).

The study sites were located near the town of
Quanicassee, Tuscola County, Michigan. The 1989 site was
located directly off Bradford Road, while the 1990 site was
located near Vanderbilt Park (Figure 1). The 1989 site was
chosen for its large area of emergent vegetation and its
accessibility. The 1990 site was chosen to be as close as
possible to the 1989 site, but with greater water depth.
These sites were within about one half kilometer of each

other (T. 14 N., R. 7 E., Section 21).

 

 

 

 

 

 

 

 

 

 

 

 

Tuscola County,

 

 

 

 

 

*1:

 

 

 

 

Saginaw Bay

‘1»
d Rd.

’3»
toga?
x
Bradf-

///' Quanicassee

 

P-
II

1989 Transect

M
II

1990 Transect

Scale in Km

 

l 2

 

Figure 1. Location of transects at the Quanicassee coastal marsh study site on
Saginaw Bay, Lake Huron, near Quanicassee, Michigan.

 

 

Wat§;_D§pth

Water depth in the marsh generally increased from
nearshore to offshore areas, but the slope was very gradual.
McNabb and coworkers (pers. comm.) measured an incline of
only 7.6° in this area. The many sandbars created during
seiches and the holes dug by carp (Cyprinus carpio L.) made
the depth progression quite irregular.

Water depth in the marsh varies seasonally and with
changing lake levels. Water levels are typically lowest in
the spring, rise to a peak in July or August with the runoff
from the spring snow melt and rains, and then slowly decline
through the fall and winter to the spring low, following the
typical water level changes of Lake Huron (Busch 1990).
Monthly mean water levels for Saginaw Bay at Essexville,
(approximately 10 km East of the sampling location) varied
from a high of 176.54 m above sea level in October of 1989
(NOAA/NOS 1989), to a low of 176.13 m above sea level in
January of 1990 (NOAA/NOS 1990). Annual water level
fluctuations of 40 to 70 cm have been recorded for Saginaw
Bay marshes (Cole and Weigmann 1983).

Seiches also affect water levels in the marsh. Seiches
of up to one meter have been recorded for Saginaw Bay (Cole
and Weigmann 1983). Seiches are short-term water level
fluctuations caused by strong winds blowing across the bay.
They may last a few hours or a few days. In addition

smaller daily seiches occur due to the shift in wind

direction from onshore during the day to offshore at night

(Batterson et al. 1991).

ygggtation and Sediment

The wetland complex was dominated by the emergent
bulrush, Scirpus americanus Pers., with dense beds of the
cattail, Typgg latifolia L., occasionally interspersed. The
emergent marsh extended out to 600 m from shore in this
area. Submerged and floating-leaved vegetation grew between
the line of lowest water level and the offshore zone of the
marsh, which began between 300 and 400 m from shore

(Batterson et al. 1991). This vegetation included Chara,

Ceratophyllum, Lemna, Najas, Nymphaea, Potamogeton, and

 

Vallisneria (McNabb et al. pers. comm.). Vegetation in the
areas sampled ranged from very dense, 200 to 270 S.
americanus stems per square meter, to nonexistent.

The sediment in this marsh was not the organic mucks
typical of many emergent wetlands. Organic mucks and
detritus did build up in protected areas nearshore, but the
S. americanus marsh substrate was predominantly sand. The
S. americanus growth stabilizes this shifting sand

substrate. Most of the sand grains in the sediment samples

were large enough to be retained in a 250 um sieve.

MATERIALS AND METHODS

Invertebrate Sampling

1. Sampling Design

All samples were collected from a fixed transect using
the point-centered sampling procedure (e.g. Smith 1990).
Each year a transect was laid out through the marsh
perpendicular to the shore, such that depth generally
increased from the nearshore end to the offshore end. The
transect was chosen to intersect typical sections of S.
americanus, submergent macrophytes, and open water areas in
the marsh. T. latifolia islands were avoided since the
vegetation samplers could not be used in them due to the
density of the vegetation. The 1989 transect, located just
off Bradford Road (Figure 1), began approximately 150 m from
shore, and extended 150 m through the marsh along a line of
333°. The 1990 transect was located approximately 0.5 km
south of the 1989 transect, in the vicinity of Vanderbilt
Park (Figure 1). This transect began about 300 m from the
shore, and extended approximately 300 m through the marsh
along a line of 310°.

The transect was relocated in a different area of the
marsh between 1989 and 1990, because low water levels during

the spring of 1990 left the area of the 1989 transect dry.
8

 

Both areas were part of the same large wetland complex, but
the 1990 site was farther from agricultural drainage ditches
than was the 1989 transect. The transect length was also
doubled during 1990 so that sampling points could be shifted
closer to or farther from shore with changing water levels.

Twice a month from July through October of 1989 (except
only once during July), and once a month from April through
December of 1990, five vegetation and five sediment samples
were taken along the transect. Each sample set was taken at
a random distance and direction from a predetermined point
along the transect. The five fixed points were located 20 m
apart along the 1989 transect and 30 m apart along the 1990
transect. For each sample set at each point along the
transect, a random direction (0° to 360° in increments of
10°) and random distance (1 m to 10 m in increments of 1 m)
were obtained from a table of randomly generated numbers.
This determined the exact location where each of the 5 sets
of samples was to be taken. Care was taken never to sample
the same direction twice from any particular fixed point,
nor was any sample taken within one meter of the transect
itself.

2. Vegetation Samples

Epiphytic, nektonic, and epineustic invertebrates were
sampled using a Gerking sampler as modified by Mittelbach
(1981). This Gerking-Mittelbach sampler consisted of a
21.5 cm diameter Plexiglas tube with 224 um nylon netting

attached to one end and sliding Plexiglas doors attached to

10

the other end (Figure 2). The open ring top of a large
mouth, 0.9 l canning jar was clamped to the top end of the
net, allowing large mouth canning jars to be easily attached
and exchanged.

To use the sampler, emergent vegetation in the area to
be sampled was clipped at the water surface. The open
sampler was lowered over the clipped vegetation until it
rested on the sediment. All vegetation inside the sampler
was cut at the sediment surface with a long knife. The
doors of the sampler were closed, the sampler was inverted,
and brought to the surface with the invertebrates and the
vegetation inside. All animals and other small items were
washed from the net into the attached jar, while large
vegetation was removed through the sliding doors and placed
in Ziplock plastic bags. The canning jar was removed,
labeled, and replaced, and the sampler was rinsed between
samples.

Sand frequently jammed the sampler doors so that they
could not be completely closed. The sample was discarded
and retaken if the doors could not be closed tightly enough
to trap the vegetation. Five of these Gerking-Mittelbach
samples were taken on each date, provided the water was deep
enough at each sampling point along the transect
(approximately 5 cm of water were required to operate the
vegetation sampler). Only three Gerking-Mittelbach samples
could be taken on October 27, 1989, and May 10, 1990, due to

shallow water. On April 19, 1990, only three samples were

 

 

 

Height of sampler is one meter.

 

Figure 2. Gerking—Mittelbach sampler for quantitative sampling of
invertebrates associated with aquatic vegetation.

 

12

taken because there was no vegetation present at the other
two sampling locations. Only three Gerking-Mittelbach
samples were taken on December 13, 1990, because an ice flow
was blown into the sampling area just after the third sample
was taken.

At the field laboratory, each sample was washed through
a 250 um sieve, then preserved in 95% ethanol containing
100 mg-l‘1 Rose Bengal dye (Mason and Yevich 1967). All
invertebrates associated with the large pieces of vegetation
were picked the same day and placed in the appropriate
sample. Later, the preserved samples were sorted under 10x
magnification. The Rose Bengal dye stained protein in the
samples a neon pink, speeding and increasing the accuracy of
the picking. Processing time for vegetation samples ranged
from one hour for early spring samples, with an average of
47 invertebrates per sample, to 20 to 30 hours per sample
for fall samples, when up to 3,000 invertebrates were found
in each sample. Vegetation and detritus in these samples
made accurate subsampling impossible, so each vegetation
sample was completely picked.

Invertebrate numbers from each sample were converted to
number'm”2 by the following formula:

Area: 7rr2 = “0.0975 m)2 = 2.98 x 10“2 m2

Zooplankton numbers were converted to number'm‘3 by the
following formula:

Volume: nrzh = n(0.0975 m)2 x (water depth in m)

13

The five vegetation samples collected on each date were
treated as five subsamples of a single sample for each date
to provide means and standard errors.

3. Sediment Samples

Benthic invertebrates were sampled using a corer made
of Plexiglas tube 4.5 cm in diameter and 50.5 cm in length,
capped with a 4.5 cm rubber stopper. Each core included
15 cm of sediment plus the water column above it to a total
depth of about 50 cm. Two cores comprised each sediment
sample. No attempt was made to separate invertebrates in
the water column from those residing in the sediments. One
sediment sample was taken in conjunction with each
vegetation sample, for a total of five sediment samples on
each date.

Sediment samples were washed through a 250 um sieve at
the field laboratory, then preserved in 95% ethanol which
included Rose Bengal dye. Each sediment sample was divided
into sevenths before it was picked, using a subsampling
device similar to that described by Waters (1969). Each
subsample was floated in a sugar solution (300 g sucrose per
1 of water, Anderson 1959) to further speed the picking
process. All floating material was sieved off and sorted
under 10x magnification. Non-floating material was searched
in a white enamel pan using a 10x magnifying lamp. To
insure that an adequate number of organisms were obtained to

characterize the sample, up to three sevenths were picked,

14

until at least 50 organisms were found. Once picking of a
subsample was started, it was sorted completely.

The numbers of invertebrates in each sediment sample
were converted to number-m"2 based on the following formula:
Area: nrz = fl(0.024 m)2 x 2 cores per sample
= 7.24 x 10‘3 m2

Zooplankton numbers were converted to number‘mf3 by the
following formula:
Volume: nrzh = n(0.024 m)2 x (0.15 m + water depth to
0.35 m maximum) x 2 cores per sample

The five sediment samples were also treated as five
subsamples of a single sample for each date.

Sediment samples were processed in this manner through
July 13, 1990. No sediment samples were processed after
this date due to the large amount of time required, and the
low return of information for this work. The first seventh
of each sediment sample required approximately five hours
processing time, with about three hours required for each
subsequent seventh. When completed, only 50 to 100
organisms would have been obtained.

4. Aquatic Dip Net Samples

Aquatic dip net samples were taken, beginning in
September of 1989, to insure that fast-moving invertebrates
were being represented if they escaped the Gerking-
Mittelbach sampler. A single dip net sample of 15 to 20

sweeps through the water was taken from the middle of the

transect from September, 1989, through May, 1990. Beginning

15

in June of 1990, one dip net sample was taken in conjunction
with the other two sample types, for a total of five dip net
samples on each date. Each of these dip net samples
consisted of 10 sweeps of the net through the water; the
sweeps were 1 m apart, with the top of the net kept just
below the surface of the water to standardize the depth.

All dip net samples were live-picked in a white enamel
pan within 24 hours of collection, and preserved in 70%
ethanol. Samples were stored at 4°C until they were picked.

5. Identification

All invertebrates were identified to Operational
Taxonomic Unit (OTU's). The OTU's and the references used
for identification, are shown in Table A-1. Dr. William L.
Hilsenhoff of the Department of Entomology, University of
Wisconsin-Madison, confirmed the identification of the
Trichoptera and the odonate, Ishnura verticalis Say.
Identification of the Ephemeroptera, Caenis amica Hagen and
S. latipenniS Banks, was based on a reference collection
identified by Mr. Arwin V. Provonsha of the Department of
Entomology at Purdue University. Chironomidae larvae were
identified to genus or species group for the June 30, 1989,
(preliminary samples) and July 13, 1989, Gerking-Mittelbach
and sediment samples (Table A-2).

Identification of the Oligochaeta as Stylaria, other
Naididae, and Tubificidae was based on a reference
collection identified by Dr. Richard Snider of the

Department of Zoology, Michigan State University. The

i6

oligochaetes in the sediment samples often broke into
pieces. The larger pieces of Oligochaeta were counted to
provide an estimate of the numbers present. (The very small
pieces (<0.2 mm) were not counted).

The crustacean zooplankton were subsampled for
identification after they had been picked from the samples.
All zooplankton were identified if 50 or less were present
in a sample. If more than 50 zooplankton were present, one-
seventh subsamples were taken. All zooplankton in each
subsample were examined, until at least 50 Cladocera and 50
Copepoda had been identified. Other than those mentioned
above, the identifications were not verified by experts.

6. Biomass Calculation

Biomass of the most abundant macroinvertebrate taxa was

calculated for the following dates:

 

1989 1990
July 13 April 19

August 10 June 8
October 7 August 10
October 6

December 13
Average measurements for each group were obtained by
measuring a subsample from each sample. At least 10
randomly chosen individuals were measured, in mm, using a
calibrated ocular micrometer. Dry weight was then
calculated for an "average" individual of each taxon, and
was multiplied by the number of that group present. For the

insect taxa, with the exception of the Ceratopogonidae,

17

regression constants were available from the literature

(Table 1).

Table 1. Regression formula and regression constants used
to calculate insect biomass (Smock 1980).

Regression formula: W=aLb

W = dry weight in mg
L = Length in mm

a = constant

b = constant

CONSTANTS FOR
MACROINVERTEBRATE REGRESSION FORMULA

 

Chironominae a=0.00510 b=2.32
Orthocladiinae a=0.00510 b=2.32
Tanypodinae a=0.00380 b=2.41
Caenidae a=0.00660 b=2.88
Coenagrionidae a=0.0140 b=2.78
Leptoceridae a=0.00190 b=3.12

The dry weights of all other abundant macroinvertebrate taxa
were calculated by the following formula (after Hynes and

Coleman 1968):

w=nr21(1 cm3/1000 mm3)(1.05 g/cm3)(1000 mg/l g)

W = dry weight in mg
r = radius in mm
1 = length in mm

1.05 g/cm3 = specific gravity
Regression equations were used for some of the
crustacean zooplankton taxa (Table 2). For many species,

however, mean dry weights from the literature were used

18

Table 2. Dry weights and regression constants used to estimate the biomass of the

crustacean zooplankton.

 

DRY WEIGHT (#9) OR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZOOPLANKTON CONSTANTS FOR SOURCE
REGRESSION FORMULA

CLADOCERA
Acroperus harpae Baird 6.00 Hall et al. 1970
Alona quadrangularis (0.F. Muller) 3 =0.087 _ b=2.02 Vuille 1991
Bosmina longirostris (0.F. Muller) 1.80 Hall et al. 1970
Camptocercus rectirostris Schodler 5.00 Hall et al. 1970
Ceriodaphnia l 4.20 Hall et al. 1970 ,
Chydorus sphaericus (0.F. Muller) ' 2.00 Hall et al. 1970
Daphnia 35.00 Hall et al. 1970
Diaphanosoma brachyurum Lieven 7.00 Hall et al. 1970
Eurycercus lamellatus (0.F. Muller) 80.00 Hall et al. 1970
llyocryptus a = 0.0404 b = 2.71 Vuille 1991
Latona setifera (0.F. Muller) l a =0.128 b=2.189 McCauley 1984
Leydigia acanthocercoides Fischer ' 6.00 Hall et al. 1970
Leydigia quadrangularis 6.00 Hall et al. 1970
Macrothrix laticornis Jurine 2.00 Hall et al. 1970
Macrothrix rosea Jurine 2.00 Hall et al. 1970
Pleuroxus procurvus Birge 4.00 Hall et al. 1970
Scapholeberis kingi Sars a =0.0566 b=3.079 McCauley 1984
Sida crystallina (0.F. Muller) i a =0.128 0 =2.189 McCauley 1984
Simocephalus l 50.00 Hall et al. 1970

l
COPEPODA !
Acanthocyclops vernalis Fischer 1 8.60 Hall et al. 1970
Eucyclops agilis Koch i 8.00 Hall et al. 1970
Eurytemora affinis Poppe l a =0.00697 0 =2.154 Culver et al. 1985
Harpactacoida 5.10 Vuille 1991

1 Nalepa and Ouigley
OSTRACODA 1 22.00 1983

 

 

19

(Table 2). This allowed calculation of the crustacean
zooplankton biomass on all sample dates.

7. Depth-Abundance Relationships

The relationship between invertebrate abundance and the
depth or distance from shore at which these vegetation
samples were taken was investigated for several of the most
abundant macroinvertebrate and zooplankton groups.
Abundance of each group was plotted against water depth or
against distance from shore in an xy scatter plot to show

any obvious relationships.

Characterization of Site

Physical, chemical, and nutrient data were collected on
each date to characterize the water within the marsh. These
samples were taken from the offshore end of the transect
during 1989 (300 m from shore), and from the center of the
1990 transect (450 m from shore), areas that appeared
"typical" of the study site.

Water and air temperatures were measured to the nearest
0.5°C using a hand-held mercury thermometer. Water
temperatures were taken just above the sediment surface.
Water samples for pH, alkalinity, and chloride were
collected in polyethylene bottles and placed on ice during
transport back to the field laboratory. The pH and
alkalinity were measured within two hours of the time of
collection, while the chloride sample was frozen upon

arrival at the field laboratory. pH was measured using an

20

Orion Research model 701A Ionalyzer. Alkalinity was
measured by titration with sulfuric acid, as specified in
Standard Methods (APHA 1980).

One 250 ml dissolved oxygen sample, collected with the
other water quality samples, was immediately fixed, and was
analyzed at the field laboratory within two hours of
collection using the Rapid Winkler-Azide modification (APHA
1980). The dissolved oxygen values were then converted to
percent saturation of dissolved oxygen. Chloride was
analyzed with a Technicon® AutoAnalyzer II using the
automated ferricyanide method (U.S.E.P.A. 1979). Means and
standard errors were calculated for all parameters each
year, and for both years together.

Water depth was measured with a meter stick where each
series of samples was taken. Depth was measured to the
nearest 0.5 cm, and estimated when wave action made an exact
reading impossible. The water depths on July 13, 1989, were

estimated from the depths measured on August 10, 1989.

RESULTS

Veggtation Invertebrate Communitv Composition

1. Macroinvertebrates

Non-insectan macroinvertebrates were represented by 11
orders, with 16 identified genera, in the vegetation
community of the Quanicassee marsh (Table 3). Oligochaeta,
aquatic mites, Amphipoda, Gastropoda, Sygrg, and Nematoda
were present in 50% or more of the Gerking-Mittelbach
samples. Only Oligochaeta, Amphipoda, and Gastropoda were
collected by aquatic dip net at least 50% of the time
(Table 3).

The vegetation macroinvertebrate community in the
Quanicassee marsh was dominated, both numerically and by
weight, by aquatic insects, oligochaetes, and snails
(Figures 3 and 4). Macroinvertebrates were generally more
abundant and had greater biomass in 1990 than during 1989
(Figure 5). Macroinvertebrates reached their peak abundance
in the vegetation community at the 1989 site on September
22, with a mean of 12,800 m‘2 (Figure 5A), nearly 75% of
which was aquatic insects (Figure 3). Macroinvertebrate
mean dry weight was greatest on October 7, 1989, with
720 mg'm‘2 (Figure 5B), and again, over 70% of this was

aquatic insects (Figure 4).

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111111 insects

D Amphipoda & lsopoda I Others

8 Tardigrada

% Hydra

Composition of the vegetation macroinvertebrate community of a Saginaw Bay

coastal marsh, based on abundance.

Figure 3.

25

 

D Nematoda
W Gastropoda
E Oligochaeta
[11111 Insects

1:1 Amphipoda
§ Aquatic Mites

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Composition of the vegetation macroinvertebrate community of a Saginaw Bay

based on dry weight.

coastal marsh,

Figure 4.

26

At the 1990 site, macroinvertebrate mean abundance was
very low in April and May, only 1,000-m‘2 and 2,000°m‘2,
respectively (Figure 5A). But the macroinvertebrate
community had reached an average of 30,550 macro-
invertebrates'm'2 by July 13, 1990 (Figure 5A). Fifty
percent were oligochaetes, while 42% were aquatic insects
(Figure 3). Macroinvertebrate abundance generally remained
high the rest of the year. In fact, the highest
macroinvertebrate density was on December 13, 1990, with
nearly 50,000-m-2 (Figure 5A). Although 54% were the tiny
Tardigrada (Figure 3), the macroinvertebrate biomass was
still the highest of the study, with a mean of 1,500 mg-m‘2
(Figure 5B). Again, the greatest percentage of this was
aquatic insect biomass (730 mg1m‘2), with the next largest
portion (580 mg°m'2) represented by the amphipod species,
Gammarus pseudolimmnaeus Bousfield (Figure 4).

The Oligochaeta dominated the macroinvertebrate
community in abundance and biomass during July at the 1989
site, and from May through August at the 1990 site (Figures
3 and 4). Oligochaetes were much more abundant in the
vegetation community during 1990 than in 1989 (Figure 6A).
As with all the macroinvertebrates, oligochaete numbers and
biomass were low in April and May of 1990, but they had
greatly increased by June (Figure 6A). Oligochaeta reached
their maximum mean abundance of 15,400-m‘2 on July 13, 1990

(Figure 6A, Table 3).

27

45,000 .
40,000 - \\=\1///*
35,000
30,000 ~
25,000
20,000 - //~
15,0(30 .
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Sample Date

_ Total _.1 Total Insects — Water Temperature
Macroinvertebrates

1,600 r 1989 1990
1,400 I
1,200
1,000
800
600

400

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200

 

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10///61
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12/13/90

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Sample Date

Figure 5. A. Abundance trends, and 8. Mean weight of the macroinvertebrates and insects
in the vegetation community of a Saginaw Bay emergent marsh. In both graphs,
the macroinvertebrate series includes the insects.

28

 

 

 

 

A.
1989
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1990

 

9/13/90
10/6/90
11/8/90

12/13/90

Figure 6. Abundance trends of A. Oligochaeta (Annelida) and Nematoda,
and B. aquatic mites in the vegetation community of a Saginaw Bay,

Lake Huron, coastal marsh near Quanicassee, Michigan.

29

Most of the oligochaetes associated with the vegetation
were in the family Naididae, with the genus Stylaria making

up a large percentage of the numbers on many dates (Figure

7). Stylaria was the most abundant oligochaete group in
August at both sites (Figure 7). On August 10, 1990, there

was an average of 8,800 Stylaria°m?2,'with a mean biomass of
515 mg°m‘2 dry weight (Table 3). Tubificidae were also
found in association with the vegetation. Tubificidae made
up nearly 50% of the 15,400 oligochaeteS'm"2 in the
vegetation community on June 6, 1990 (Figures 6A and 7).

The oligochaetes, especially the Naididae, were often found
inside the cells of senescent Scirpus americanus Pers., with
the number inside the cells increasing with increasing
decomposition of the vegetation.

Nematoda were also found inside the cells of senescent
bulrush vegetation. Nematodes made up a greater percentage
of the macroinvertebrate community, and were more abundant,
at the 1990 site than at the 1989 site (Figures 3 and 6A).
The Nematoda reached their maximum mean abundance and
biomass on June 8, 1990 (Table 3, Figure 6A).

Aquatic mites were also commonly found in the
vegetation samples. Although they made up a larger
proportion of the macroinvertebrate community during July
and August at the 1989 site (Figures 3 and 4), aquatic mites
reached greater mean abundances at the 1990 site (Figure
6B). There were 1,100 aquatic mites mfizvdth.a mean biomass

of 60 mg-m‘2 on August 10, 1990 (Table 3). Aquatic mite

30

T

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osition of the Oligochaeta community in the vegetation of a Saginaw Bay

based on abundance and dry weight.

coastal marsh,

Comp

Figure 7.

densities in the vegetation community were lower after
August 10, 1990 (Figure 6B).

The Gastropoda were represented in the vegetation
community by six species, with three of these (Ferrissia
parallela Haldeman, Phygg heterostropha Say, and Gyraulus
parvus Say) commonly collected (Table 3). The Gastropoda
were not found, or were present only in low numbers, until
August of each year (Figure 8). Gastropoda were more
abundant during August and September, then declined into the
winter (Figure 8). S. parvus, a planorbid, was often the
most abundant gastropod. E. parallela, one of the limpet-
like Ancylidae, was commonly present along the 1989 site,
but uncommon at the 1990 site (Figure 8). S. heterostropha,
on the other hand, reached greater abundances at the 1990
site (Figure 8).

Although aquatic insects, oligochaetes, and snails
usually dominated the vegetation-associated macro-
invertebrate community, Tardigrada made up 54% of the
December 13, 1990, sample numerically (Figure 3), with a
mean density of 24,800'm'2 (Table 3). However, these
Tardigrada had a calculated mean dry weight of only 21.5
mg'm‘2 (about 1% of the macroinvertebrate biomass, Figure 4)
due to their small size. Tardigrada were present from April
through June, and October through December, of 1990.

The most common amphipod was GammaruS pseudolimmnaegg
Bousfield. S. pseudolimmnaeus first appeared in the

vegetation samples at the 1990 site in June, rose to peak

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mean densities of 750m‘2 in September, then declined in
abundance through the end of sampling in December, 1990.
Hyalella azteca Saussure (Hyalellidae) was present only at
the 1989 site, although the Gammaridae were more abundant at
the 1990 site (Table 3). The isopod Aggllus forbegi
Williams was found only at the 1990 site (Table 3).

flygrg was present in vegetation samples from June
through December, and was sometimes quite abundant. There
were 2,700 flygga'mfz (mean density) in June, the first date
in 1990 that they were collected. Mean density of flyggg was
less than 500°m‘2 during the rest of 1990. The only member
of the Pelecypoda found in the marsh was the invading
Dreissina polymorpha Pallas. One small mussel was found in
an October 6, 1990, vegetation sample (Table 3).

2. Insects

Insects were more abundant in the Quanicassee marsh
vegetation in 1990 than 1989, but the difference was not as
great as was the difference in macroinvertebrate abundance
between 1989 and 1990 (Figure 5A). Aquatic insects reached
their greatest mean abundance during 1989 on September 22,
with 9,500 insects~m‘2 (Figure 5A). Greatest aquatic insect
biomass was on October 7, 1989, with 530 mg-m‘2 (Figure 5B).
Aquatic insect densities were low in the spring of 1990
(Figure 5A), but they did make up the largest proportion of
macroinvertebrates present (Figures 3 and 4). Aquatic
insects were much more abundant by September and October of

1990 (Figure 5A), when they made up over 50% of the numbers

and biomass of the macroinvertebrate community (Figures 3
and 4). Aquatic insects had their maximum mean abundance
and biomass on December 13, 1990, with 15,500 insectsm‘2
(Figure 5A) and 730 mg°m‘2:mean dry weight (Figure SB).

More than 54 species of aquatic insects, representing
28 families, were associated with the vegetation in the
marsh, but only seven groups were found in 50% or more of
the Gerking-Mittelbach samples (Table 4). These groups
included the dipteran families Ceratopogonidae and
Chironomidae, three species of Ephemeroptera, the Odonata,
Ishnura verticalis Say, and two Trichoptera species. The
Chironomidae and two species of Ephemeroptera, Caenis amica
Hagen and Caenis latipennis Banks, were the most abundant
insect taxa present in the vegetation community (Figure 9).
Thirty-three of the 54 species of aquatic insects collected
from the marsh vegetation community were found in aquatic
dip net samples, while the Gerking-Mittelbach sampler
collected 47 of the 54 species (Table 4).

From 14% to 93% of the insect community in the
Quanicassee marsh vegetation was chironomid larvae (Figures
9 and 10). The Chironomidae made up a larger percentage of
the insect community, and were more abundant, at the 1990
site than at the 1989 site (Figures 9 and 11A). At the 1990
site, low spring and early summer densities rapidly
increased to a maximum mean abundance of 12,000
Chironomidaem‘2 on July 13 (Figure 11A). Chironomid

abundance remained high through the end of sampling in

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stal marsh,

ct community of a Saginaw Bay coa

40

December (Figure 11A). Their greatest mean biomass (1,100
mg°m52) was on October 6, 1990. Chironomid larvae were
often found inside the cells of senscent s. americanus, with
densities inside the plants increasing as decomposition
progressed from late summer into winter. On actively
growing s. americanus, chironomid larvae were usually found
on the outside of the stems with the periphyton community.
Some of these larvae were attached to the stems by fixed
cases, while others were free living. Free-living
Chironomidae included the Corvnoneura, Tanypodinae, and some
of the Chironomini and Tanytarsini. Most of the other
Orthocladiinae, and some of the Chironomini and Tanytarsini,
constructed fixed cases.

Nine Chironomini, three Tanytarsini, seven
Orthocladiinae, and three Tanypodinae taxa were identified
from vegetation samples on the two dates on which the
Chironomidae were closely examined (Table A-2). Chironomini
larvae were often a large percentage of the abundance and
biomass of the chironomids collected (Figure 12). Both the
Chironomini and the Tanytarsini reached their maximum mean
abundance (41,400'm'2 and 5,200-m‘2, respectively) and
biomass (1,000-m"2 and 100 m-Z, respectively) on October 6,
1990, when they made up most of the Chironomidae in the
vegetation community (Figure 12).

The free-living Corvnoneura never dominated the
chironomid community. Corvnoneura did reach a maximum mean

abundance of 660 larvae°m‘2 on August 10, 1990 (Table 4).

 

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Sample Date
— Standard Error
B.
300 4 1989 1990 1 3o
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— — 7‘41 \ f1 \\ c1 — — ‘\ -— -— .— \ \ 4
\ \ \ C‘I \ O \\\ \ \ Q \ \ \ O — \
Sample Date
_ Ceratopogonidae — Water Temperature

Figure 11. Abundance trends of the Diptera, A. Chironomidae, and B. Ceratopogonidae,
in the vegetation community of a Saginaw Bay, Lake Huron, coastal marsh.

43

Its greatest mean biomass (l6 mg°m'2)'was on October 7 at
the 1989 site, however (Figure 12). The other
Orthocladiinae also reached their greatest mean abundance
(1,300-m‘2) on August 10, 1990, and had their maximum mean
biomass (50 mg-mfz) on this date (Table 4). The Tanypodinae
reached their greatest abundance at the end of the sampling
period each year. The Tanypodinae had a mean density of
1,700°m‘2 on December 13, 1990, and dominated the
chironomids by weight, with 580 mg"nr2 (Figure 12).

The only other dipteran family commonly present and
abundant in the vegetation was the Ceratopogonidae (Table
4). The Ceratopogonidae generally had abundances of 50 to
200 larvae'm'2 during the summer, fall, and winter (Figure
118). They reached their greatest density in September of
both years (Figure 118), but they never made up a large
percentage of the insect community (Figures 9 and 10). The
Diptera families Ephydridae, Muscidae, and Stratiomyidae
were occasionally collected at the 1989 site, but were never
abundant (Table 4).

The only odonate commonly present in vegetation samples
was the coenagrionid damselfly, Ishnura verticalis Say,
although adult dragonflies were routinely seen flying
through the marsh during the summer months (Table 4). ;.
verticalis reached its maximum abundance in September of
both years, but it was much more abundant at the 1989 site
(Figure 13). During 1989, ;. verticalis abundance increased

to a September 22 peak of 800 nymphsm‘2 (Figure 13). The

 

 

44

 

 

 

 

 

 

 

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dry weight)

Sample Date la = abundance w

I Corynoneura

E Tanytarsini [111] Chironomini

@ Tanypodinae

D Other Orthocladiinae

Composition of the Chironomidae community in the vegetation of a Saginaw Bay

Figure 12.

based on abundance and dry weight.

coastal marsh,

45

large individual biomass of the later instar nymphs allowed
this species to dominate the insect biomass (with

380 mg m-Z, Table 4) on October 7, 1989 (Figure 10). l-
verticalis was much less abundant at the 1990 site, but was
collected in low numbers from August through December
(Figure 13). Four other Coenagrionidae species and two
Anisoptera species were collected in the vegetation
community over the two-year study period, but were uncommon
(Table 4).

The density of ;. verticalis in the marSh reached a
peak at water depths of 25 cm to 45 cm (Figure 14A), and
between 150 m and 300 m from the shore at the 1989 site
(Figure 148). But abundance of ;. verticalis decreased with
increasing distance from shore at the 1990 site (Figure
148).

Four species of Ephemeroptera were collected in the
marsh vegetation community; three species were Caenidae and
one was Baetidae (Table 4). Caenis amica Hagen and Caenis
latipennis Banks were the most abundant Ephemeroptera in the
marsh insect community (Table 4). Neither species was
abundant in samples until September of each year.

Q. latipennis had peak abundances in September of both
years (Figure 15A), and made up 62% of the insect community
on September 22, 1989 (Figure 9). Q. latipennis densities
declined after September to 1,000'm‘2 to 2,000'm‘2 through

the end of sampling each year (Figure 15A). g. amica

900 4

1990

1989

46

141 4 1% 1

14 414 1%“

1

 

1,

800

W

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700

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Sample Date

of Ishnura verticalis Say

including standard error,
Coenagrionidae) in a Saginaw Bay coastal marsh.

Abundance trends,

(Odonata:

Figure 13.

m
E
h
a)
o.
h
a.)
3::
E
3
Z
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C
b
c.)
o.
h
o)
42
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1.200

1,000

800

600

400

200

1,200

1,000

800

600

400

200

47

 

 

T
1 I
1 .
1
i
1 -
1 I
1 I
1 I
' I I
|
T .1 ' .1 '
I
I I
I
.1. I
1 I I I
1 I I
1 I I I I II
1 I I I
1 I I I I I I I I
-——I—-—-—I—I—I—I———I—I—I—-—I-—I—I—I—I+I—I 4 4
0 10 20 30 40 50 60 7O 80
Depth in cm
* 1989 1990
1
- I 1
. .
‘7 I I 1
I
I
- I
.- I I
4— I I
1 I I
1 I
. I I
; I
1 ' .1 .
I I I I
1 I I I I I
1 I l I I
1 g 7‘ I I 1 I I I I
O 100 200 300 400 500 600

Distance from Shore in meters

Figure 14. Relationship between abundance and A. water depth, or B. distance from
shore for Ishnura verticalis Say (Odonata: Coenagrionidae) in the vegetation
community of a coastal marsh, Saginaw Bay, Lake Huron.

48

reached peak abundances of 2,400°m‘2 on October 7, 1989, and
4,200°m‘2 on December 13, 1990 (Figure 15A).

The higher abundances of both Caenis species consisted
largely of early instar nymphs; thus, they rarely made up
much of the insect community biomass (Figure 10). Densities
of Caenis also seemed to be related to water depth (Figure
158). Greater abundances of Caenis were generally collected
from depths less than about 40 cm (Figure 153). However, no
relationship was found between abundance and distance from
shore.

Nymphs of another Ephemeroptera species, Baetis
levitans McDunnough (Baetidae), were consistently collected
in Gerking-Mittelbach samples in low numbers from July
through early October of 1989 (Table 4). Greatest mean
abundance for g. levitans was 150 nymphs-m‘2 on September
22, 1989 (Table 4). 5. levitans was only present in the
August and September samples at the 1990 site, and at low
densities.

The Trichoptera were represented by four species each
in the families Hydroptilidae and Leptoceridae, and by one
species of Phryganeidae, Agrypnia vestita Walker (Table 4).
Most Trichoptera were more abundant at the 1989 site than at
the 1990 site. The exceptions were Hydroptila and an
unknown Oecetis species ("species y"), which were only
occasionally collected from the 1990 site (Table 4, Figure

168). The caddisfly larvae usually reached their highest

49

 

 

A.
1989 1990
6,000 ~
2
cfi l5,000 » f
: / c;
g 4,000 - :
é 3,000 - "E
5 8.
2_ 2,000 - E
_ <2)
8 1——
2 1,000 — E
O
3
0
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§£$_QQQQQQQQQQQQQ
"’7 <3 '2’ w (\l l\ \ 1? O m m 0 ”’3 LC 00 V“,
—— -— :0 \ (\1 \_ rm -— ~— \ — — ——- \ \ —-
\ \ ‘\ :73 \ C \ \\ \ LO \ \ \ O — \
Sample Dates
— Caenis latipennis [: Caenis amica — Water Temperature
B.
20,000 T
18,000 11 I
1 I
16,000 +
14,000 +
N 1
E 12,000 4 .
a. :
._ 10,000 T
<2 1
_:>
E 8,000 r I
Z: I
6,000 + ' .
‘ I
4,000 + I I I I
1 I
2.000 T '_ " .' .I. ' .1 .1 -
1 H - I ‘ '
o ;__-_'I_u—l____—-—-—I—u'—H——3_I_l—-;_u__1
O 10 20 30 4O 50 60 7O 80
Depth in cm

Figure 15. A. Abundance trends of Caenis nymphs, and B. Relationship between water
depth and Caenis abundance, in the vegetation community of a Saginaw Bay,
Lake Huron, coastal marsh near Quanicassee, Michigan.

50
densities in the vegetation community in September,
especially during 1989 (Figure 16).

The Hydroptilidae, Agraylea multipunctata Curtis, and
another unidentified Oecetis species ("species x") were the
most abundant, and the most common, Trichoptera species at
both sites. Both species reached mean abundances of 200 to
250 larvae-m‘2 during September of 1989 (Table 4, Figure
16). Oecetis species x was slightly more abundant in
December than in September during 1990, however (Figure
16B).

Aquatic Coleoptera were present in vegetation samples
only occasionally, and in very low numbers. Six genera,
representing four families, were collected, with four of
these genera only found at the 1989 site; two of these four,
Dubiraphia and Phloeonomus, were collected only once (Table
4). Adult Gyrinidae eluded capture even by the dip net,
although they were often observed in small groups in the
marsh. Two Gyrinus larvae were captured in Gerking-
Mittelbach samples in 1989 (Table 4).

Five of the nine Hemiptera species found were collected
only from the 1990 site (Table 4). Four of these species,
including the only Notonectidae and Veliidae found, were
only collected in dip net samples (Table 4). Trichocorixa
pales Kirkaldy was the most abundant hemipteran in the
vegetation community (Table 4). T. pales was present from
mid-July through September of both years, reaching a mean

abundance of 640 adults and larvae-m‘2 on August 10, 1990

200
180
E 160
__ 140
C)
3 120
Q)
g 100
2‘ 80
g 60
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20
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1990 7 30
l
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"— '_ (\J \ C\‘ \ N -— v— \ v— -— -— \ \ —
\ \ \\ ’31 \\‘ - Q \\ \\ \ LO \ \ \\ O '_ \
1'\ (I) CC) 7" *- O 'T m f\ m (3" "— '— N

Sample Date

Agraylea — Orthotrichia 1:: Oxyethira __ Water

 

 

multipunctata Temperature
1989 1990
250 T 1 7 30
1 1
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CV ~ ‘\-, i ‘ _ 25 ’-
: 200 T /\ \ ':
h l \V/ \\ — i , \ Q)
<3 1 E , /’ - 20 5
C:- = 1 ‘2:
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o E 1) .E
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E 1 15 E T;
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"\ \\‘ \ \\ \,\ \\ \\ \‘ \ \ \ \ \ \ \
m CD <T 30 -."\J .\ 573 C ”.‘C “A \‘J ”'3 to CO V“.
.— .— 1". J \ [\J "\ \ f 1 .— .— \ \ ,— .,_ _. \‘ \ v—
\‘ x. " ‘x \. ’3‘. \x. 3 \‘x. “\- _ \\ 'Q \\. “ ~-~.. \ :2 -— \\
\ CO CO 1‘“ —— '3 m '\ CT: ’30 — — :‘~J
Sample Date
L__#- Oecetis E Oecetis _ Oecetis —— Water
cinerascens species x species y Temperature

Figure 16. Abundance trends of selected Trichoptera species in the vegetation community

of a Saginaw Bay coastal marsh. A. Selected Hydroptilidae. B. Selected
Leptoceridae.

52

 

(Table 4). Adult 1. naias and Mesovelia mulsanti White were
not collected until at least August (1990 site) or early
September (1989 site).

3. Crustacean Zooplankton

Crustacean zooplankton community abundance in the
vegetation was low in July and August of 1989 (Figure 17).
The biomass peak for 1989, however, occurred on July 13, the
first date sampled, with 9,300 mg-m"3 (Figure 18). While
zooplankton biomass generally declined after July 13 (Figure
18), abundance did not peak until October 27, 1989, with
243,600 zooplanktorS'm'3 (Figure 17). Numbers and biomass
were low for the vegetation zooplankton community during
April of 1990 (Figure 17 and 18), with only 4,600'm‘3 and
86 mg'm'3, respectively. Zooplankton abundance and biomass
increased to a small June peak, and then rose to a larger
peak on August 10, 1990, with 220,000°m‘3 and 15,100 mg-m-3
(Figures 17 and 18). From this peak, density and biomass
declined through the rest of 1990.

The Cladocera were generally the most abundant
zooplankton in the vegetation samples. Twenty-nine
Cladoceran species from five families were collected, with
the family Chydoridae being the best represented (Table 5).
The Chydoridae dominated the zooplankton community abundance
during September and October of 1989, with 66% of the total
mean abundance (Figure 17). They also made up about half of
the zooplankton community biomass from September 22 through

the end of the 1989 sampling on October 27 (Figure 18).

////
\\\\\e‘///

53

 

 

 

250,000

200,000

ISO 000
100,000 »

{111 13d JequmN 009w

50,000

06/21/31
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Sample Date

L1 Other Cladocera § Cyclopoida

llllfl Sididae

E Daphniidae

% Chydoridae

I Ostracoda

W Harpacticoida

% Calanoida

Abundance trends of crustacean zooplankton associated with the vegetation of a

Saginaw Bay coastal marsh.

Figure 17.

54

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55

However, during July and August of both years, the two
large Sididae species, gig; crystallina (0.F. Muller) and
Latona setifera (0.F. Muller), dominated the biomass of the
crustacean zooplankton community (Figure 18), despite never
representing more than 37% of the zooplankton numbers
(Figure 17). This was especially apparent on August 10,
1990: Sididae mean biomass reached 12,000 mg°m'3 (Table 5),
representing 79% of the zooplankton community biomass
(Figure 18).

Cyclopoida was the most abundant copepod family in the
vegetation community. Two species, tentatively identified
as Acanthocyclops vernalis Fischer and Eucyclops agilis
Koch, were collected in the marsh (Table 5). Cyclopoida
were abundant during September and October of 1989, and May,
June, and August of 1990 (Figure 17). The Cyclopoida
reached their greatest abundance of 60,100 copepodS°nr3 on
October 7, 1989 (Figure 17), with a biomass of 500 mg°m‘3
(Figure 18). The Cyclopoida made up 69% of the zooplankton
community abundance (Figure 17) and 64% of the zooplankton
biomass on May 10, 1990 (Figure 18). The cyclopoid
population declined through July, 1990, then rose to its
1990 maximum of 48,000 copepodS'm‘3, 400 mg'm‘3, in August
(Figures 17 and 18). The Cyclopoida declined through the
fall of 1990, but exhibited a small peak in December
(Figures 17 and 18).

Only one species of calanoid copepod, tentatively

identified as Eurytemora affinis Poppe, was a common part of

56

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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58

the vegetation zooplankton community (Table 5). E. affinis
had abundance peaks at the end of August, and again in early
October at the 1989 site, but was generally more abundant at
the 1990 site. In 1990, g. affinis exhibited a small spring
peak and then a much larger peak in August, with a mean
abundance of 11,000-m‘3 (65 mg-m'3).

Harpactacoida density in the vegetation community was
very low until October of 1989 (Figure 17); on October 27,
harpactacoid copepods reached a mean abundance of 6,200-m‘3,
with a mean dry weight of 30 mg-m‘3. Like the other copepod
groups, the Harpactacoida exhibited spring, summer, and fall
peaks at the 1990 site (Figure 17). The harpactacoid
copepods reached their greatest abundance on November 8,
1990, with a mean density of 8,800°m'3 (45 mg-m'3). They
were nearly equal to the cyclopoid copepods in abundance on
this date (Figure 17).

Ostracoda abundance and biomass in the vegetation were
low until October 27, 1989, when there were 19,200
ostracodS’m‘3, with a mean biomass of 422 mg'm‘3 (Figures 17
and 18). The Ostracoda were more abundant, and made up a
larger percentage of the zooplankton community, at the 1990
site, however (Figures 17 and 18). Ostracoda made up 77% of
the zooplankton abundance (Figure 17), and 91% of the
biomass (Figure 18), in the April 19, 1990, Gerking-
Mittelbach sample due to the very low numbers of Cladocera
and Copepoda. The Ostracoda were also at their lowest

density for 1990. Ostracoda increased to a June peak, and

59

then reached even greater abundances on August 10 and
October 6, 1990, with 37,100°m‘3 and 36,800'm‘3,
respectively (Figure 17). Greatest biomass for the
Ostracoda in the vegetation community was on August 10,
1990, with 1,370 mg'm‘3 (Table 5).

The Cladocera collected in the vegetation community
represented two species of Bosminidae, fourteen species of
Chydoridae, eight species of Daphniidae, three species of
Macrothricidae, and two species of Sididae (Table 5). Of
these, seven Chydoridae, one Macrothricidae, and one Sididae
species were present in 50% or more of the Gerking-
Mittelbach samples (Table 5).

Overall, most of these 29 species of Cladocera were
uncommon, with only a few species dominating Cladoceran
abundance and biomass. Chvdorus sphaericus (0.F. Muller)
reached the greatest densities of any Cladoceran in the
vegetation community, and dominated Cladocera abundance on
October 27, 1989, and June 8, November 8, and December 13 of
1990 (Figure 19). Acroperus harpae Baird made up most of
the rest of the October 27, 1989, abundance peak (Figure
19). Sida crystallina (0.F. Muller) dominated Cladocera
biomass on several dates when it was abundant: July 13,
August 10, and August 24 of 1989, and July 13 and August 10
of 1990 (Figure 20). Either Eurycercus lamellatus (0.F.
Muller) or Along quadrangularis Sars dominated the

Cladoceran biomass during October of 1989, while

60

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62

Simocephalus had the greatest biomass on September 13, 1990
(Figure 20).

Two species of Chydoridae, Alona rectangula Sars and

 

Dunhevedia crassa King, were present only at the 1989 site.
Three other Chydoridae, Chvdorus qibbus Lilljeborg,
Qisparalona acutirostris Birge, and Monospilus dispar Sars,
were present only at the 1990 site (Table 5). However, 9.
sphaericus was commonly collected, and reached the highest
densities of any of the Cladocera. Q. sphaericus reached a
mean abundance of 107,200-m.‘3 on October 27, 1989 (Figure
19), but had a mean dry weight of only 210 mg°m53 due to its
small size. Another chydorid, A. harpae, was the most
abundant Cladoceran on September 8, 1989, with a mean
density of 59,200 individualS'm'3 (Figure 19). This species
also had a small mean biomass of only 355 mg'm‘3 (Table 5).
A. harpae was only abundant in samples during September and
October of each year (Figure 19).

The Chydoridae Camptocercus rectirostris Schodler was
collected on all 1989 sampling dates, and reached its peak
abundance on September 8 with a mean density of 7,800°m‘3
(Figure 19). Q. rectirostris was only collected from
September through November of 1990. This species had a mean
abundance of 25,900'm53 on September 13, 1990, but had
declined to 370-mf3 by October 6 (Figure 19). A.
quadrangularis was collected in Gerking-Mittelbach samples
on every date except August 10, 1989. The greatest

abundances for this species were on October 27, 1989, with

63

16,100'm‘3, and on August 10, 1990, with 17,9oo-m-3 (Figure
19). A. guadrangularis had calculated mean dry weights of
640 mg'm'3 and 730 mg°mf3, respectively, on these dates
(Figure 20).

S. lamellatus, one of the largest Chydoridae, was
collected in all 1989 vegetation samples. This species had
its greatest abundance on September 8, 1989, with a mean of
14,400 individualS'm‘3 (Figure 19), and a mean dry weight of
1,150 mg'm‘3 (30% of the Cladoceran biomass, Figure 20).
Larger individuals of S. lamellatus were sometimes found in
dip net samples (mesh size was 1 mm). S. lamellatus reached
its greatest abundances in water depths of 25 to 45 cm
(Figure 21A). The abundance of S. lamellatus increased with
increasing distance from shore to about 300 to 400 m, and
then declined (Figure 218). S. lamellatus was also more
abundant at the 1989 site than at the 1990 site (Figure
21B).

S. crystallina dominated the Cladoceran biomass,
however, on the dates on which it was abundant (Figure 20).
This Sididae was only present through early October each
year, and was not found in 1990 Gerking-Mittelbach samples
until June (Figure 19). S. crystallina was usually the
largest zooplanktor in the vegetation community, and was
often collected with the dip net. S. crystallina reached
abundances of 7,600'm'3 in June, 1989, and 30,700'm'3 on
August 10, 1990 (Figure 19). S. crystallina had a mean

biomass of 8,850 mg-m‘3 and 11,400 mg°m‘3 on these two

64

45,000
40,000
35,000
30,000
25,000

20,000

Number per m5

15,000
10,000

5,000

 

--. - —+—- _,+_ —— —r—- —+——+——+ —-+-—-r
I
I
I

O
30 4O 50 60

Depth in cm

0
O
N
O

1989 1990
45,000 T I

40,000 «i-

35,000

 

1
30,000 4-

i

I

- r
25,000 '+ .
20,000 i

Number per m5

15,000

___+. -_*_ __

‘i
I
II

10,000 I
5,000 i
r : |. I I : i I I ' 4_I
0 r . H : I——r
o 100 200 300 400 500 600

Distance from Shore in meters

—r

I

-
I

 

 

 

Figure 21. Relationship between abundance and A. water depth, or 8. distance from
shore for Eurycercus lamellatus (Cladocera: Chydoridae) in the vegetation
community of a Saginaw Bay coastal marsh.

65

dates, respectively, dominating the entire vegetation
zooplankton community biomass (Figures 17 and 19).
S. crystallina, like S. lamellatus, showed evidence of

a relationship between abundance and water depth/distance

from shore (Figure 22). S. crystallina was more abundant at
depths greater than 30 cm (Figure 22A). This species was

most abundant in the samples taken farthest from the shore
at the 1989 site, but no such relationship was evident at

the 1990 site (Figure 228).

Sediment Invertebrate Communitv Composition

1. Macroinvertebrates

Nine orders of non-insectan macroinvertebrates were
present in the sediment of the Quanicassee marsh (Table 6).
Three of these, Oligochaeta, aquatic mites, and Nematoda,
were present in 50% or more of the sediment core samples
(Table 6). The sediment macroinvertebrate community was
dominated by aquatic insects, oligochaetes, and nematodes
(Figure 23). Aquatic insects made up a large percentage of
the abundanceand biomass at the 1989 site, while nematodes
were a large percentage of the sediment macroinvertebrate
community abundance at the 1990 site (Figure 23). It was
the Oligochaeta, however, which most often dominated the
biomass of the sediment macroinvertebrate community (Figure
23).

Although the macroinvertebrate community in the

sediments did not reach its 1989 maximum abundance until

66

100,000 T
90,000 1
80,000 +
70,000 «—
60,000 4-
50,000 ~~ '
40,000 +

Number per m3

30.000 ‘0
20,000 4* I
10,000 4* I .-
o h—W‘ = : ; A.

 

 

 

Depth in cm

1989 1990
100,000 -r

90,000
80,000
70,000
60,000 ; i
50,000
40,000
30,000
20,000

-{___ _

 

{ _

Number per mi

1

1 u

r - -
1

——+——+—~+— +—+
I

10,000

 

4--

 

I—J—l—l—l—I I l—I—l———-I-—l

100 200 300 400 500 600

O

0

Distance from Shore in meters

Figure 22. Relationship between abundance and A. water depth, or B. distance from
shore for Sida crystallina (Cladocera: Sididae) in the vegetation community
of a Saginaw Bay coastal marsh.

67

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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68

 

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69

October 27 (Figure 24A), the community's greatest biomass
was on July 13, the first date samples were collected, with
2,300 mg°m'2 (Figure 24B). On this date, aquatic insects
made up 87% of the macroinvertebrate biomass (Figure 23).
Macroinvertebrate abundance was about 9,000°m'2 to
10,000'm‘2 during July and August of 1989. The sediment
macroinvertebrate community then increased to a peak
abundance of 28,700'm‘2 on October 27, 1989 (Figure 24A),
75% of which were insects (Figure 23). The biomass,
however, had declined from its July 13 peak to 1,000 mg-m‘2
by October 7 (Figure 248).

The sediment macroinvertebrate community, unlike the
macroinvertebrate community in the vegetation, was
moderately abundant in the spring of 1990, with 6,000
individuals-m."2 on April 19 (Figure 24A). 16,000
macroinvertebrates'mfz‘were present by May 10, and the
macroinvertebrate community reached 48,900-m‘2 on July 13,
1990, the last date sediment samples were processed (Figure
24A). Nematoda made up 50% of the macroinvertebrate
abundance on July 13, 1990 (Figure 23). Aquatic insects
made up a much smaller percentage of the sediment
macroinvertebrate community in 1990 than they did in 1989
(Figure 23).

Oligochaeta was the main component of the sediment
macroinvertebrate community biomass on four of the five
dates for which biomass was calculated, even though they

never made up more than 40% of the macroinvertebrate

70

006/El/L

   

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community of a Saginaw Bay

71

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35,000

30,000 0
25,000

20,000 r
15,000 -

10,000 0
5,000 I —
O . -

1989

Celsius

Mean Number per 1112
Waler lempcralurc 1n

 

8/24/159
9/1/19
9/22/89
10///89
4/19/90
5/10/90
b/8/90
7/13/90

on
30
‘\
1\
(\J
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0

Sample Date

_ Total ____‘ Total Insects —_ Water Temperature
Macroinvertebrates

2,500
1989 1990

T
1
-

2,000

1,500

Mean Weith in ”lg/n1?

 

     

 

7/13/89 8/10/89 10/7/89 4/19/90 6/8/90
Sample Date

I Macroinvertebrates '1: Insects

Figure 24. A. Abundance trends, and 8. mean weight of macroinvertebrates and insects
in the sediment community of a Saginaw Bay coastal marsh. In both graphs,
the macroinvertebrate series includes the insects.

72

community's abundance (Figure 23). Oligochaete abundance in
the sediment was between 2,000°m'2 and «41,000'm"2 on most
dates in 1989 (Figure 25A). Oligochaeta densities were
between 5,000'm“2 and 10,000-m‘2 during 1990. Their
greatest mean abundance and biomass in the sediments was on
June 8, 1990, when there were 10,400°m72,‘with a mean dry
weight of 1,120 mg'm'2 (Table 6, Figure 25A).

Most of the oligochaetes in the sediments were
Tubificidae. The genus Branchiura made up a large
percentage of the oligochaete biomass on August 10
(840 mg'm‘z) and October 7 (505 mg'm‘z) at the 1989 site
(Figure 26). Branchiura reached a peak mean density of
580m"2 on October 7, 1989. The other Tubificidae reached
mean abundances of 9,500'm"2 on June 8, 1990, with a
calculated mean dry weight of 1,100 mg-m"2 (Table 4).

Nematoda were much more abundant in the sediment during
1990 than in 1989 (Figure 25A). They made up nearly 75% of
the macroinvertebrates collected on April 19, 1990 (Figure
23), and reached a maximum mean abundance of 24,200'm'2 on
July 13, 1990, (Figure 25A), with a mean biomass of
15 mg'm‘2 (Table 6). At the 1989 site, Nematoda densities
were low until September 22, and did not get as high as
during 1990 (Figure 25A).

Aquatic mites were commonly collected in the marsh
sediment, although they did not make up a major percentage
of the macroinvertebrate community abundance or biomass

(Table 6). Aquatic mite numbers were low in July and early

   

73

 

 

         

A.
1989 1990
25,000 iv _. 3°
: s
‘N E
E 20,000 8
Q .E
f 15,000 3
Q) 2
‘2 e
‘5 10,000 a
z E
: Q
U l-—
E 5,000 5
S
O
0‘ 3" C73 (35 0‘! 0‘ (3‘ O O O 0
w CD to CO CD CO CO ~35 <75 G) O"
\ \ \ \ \ \ \ \ \ \ \
N1 C) fi' no CV l’\ l\ O" C) w H?
— — N \‘ N \ N .— -— \ .—
\ \ \ O‘I \ O \ \. \ to \
'\ or: w 05 -— (3 V Ln |\
Sample Date
:l Oligochaeta _ Nematoda — Water Temperature
B.
2,500 —
: 1989 1990
2,000 +
CE
5 3 '
Q 1,500 f
a
.D
g
2 1,000 ~
C .
C l
C)
E .
500 + 1
0 z 7 = {7 = la E
(3‘! 30 C33 05 CW C7} C3 C O C)
00 ()0 C1) 30 GO DO 30 Q“ C)" 3‘
\ \ \ \ \ \ \ \ \ \
M C) V w (\J I\ l\ 03 0 NT)
~— — N \ (\r \ ”\A — ~—~ -—
\ \ \ C) \ O \ \ \ \

Sample Date

— Standard Error

Figure 25. Abundance trends of A. Oligochaeta (Annelida) and Nematoda, and B. aquatic
mites in the sediment community of a Saginaw Bay coastal marsh.

74

M06/8/9

 

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Sample Date (a

llIll Other Tubificidae El Others

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I Other Naididae

@ Stylaria

osition of the Oligochaeta community in the sediment of a Saginaw Bay

based on abundance and dry weight.

coastal marsh,

Comp

Figure 26.

 

75

August of 1989. After August 24 aquatic mite mean densities
ranged between 500-mf2 and 1,500-m‘2 (Figure 25B). Mite
abundances were low during 1990, except on June 8. On this
date there were 1,300 mites'm*3(Figure 25B), with a mean
biomass of 50 mg'm‘2 (Table 6). Other, less common and
abundant members of the sediment macroinvertebrate community
included Hirudinae, aggra, Tardigrada, Turbellaria, two
Gastropoda species, and the amphipod Gammarus
pseudolimmnaeus Bousfield (Table 6).

2. Insects

Aquatic insects were an important part of the
Quanicassee marsh sediment macroinvertebrate community
(Figure 24). They made up 77% of the macroinvertebrate
abundance, and 87% of the biomass on July 13, 1989, the
first sampling date (Figures 23 and 24). Aquatic insects
made up over 60% of the community numerically during early
August and throughout October of 1989 (Figure 23).

More than 16 species of aquatic insects were collected
in sediment core samples, representing 12 families (Table
7). However, only three taxa, Chironomidae, Caenis
latipennis Banks, and Ishnura verticalis Say, were present
in 50% or more of the samples (Table 7). Chironomidae
larvae and Caenis (Ephemeroptera) nymphs dominated the
sediment insect community abundance and biomass (Figure 27).

Aquatic insect numbers were low during the summer and
early fall at the 1989 site (Figure 24A). They increased to

their greatest abundance on October 27, 1989, with

76

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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78

19,400 insectsm‘2 (Figure 24A), most of which were
Chironomidae and g. latipennis (Figure 27). Maximum mean
insect biomass in the sediment community was on July 13,
1989, however, with 2,000 mg°m'2 (Figure 248), comprised
almost entirely of Chironomidae (Figure 27). Chironomidae
made up 28% to 100% of the insects collected in the sediment
on all dates (Figure 27). The Chironomidae reached their
greatest densities in 1989 during July and at the end of
October, with over 7,000 larvae-m'2 (Figure 28A). The
Chironomidae made up most of the sediment macroinvertebrate
community abundance and biomass during July (Figure 27).

Chironomidae larvae were the only insects found in the
April 19, 1990, sediment samples (Figure 27). Their numbers
and biomass were low this early in the year, only 1,100-m-2
and 7 mg m'2, respectively (Figure 28A). The density of
Chironomidae in the sediments had greatly increased by July
13, 1990, with 13,300 larvae°m'2 (Figure 28A), when they
again made up most of the sediment insect community (Figure
27) .

Twelve Chironomini, five Tanytarsini, and three
Tanypodinae taxa were identified from sediment samples on
two dates (Table A-2). Orthocladiinae were not generally
present in the sediment samples, with the possible exception
of Cricotopus svlvestris gr. larvae (Table A-2). Larvae
from the tribe Chironomini were the only Chironomidae found
in the two samples from the 1990 site. Chironomini made up

at least 20% of the Chironomidae collected from the

79

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80

 

 

 

A.
20,000 7
18,000 l 1989 1 1990
16,000 5 l (
CV
E 14,000 i l l
5 ‘ l
‘3- 12,000 ‘
E 10 000
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2 8,000
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5 5
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-— -— N \ m \ N — -— \ -—
\ \\ \ 03 \ O \ \ \ LO \
f\ 00 DO 63 —— S) V Ln r\

Sample Data

— Standard Error

Figure 28. Abundance trends of A. Chironomidae (Diptera), and B. Caenis latipennis Banks
(Ephemeroptera: Caenidae) in the sediment community of a Saginaw Bay
coastal marsh.

81

sediments at the 1989 site (Figure 29). Chironomini larvae
had their greatest abundance on July 13, 1989, with a mean
of 3,400-m'2, and with a calculated mean dry weight of

770 mg°m"2 (Table 7) .

Larvae of the tribe Tanytarsini made up the greatest
percentage of the Chironomidae on July 13 and August 10,
1989 (Figure 29). However, Tanytarsini were not present in
the other three sediment samples examined (Figure 29). The
Tanytarsini also reached their peak mean densities in the
sediment on July 13, 1989, with 4,200 larvae°m‘2, and a mean
biomass of 1,000 mg°m‘2 (Table 7). Tanypodinae were the
least abundant chironomid taxa in the sediment samples, but
did comprise 50% of the chironomid biomass on October 7,
1989 (Figure 29). This was not their greatest biomass,
however; on August 10, 1989, the Tanypodinae mean biomass
reached 75 mg'm'2 (Table 7) .

The only other dipteran family collected from the
sediments of the Quanicassee marsh was the Ceratopogonidae
(Table 7). This family made up less than 5% of the insect
community abundance and biomass throughout 1989 (Figure 27).
Ceratopogonidae numbers were very low in the sediment until
September 22, after which they increased to their peak mean
abundance of 600m"2 on October 27, 1989 (Figure 30).
Fourteen percent of the insects collected on May 10, 1990,
were Ceratopogonidae larvae. Ceratopogonidae also comprised
about 15% of the insect biomass on June 8, 1990 (Figure 27).

May 10 and June 8 were the only two dates in 1990 when

 

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83

Ceratopogonidae were collected in the sediment (Figure 30).

Three species of Ephemeroptera, Baetis levitans
McDunnough, Caenis amica Hagen, and Caenis latipennis Banks,
were part of the insect community in the marsh sediment.
The only species commonly collected was Q. latipennis (Table
7). g. latipennis was only abundant in the sediment in the
fall of 1989, but made up at least 50% of the insects
collected during September and October (Figure 27). The two
Caenis species together comprised 60% of the insect biomass
on October 7, 1989 (Figure 27). By October 27, 1989, g.
latipennis reached a mean abundance of 9,700 nymphs-m"2
(Table 7, Figure 28B).

The only Odonata collected in sediment core samples was
the Coenagrionidae, Ishnura verticalis Say (Table 7).
Nymphs of this damselfly species were often collected at the
1989 site, but were not found in the sediment core samples
during 1990 (Table 7, Figure 30). ;. verticalis reached its
greatest mean abundance and biomass on September 22, 1989,
with 400 nymphs-m'2 and 25 mg°m’2, respectively (Figure 30).

Only three species of Trichoptera were found in
sediment samples, and two of them were only found once
(Table 7). The third, an unidentified Oecetis species
("species x"), was fairly abundant on August 24 and October
27 of 1989, with nearly 1,000 larvae-m-2 (Figure 30). The
other insects present in sediment samples were found on only
one date, with the exception of Stenelmis (Elmidae), which

was collected on two dates in 1989 (Table 7).

84

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Abundance trends of selected insects in the sediment community of a Saginaw

Bay coastal marsh.

Figure 30.

85

3. Crustacean Zooplankton

The crustacean zooplankton community abundance and
biomass peaks generally occurred on the same dates in the
Quanicassee marsh sediment and the water column above it
(Figures 31 and 32). The sediment zooplankton gradually
rose to a peak abundance and biomass on October 27, 1989,
with 356,700 zooplanktors mf3 (Figure 31). The zooplankton
had another peak of 239,400-m‘3 on July 13, the last date
the sediment was sampled (Figure 31). Total community
biomass was also greatest on these two dates, with
5,300 mg'm‘3 and 5,000 mg m‘3, respectively (Figure 32).

The sediment crustacean zooplankton community was
dominated by chydorid Cladocera and Ostracoda, although
harpactacoid and cyclopoid Copepoda were occasionally
abundant (Figures 31 and 32). Twenty-two species of
Cladocera, representing five families, were collected in
sediment samples, but most of these were uncommon (Table 8).
Only four species, Alona quadrangularis (0.F. Muller),
Chvdorus sphaericus (0.F. Muller), Eurycercus lamellatus
(0.F. Muller), and Ilvocryptus spinifer Herrick, were
present in more than 20% of the samples (Table 8). No
calanoid copepods were collected, but two species of
Cyclopoida were found. Harpactacoid copepods and ostracods
were present in 80% or more of the sediment samples (Table
8).

Ten of the 22 species of Cladocera collected in

sediment samples were present only in 1989, while six were

 

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collected only in 1990 (Table 8). Five of the 10 species of
Chydoridae were collected only in 1989, while three were
part of the sediment community only in 1990 (Table 8).
Cladocera abundance and biomass were fairly low until
September 22, 1989 (Figure 33).

A. quadrangularis and Q. sphaericus were abundant in
the sediment by October of 1989 (Figure 33). Cladocera
density and biomass in the sediment were often dominated by
only one or two species (Figures 33 and 34). A.
quadrangularis and Q. sphaericus, together, comprised the
October 27, 1989, abundance and biomass peak (Figures 33 and
34). Q. sphaericus had a mean abundance of 83,600'm'3 on
October 27 (Figure 33), but A. guadrangularis made up most
of the Cladoceran biomass with 1,200 mg°m'3 (Figure 34). A.
quadrangularis was even more abundant (36,700°m‘3) and had
slightly greater biomass on July 13, 1990 (Figures 33 and
34). E. lamellatus, a Chydoridae, and Latona setifera (0.F.
Muller), a Sididae, had abundance peaks on September 22,
1989, but were overwhelmed by the larger numbers of the
other species (Figure 33). However, these two species made
up over 50% of the Cladoceran biomass on this date (Figure
34), due to their relatively large size (Table 2).

Very few Cladocera were present in sediment samples in
the spring of 1990, but by July 13 there were 80,000
Cladocera°m‘3 (Figure 33), with a mean biomass as great as
that on October 27, 1989 (Figure 34). The most abundant

species were A. quadrangularis, ;. spinifer Herrick, and

91

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93

Leydigia (Figure 33), with most of the biomass consisting of
A. quadrangularis (Figure 34).

Harpactacoid copepods were collected on all dates
sediment core samples were taken (Table 8). They were
abundant in sediment samples from August 24 through October
27, 1989, and on July 13, 1990 (Figure 31). Harpactacoida
made up 37% of the zooplankton abundance on October 7, 1989
(Figure 31). However, they did not make up a large
percentage of the zooplankton biomass on any date, due to
their small size (Figure 32).

Cyclopoida were less abundant than the Harpactacoida in
the fall of 1989, but were more abundant in the spring and
summer of 1990 (Figure 31). Eucvclops agilis Koch made up
33% of the sediment zooplankton community abundance (with
44,400 individuals-m‘3) and 43% by weight (360 mg'm‘3) on
June 8, 1990 (Figures 31 and 32). This species had its
greatest density on June 8, and was the only cyclopoid
copepod collected in the sediment. The only other
Cyclopoida present in sediment samples was Acanthocyclops
vernalis Fischer. A. vernalis reached its greatest
abundance in the sediment community on October 27, 1989,
with 28,300 m'3.

The Ostracoda most often dominated the sediment
zooplankton community, however (Figures 31 and 32). They
made up over 50% of the sediment zooplankton community
abundance from July through September of 1989, and April,

May, and July of 1990 (Figure 31). The Ostracoda also made

94

up over 50% of the zooplankton biomass on all dates except
June 8, 1990 (Figure 31). The lowest ostracod density in
the sediment during 1989 was 25,200-m‘3 on August 10, 1989
(Figure 31). Ostracoda abundance generally remained between
40,000°m‘3 to 50,000-m‘3 until October 27, 1989. There were
137,300 ostracods-m73 on October 27 (Figure 31), with a mean
biomass of 3,000 mg-m‘3 (Figure 32). Ostracod density was
between 35,000-mf3 and 45,000 nr3 during April, May, and
June of 1990 (Figure 32). There were 129,600 ostracodsm‘3
on July 13, 1990 (Figure 32). Ostracod biomass was about
1,000 mg'm'3 on April 19, 1990, decreased to a low of 253
mg°m‘3 on June 6, then quickly rose to 2,850 mg°m‘3 during
the peak abundance on July 13, 1990 (Figure 32). On October
27, 1989, and July 13, 1990, 57% of the sediment zooplankton

community biomass was Ostracoda (Figure 32).

DISCUSSION

Great Lakes Coastal Wetland Habitat

Duffy and Batterson (1987) described Great Lakes
coastal wetland areas as being an alternately benign and
harsh environment for macroinvertebrates. The water in the
emergent marsh freezes down to or into the sediments during
the winter (Duffy and Batterson 1987). Thus, invertebrate
numbers are very low in the spring, as can be seen in the
Quanicassee marsh during April of 1990 (e.g. Figure 5A).
However, the water in the shallow wetlands heats up faster
than deeper water areas, and gets warmer during the summer.
The warmer water allows the eggs of many species to hatch
earlier, and enables faster growth (Duffy and Batterson
1987). The water temperature in the Quanicassee marsh
generally stayed within 5°C of the air temperature, reaching
26°C in July or August of 1989 and 1990 (Table A-3).
Dissolved oxygen in the Quanicassee marsh was never below
77% saturation, even during the warm summer temperatures
(Table A-3).

The abundant macrophyte growth in Great Lakes coastal
wetlands benefits invertebrates in several ways. Kelley and
fellow researchers (1985) found that nutrients are stored as

emergent macrophyte biomass for only a short period of time

95

96

before they are re-released into the marsh ecosystem.
Decomposition of the macrophyte litter from the previous
year is generally completed by early summer, providing a
pulse of nutrients for the marsh community (Duffy and
Batterson 1987). The macrophytes provide a substrate for
abundant periphyton growth during the summer, greatly
increasing the surface area available for colonization.
Scirpus americanus Pers. shoots in the Quanicassee wetland
provided up to twice as much surface area for periphyton
growth as did the sediments on which the bulrushes grew
(McNabb et al. pers. comm.). In addition, macrophyte
vegetation may provide macroinvertebrates with protection
from fish predation (Hershey 1985).

The emergent vegetation also dampens wave action in the
marsh, providing further physical protection to
invertebrates. McNabb and fellow researchers (pers. comm.)
found that wave height in the Quanicassee marsh was
approximately 30 cm at 500 m from shore, the outer edge of
the emergent marsh. Wave height had decreased to only 5 cm
when it was measured 100 m closer to the shore, due to the
damping effect of the g. americanus (McNabb et al. pers.
comm.). The S. americanus growth, and concomitant decrease
in wave action, helped to stabilize the sandy substrate of
the emergent marsh.

The coastal marsh can be a harsh environment even in
the spring and summer, however. McNabb and fellow

researchers (pers. comm.) measured a water level increase of

97

50 cm in the Quanicassee wetland in just three hours during
a summer storm over Saginaw Bay. The water level decreased
just as rapidly after the storm (McNabb et al. pers. comm.).
Mean depth during my study in the Quanicassee marsh rarely
exceeded 50 cm (Figure 35A). While collecting samples
during a seiche associated with a spring storm on May 10,
1990, I measured water levels which averaged 15 cm lower
than those on April 19, and 30 cm lower than water levels on
June 8 (Figure 35A). This seiche left much of the marsh
with only 3 to 5 cm of water covering the sediments (Figure
35A). Large areas of the stems of emergent macrophytes are
exposed to the air when seiches such as this occur during
the growing season, a potentially lethal situation for all
aquatic life which cannot migrate quickly. In fact, the
periphyton community on g. americanus was well-developed
only on the basal portion of the stems, below the low water
line (Batterson et al. 1991). This decreased the periphyton
distribution to only 46% of the potentially colonizable area
of the stems below the median water level (Batterson et al.

1991).

Macroinvertebrate Community

The macroinvertebrate community in the Quanicassee
emergent marsh vegetation consisted mostly of Chironomidae,
Caenis latipennis Banks and Caenis amica Hagen, Ishnura
verticalis Say, Stylaria and other Naididae, Gyraulus parvus

Say, Physa heterostropha Say, and Nematoda (Tables 3 and 4).

80
70
60
50
40
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Waler Depth in cm

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70

60

50

40

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Wuler Depth in cm

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98

 

 

 

 

 

 

 

 

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Distance from Shore in meters

A. Average water depths, including highs and lows. 8. Relationship

between water depth and distance from shore for samples taken at both sites

in the Quanicassee coastal marsh.

99

Certain Chironomidae, both Caenis species, and the Nematoda
were also a large part of the sediment macroinvertebrate
community (Figures 23 and 27). The only other numerous
group in the sediment community was the oligochaete family
Tubificidae (Figure 26).

The vegetation macroinvertebrate community was much
more diverse than was the macroinvertebrate community in the
sediment. This was especially true for the aquatic insects,
where greater taxonomic resolution was possible (Table 4
versus Table 7). At least 54 species of aquatic insects
were present in the vegetation community (Table 4), while
only 16 were collected for the sediment community (Table 7).
Nearly four times the number of insect species were present
in the vegetation than were collected from the sediment,
even when only 1989 samples are compared (Tables 4 and 7).
The substrate of the s. americanus marsh was predominantly
unstable sand, likely limiting the macroinvertebrate species
able to reside there. Therefore, the sampling scheme for
macroinvertebrates in such an emergent marsh should include
sampling the vegetation in some manner. This habitat would
be especially important during the late summer and fall,
when most of the macroinvertebrates are associated with the
senescent vegetation and detritus.

Sweep samples taken with an aquatic dip net did not
prove adequate for sampling the vegetation macroinvertebrate
community in the Quanicassee marsh. The data in Tables 3

and 4 give the impression that the dip net sampling provided

 

100

a fair indication of the vegetation macroinvertebrate taxa
and their relative abundance. However, sweep net sampling
with the dip net consistently underrepresented the abundance
of most taxa, and completely missed 21 species of aquatic
insects (Table 4), plus 4 other macroinvertebrate species
(Table 3). Many of the taxa that were missed were taxa that
are generally considered macroinvertebrates. On the other
hand, the dip net did capture seven insect species that did
not show up in the more quantitative Gerking-Mittelbach
samples (Table 4).

The sediment invertebrate community should not be
neglected, either. Each sediment-core sample covered only
about half the area of each vegetation sample, perhaps
accounting for part of the difference in the number of taxa
between the two sample types. Macroinvertebrate peak
biomass, however, was greater in the Quanicassee marsh
sediment than in the vegetation (Figures SB and 24B). For
example, macroinvertebrate biomass in the vegetation
community reached a maximum of 1,500 mg-m"2 (Figure SB),
while in the sediment, biomass reached 2,300 mg-m‘2 (Figure
24B). The greatest abundance of macroinvertebrates in the
sediment was also as large as the highest density in the
vegetation, around 50,000'm'2 (Figures 5A and 24A).

One of the most abundant macroinvertebrate groups in
both the vegetation and the sediment was the Oligochaeta.
The difference in the abundance of macroinvertebrates in the

vegetation between 1989 and 1990 (Figure 5A) was largely due

101

to the greater number of oligochaetes present in 1990
(Figure 6A). The Oligochaeta in the Vegetation community
were often dominated by the Naididae (Figure 7). The
Naididae genus Stylaria, found only in the vegetation, was
easily identified at 10x by its distinctive appearance: a
short worm with a pointed "snout" on its anterior end and
large clear "slots" perpendicular to its length on each
segment. Stylaria fossularis was the only oligochaete Duffy
and Batterson (1987) found in the wetlands along the St.
Mary's River.

Kairesalo and Koskimies (1987) suggested that Stvlaria
lacustris L. migrated between the sediments and the
vegetation, overwintering in the sediments and returning to
the vegetation in early June. The data from the Quanicassee
marsh partially support their suggestion. Stylaria were
abundant in the vegetation on July 13, August 10, and
October 7 of 1989, and August 10, 1990 (Figure 7). They
were present in low densities on June 8 and October 6, 1990,
but were not found in the April and December, 1990,
vegetation samples. This provides evidence that Stylaria
migrate onto the macrophytes early in the summer. However,
Stylaria were not collected from the marsh sediment. If
Stylaria overwinter there, they must move deeper than 15 cm
into the sediment, or sampling was inadequate to detect
them.

Oligochaetes and chironomid larvae in the Quanicassee

marsh vegetation community were often found associated with

102

g. americanus. Early in the growing season these groups
were on the macrophyte stems, associated with the
periphyton. Krecker and Lancaster (1933) reported finding
over 15,000 invertebratesm‘2 of substratum covered by
Scirpus, with most of the invertebrates being chironomid
larvae found on the plants. Smock and Stoneburner (1980)
documented a correlation between greater density of
chironomids and oligochaetes on wetland macrophytes and
increasing decomposition of the vegetation. This
correlation was probably related to either increased diatom
density (Fairchild 1981) or increased microbial growth
(Beckett et al. 1992). The number of Chironomidae and
Oligochaeta found inside the cells of g. americanus in the
Quanicassee marsh also increased with increasing macrophyte
decomposition. These taxa were very rarely found inside
green, growing vegetation, but as the vegetation began to
yellow, greater numbers were found inside plant cells; the
highest numbers were found in the most decomposed vegetation
(personal observation).

Oligochaetes in the Quanicassee marsh vegetation
reached a maximum mean density of 15,400-m?2 on July 13,
1990 (Figure 5A). This density is within the maximum
abundance of 13,000 to 21,000 oligochaetes 111'2 reported by
Kairesalo and Koskimies (1987), but the peak in that study
occurred in early June, rather than in mid-July.

The high density of Chironomidae larvae on July 13,

1990, Quanicassee marsh vegetation community (12,000°m‘2,

103

Figure 11A) was due to the presence of large numbers of very
tiny larvae in Gerking-Mittelbach samples. Chironomidae
abundance on this date was probably underestimated, since a
mesh size of 250 um was used. The tiny larvae would have
been lost if they had not been entangled in mats of algae.
Duffy and Batterson (1987) found that up to 16% of
chironomid abundance could be lost using 250 pm mesh.

The large numbers of tiny Chironomidae larvae on July
13, 1990, indicate recruitment of another generation into
the population. Thus, emergence for one or several of the
more abundant species of chironomids in the Quanicassee
marsh had taken place in the months before this, when the
density of chironomid larvae was low (Figure 11A). There
may also have been emergence and recruitment of young into
the population in the late summer and/or fall (Figure 11A).
Judd (1953) reported that the emergence of various
chironomid species occurred throughout the spring, summer,
and fall in the Dundas Marsh, Lake Ontario. Many species
exhibited maximum emergence periods in May and/or August
(Judd 1953).

Judd (1953) collected quite a few more species of
Diptera emerging from the Dundas marsh, including species in
the families Tipulidae and Culicidae. While very few
Diptera other than Chironomidae and Ceratopogonidae were
collected in the Quanicassee marsh (Table 4), there may have

been other species in the dense beds of cattail, Typha

104

latifolia L. No samples were taken in these cattail beds
due to the density of the vegetative growth.

Oligochaetes in the marsh vegetation samples were often
in much better condition than those in sediment samples.
Oligochaetes in the sediment samples were more likely to be
Tubificidae (Figure 26). The Tubificidae were more fragile
than the Naididae that often dominated the vegetation
samples, and were more likely to be fragmented. Therefore,
Oligochaeta and Tubificidae densities in the sediment were
likely overestimated, especially the large Branchiura. The
biomass estimates, which were based on mean fragment size,
should be more accurate. Oligochaete biomass in the
sediments was greatest on June 8, 1990, with 1,100 mg-m‘2
(Table 6). Nalepa and Quigley (1983) reported 1,005 mg'm‘2
of oligochaete biomass in the 10 to 15 m depth of Lake
Michigan in 1977, but they found twice this biomass in the
same area in 1976.

Nematoda were much more abundant in the Quanicassee
marsh sediment than in the vegetation (Figures 5A and 25A).
They reached a mean density of 24,200-m‘2 (Figure 25A), with
a mean biomass of 14 mg-m‘2 on July 13, 1990 (Table 6).
Nalepa and Quigley (1983) reported Nematoda densities ten
times greater than this from the 11 m depth of Lake
Michigan, where Nematoda dominated the abundance and biomass
of the meiobenthos. Nematoda reached mean densities of

200,000-m‘2 (1976) to 3oo,ooo~m-2 (1977), with a biomass of

105

150 mg-m'2(1977) to 215 mg-m‘2 (1976) (Nalepa and Quigley
1983).

The greatest density of Tardigrada in the Quanicassee
:marsh sediment, 3,200-m‘2 (Table 6), was similar to the
lower numbers reported from Lake Michigan sediments.
Tardigrada were collected from the sediments of Lake
Michigan at densities of 1,000-m'2 to 4,300-m‘2 (Nalepa and
Quigley 1983). Up to 320,000 tardigradesm‘2 were present
during one year, however (Nalepa and Ouigley 1983). At the
Quanicassee marsh, the peak density of 26,800
tardigrades-m?2 occurred in the vegetation community on
December 13, 1990 (Table 3, Figure 3).

Nalepa and Quigley (1983) observed that the Tardigrada
were more abundant in the deeper areas they sampled, and
speculated that the tardigrades preferred the colder
temperatures. The presence of Tardigrada in samples from
the Quanicassee marsh also appeared to be inversely related
to water temperature: Tardigrada were present in 1990
samples from April through June and October through
December. Many Tardigrada in the December samples were
observed to be carrying egg sacs.

Caenis latipennis and Q. amigg were the two most
abundant species of Ephemeroptera in the emergent wetlands
near Quanicassee. These species were common and abundant in
both the vegetation and sediment communities (Figures 15A
and 28B). The Caenis are listed as sprawlers on the

sediment, and are classified as collector-gatherers and/or

106

scrapers in Merritt and Cummins (1984). These nymphs are
fair swimmers, and were likely exploiting the abundant
periphyton growth on the macrophytes, which would account
for their presence in both communities. These Caenis
species overwinter as nymphs in association with aquatic
detritus. The nymphs are apparently able to withstand
freezing temperatures, since most areas of the Quanicassee
marsh probably freeze down to the sediment. Middle instar
g. latipennis nymphs were collected on April 19, 1990,
indicating their ability to overwinter (Figure 15A). The
Caenis probably had emerged from the Quanicassee marsh by
August, judging from nymphal size and the presence of exuvia
in certain samples. The fall (September/October) caenid
abundance peak (Figures 15A and 28B) was composed of many
small, and therefore early instar, nymphs. Judd (1953)
reported that the species of Caenis present in the Dundas
Marsh emerged from June through early September, with the
peak emergence in mid-July.

No other Ephemeroptera were abundant, and only two
other genera were collected. Judd (1953) also found that
the Ephemeroptera in the Dundas Marsh were mainly Caenis.
The gill covers of the Caenis nymphs may have been one
factor which allowed them to survive in the Quanicassee
marsh. Siltation and sediment resuspension were high in
parts of this marsh at all times during the year. Turbidity
was high throughout the entire marsh during the spring,

however, due to sediment resuspension from wave action and

107

the spawning of carp (Q. car io; V. Brady pers. observ.).
The emergent vegetation (Scirpus and Typha) reduced wave
action to such an extent during the summer that the marsh
was effectively divided into nearshore and offshore zones.
McNabb and coworkers (pers. comm.) discovered that the
nearshore zone in the Quanicassee marsh had high water
clarity (turbidity <1 NTU), while the offshore zone had low
clarity (turbidity z 50 NTU). The transition between the
two water types occurred quite sharply between 300 and 400 m
from shore (McNabb et al. pers. comm.). The gill covers
possessed by the Caenis species would have prevented silt
from clogging their gills, while also offering physical
protection against abrasion.

The Caenis species appeared less abundant at greater
water depths (Figure 15B). However, the few dates on which
depth exceeded 50 cm occurred during July (Figure 35A), when
very few Caenidae were collected at any depth (Figure 15A).
No relationship emerged when Caenis abundance was graphed
against distance from shore. This indicates that turbidity
due to sediment resuspension was not a problem for the
Caenis, since samples in 1990 were taken out to nearly 600 m
from shore. At least three of the five vegetation and
sediment samples collected on each date were taken within
the highly turbid offshore zone during 1990.

However, for Ishnura verticalis Say (Odonata:
Coenagrionidae) there apparently was a relationship between

abundance and distance from shore (Figure 14B). 1.

108

verticalis was abundant at all sampling locations at the
1989 site, which was within the nearshore, clear water, zone
(Figure 148). The offshore zone began approximately 400 m
from shore at the 1990 site, just offshore of a very dense
I. latifolia bed. ;. verticalis was much less abundant
beyond 400 m from shore (Figure 148). Since two-thirds of
the samples in 1990 were collected from 400 m and beyond,
this may account for the difference in abundance of ;.
verticalis between the two years.

;. verticalis may not have been sensitive to the
increased turbidity, per se. L. verticalis is dependent on
dense stands of macrophytes (Duffy and Batterson 1987), and
macrophyte density, especially submergents, decreased beyond
400 m from shore in the Quanicassee marsh (Batterson et al.
1991). Decreased macrophyte density allowed greater wave
action in the marsh, the cause of the high turbidity. The
water movement itself may have been affecting the nymphs, or
they may have been subject to increased fish predation in
areas of lower density vegetation. The factor(s)
influencing the distribution of L. verticalis need further
investigation.

;. verticalis represented the Odonata almost
exclusively in the Quanicassee marsh (Table 4). Judd (1953)
found more Anisoptera and Enallagma species, especially
Enallagma ebrium, emerging from the Dundas marsh on Lake
Ontario. ;. verticalis was present in the Dundas marsh, but

only in very low numbers (Judd 1953). Adult dragonflies

109

were often seen flying about the Quanicassee marsh, but only
three nymphs were collected during the two year study. The
Anisoptera nymphs may have been living in the stands of I.
latifolia present at both sites. These cattail beds were
very dense, and were not sampled.

(The isopod Asellus forbesi Williams was present only in
the samples taken nearest the shore at the 1990 site (Table
3). This nearshore area was protected from wave action by a
large bed of I. latifolia, allowing detritus particles and
organic muck to accumulate. Detritus did not build up
anywhere else samples were taken in the marsh, due to the
constant wave action.

Aquatic mites were often more abundant in the sediment
than the vegetation community (Figures 5B and 25B). Some
mites hunt by standing on the sediment with forelegs raised,
waiting for prey to swim past (Smith 1991). Other mites are
fast swimmers, pursuing their zooplankton prey, while still
others eat Chironomidae larvae (Smith and Cook 1991).
Immature mites also undergo metamorphosis in the sediments
(Smith and Cook 1991). The mites in the Quanicassee marsh
were probably also hunting or waiting for hosts while
clinging to the vegetation, thus accounting for their
presence in the vegetation community. Krecker and Lancaster
(1933) found aquatic mites associated with Potamogeton and
Cladophora, but not Scirpus; Potamogeton was present in

protected locations at both sites.

110

The macroinvertebrate community in the Quanicassee
marsh was both numerically abundant and had high biomass on
occasion (Figures 5 and 24). Schneider, Hooper, and Beeton
(1969) estimated the macrobenthic standing crop in the
offshore areas of Saginaw Bay to be 3-4 g'm'z. The large
mayfly, Hexagenia, disappeared from Saginaw Bay since that
1956 study, but probably would not have inhabited the
shifting sands of the emergent marsh. However, the
macroinvertebrate biomass in the vegetation and sediment of
the Quanicassee marsh during the summer and fall was close
to the 3-4 g-m'2 reported by Schneider et al. (1969) for
deeper areas of the Bay in 1956 (Figures 5B and 248). This
high macroinvertebrate biomass would make these marshes
particularly valuable as sources of food for higher trophic
levels.

There were 49,700 macroinvertebrates-m‘2 associated
with the Quanicassee marsh vegetation on December 13, 1990
(Figure 5A), with a calculated mean weight of 1,500 mg'm‘2
(Figure 5B). These numbers provide a better sense of the
macroinvertebrate abundance the marsh supported when they
are converted to larger areas of the emergent marsh. Based
on these estimates, every 0.5 km2 of emergent marsh
vegetation along the southeastern shore of Saginaw Bay
supported an average of 12.4 billion macroinvertebrates, and
a macroinvertebrate biomass of 375 kg, on December 13, 1990.
There were 7.6 billion macroinvertebrates-0.5 km‘2 on July

13, 1990, while in early October of 1989, the macro-

111

invertebrate biomass in the vegetation community was around
180 kg-o.5 km-Z.

The Quanicassee marsh sediment community supported an
even greater macroinvertebrate abundance and biomass during
the summer. There were an estimated 12.2 billion
macroinvertebrates 0.5 km"2 in the sediment on July 13,
1990, while on July 13, 1989, macroinvertebrate biomass was
about 575 kg'0.5 km‘z. These numbers suggest that the
wetland areas of Saginaw Bay may provide fish with an
important source of food, since yellow perch (Egrga
flavescens Mitchill), as well as many other fish species,

feed on wetland macroinvertebrates (e.g. Clady 1973).

Crustacean Zooplankton

The crustacean zooplankton community in the Quanicassee
marsh vegetation reached its maximum abundance, approaching
250,000-m‘3, on October 27, 1989 (Figure 17). Watson and
Carpenter (1974) reported a maximum of 324,000
zooplankton-m‘3 in Saginaw Bay during August and September.
Watson and Carpenter (1974) found that Cladocera were more
abundant than Copepoda or Ostracoda in plankton tows in
Saginaw Bay, as was the case for the Quanicassee vegetation-
associated zooplankton community (Figure 17). The Saginaw
Bay biomass peak was estimated as only 800 mg-m‘3 AFDW
(Watson and Carpenter 1974), while the marsh zooplankton
community reached a peak of 15,000 mg-m‘3 due to the larger

size of the zooplankton in the marsh vegetation (Figure 18).

112

Clearly, the marsh supports a much higher standing crop of
zooplankton than does the open bay.

The zooplankton community in the emergent wetlands
associated with the st. Mary's River was also dominated by
Cladocera (Duffy and Batterson 1987). Many of the same
species present in that wetland were present in the
vegetation community of the Quanicassee marsh, but were
generally an order of magnitude more abundant in the St.
Mary's wetland (Table 9). The dominant Cladocera species in
the emergent wetlands of the St. Mary's river mouth delta
were A. harpae, Q. sphaericus (the most abundant), E.
lamellatus, and Q. serrulatus (Duffy and Batterson 1987).
These species were also very abundant in the Quanicassee
marsh vegetation community, along with A. uadran ularis, Q.
rectirostris, Q. megalops, Q. crystallina, and Q. vetulus
(Table 5, Figure 19).

Q. sphaericus reached the greatest abundance of any
Cladocera in the Quanicassee and St. Mary's River marshes
(Duffy and Batterson 1987). Q. sphaericus may have been
significantly underrepresented in samples from the
Quanicassee marsh. This species is very small, and a 250 um
sieve was used with all vegetation and sediment samples. Q.
sphaericus, while associated with the littoral zone, is a
water column resident (Fairchild 1981). This explains its
abundance in both Gerking-Mittelbach and sediment core
samples (Table 9), since both types included the water

column in samples.

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114

A. guadrangularis is a littoral zone resident which, as
of 1984, had not been reported from Lake Huron (Table 9,
Balcer et al. 1984). It reached a mean abundance of nearly
37,000'm.‘3 in the Quanicassee marsh sediment community,
however (Table 9), and made up approximately 25% of the
sediment zooplankton community biomass on two dates (Figure
34). This species is associated with littoral zone
sediments and may even burrow (Dodson and Frey 1991), making
it unlikely to be captured in plankton tows.

g. lamellatus is another littoral zone resident, one
which climbs on macrophytes (Dodson and Frey 1991). Samples
from the Quanicassee marsh vegetation provide evidence of
depth/distance from shore correlations with the abundance of
this species (Figure 21). The highest abundances of E.
lamellatus occurred in the midrange of water depths sampled
(Figure 21A), and near the middle distances from shore
(Figure 218). g. lamellatus grazes on periphyton (Fairchild
1981), but the periphyton community was not well-developed
on g. americanus stems in the nearshore areas due to the
frequent seiches (Batterson et al. 1991). Thus, E.
lamellatus would not be expected to be as abundant in the
shallower areas closer to shore. Possible explanations for
the decreasing abundance of E. lamellatus with increasing
water depth and distance from shore include 1) that this
species, like L. verticalis, was associated with dense
stands of macrophytes. Macrophytes were generally sparser

beyond 400 m in the Quanicassee marsh. Or 2) E. lamellatus

115

abundances were inversely correlated with turbidity or wave
action, which were much higher in the offshore portion of
the marsh (McNabb et al. pers. comm.).

Highest abundances for g. crystallina, on the other
hand, appeared to be shifted toward deeper water and greater
distances from shore in the Quanicassee marsh (Figure 22).
g. crystallina is largely confined to the littoral zone,
where it attaches to macrophytes using a cervical gland
(Fairchild 1981). From this fixed position, g. crystallina
filter-feeds on phytoplankton, rather than grazing
periphyton like most other littoral Chydoridae (Fairchild
1981). s. crystallina had low abundances in water depths
less than about 22 cm, but was abundant in water depths
greater than 35 cm (Figure 22A). g. crystallina abundance
was also correlated with distance from shore at the 1989
site (Figure 228). This was not true at the 1990 site
(Figure 228), where the mean depth was generally greater
(Figure 358). s. crystallina may be limited to depths
greater than the water level change of :20 cm of the
commonly occurring seiches (Batterson et al. 1991), or to
depths at which it can migrate out with the outgoing water
during larger seiches.

Ostracoda generally dominated the abundance and biomass
of the Quanicassee marsh sediment zooplankton community.
(Figures 31 and 32). Ostracoda reached densities around
130,000'm'3 in the sediment at both the 1989 and 1990 sites

(Figure 31), much higher than their numbers in the

116

vegetation community (Figure 17). Duffy and Batterson
(1987) found even greater numbers in the St. Mary's River
marsh, with 201,000 ostracods-m‘3 (Table 9). As with many
of the smaller Cladocera and Copepoda, ostracod densities in
the Quanicassee marsh may have been underrepresented due to
the use of 250 um mesh. Ostracoda were commonly collected
in Gerking-Mittelbach samples, although they were not as
abundant in the vegetation community (Table 5).
Mbahinzineki et al. (1991) found that at least some littoral
ostracods climb on macrophyte vegetation to graze the
periphyton community, retreating to the sediments as a
refuge from fish predation.

The mean filtering rates of several Cladocera species
were obtained or calculated from the literature to provide a
rough estimate of the filtering capacity of the most
abundant Cladocera present in the Quanicassee marsh. The
Cladocera were most abundant in the Quanicassee marsh
vegetation community on October 27, 1989, and August 10,
1990. g. sphaericus was the principal filtering Cladocera
present on October 27, 1989 (Figure 19). (A. quadrangularis
and A. harpae were also abundant, but are periphyton grazers
(Fairchild 1981)). Lair (1989) calculated a mean individual
filtering rate of 403 u.l°hr'l for Q. sphaericus. There were
107,200 9. sphaericu5°mf3 on October 27 (Table 5), yielding
a filtration rate of approximately 1,040 l°day‘1. That is,
on this date g. sphaericus was capable of filtering all the

water in the marsh in one day.

raw.- _ 04-;- 'thb

 

117

§. crystallina, Simocephalus, and g. megalops were the
most abundant filtering Cladocera present on August 10, 1990
(Figure 19). The average individual filtration rate for g.
megalops was about 408 ul-hr-l (Lair 1989) . With 13,400 _<_:_.
megalop5°mf3 present on August 10 (Table 5), the calculated
filtration rate was 130 l'day‘l. The individual filtration
rates for g. crystallina and Simocephalus were calculated
from the general formula for Cladocera derived by Knoechel
and Holtby (1986):

F=ll.695L2'48

F = filtering rate in ml°ind.'1°day'1
L = Average length of Cladocera in mm

§. crystallina had a mean length of 1.038 mm on August 10,
giving a individual filtering rate of 12.8 ml-day‘l. There
were 30,700 g. crystallina-mf3jpresent on August 10 (Table
5), which yields an approximate filtering rate of

394 l-day‘l. Simoce halus, with an estimated average length
of 0.9 mm, had a calculated individual filtering rate of

9 ml°day'1. With 32,800 Simocephalus'm"3 present on August
10, their filtration rate was calculated to be 295 l-day'l.
Thus, a rough estimate of the filtration capacity of these
Cladocera on August 10, 1990, was 820 l day'l, or three-

fourths of the water in the marsh per day on this date.

SUMMARY AND CONCLUSIONS

The invertebrate community of a coastal marsh on
Saginaw Bay, Lake Huron, near Quanicassee, Michigan, was
sampled from July through October of 1989, and April through
December of 1990. Vegetation-water column, sediment core-
water column and aquatic dip net samples were taken between
150 and 600 m from the shore in water depths averaging 30 to
60 cm. The emergent marsh was characterized by the emergent
bulrush, Scirpus americanus Pers., growing on a substrate
predominately composed of shifting sand, rather than the
organic muck typical of many emergent marshes.

The macroinvertebrate community in the vegetation was
represented by 54 species of insects and 11 other orders of
macroinvertebrates. Macroinvertebrates in the marsh
vegetation reached their greatest abundance and biomass on
December 13, 1990, with 50,000 individuals-m’2 and 1.5 gm"2
of biomass.

This community was dominated by Chironomidae,
Oligochaeta, and the Ephemeroptera genus Caenis. Chironomid
larvae were the most abundant insects, making up 80% of all
insects collected on several dates. They reached mean
densities of 12,000'm‘2 on July 13, 1990, in the vegetation

community. Chironomid larvae, along with oligochaetes and

118

 

 

119

nematodes, were quite numerous in the cells of senescent g.
americanus vegetation.
In addition to the Chironomidae, the Ephemeroptera,

Caenis latipennis Banks and Caenis amica Hagen, were among

 

the more common and abundant insects present in the marsh.
However, taxa that were more unique to this community
included the Coleoptera, Hemiptera, Lepidoptera, and the
Odonata, Ishnura verticalis Say, which are all associated
with aquatic macrophytes. L. verticalis was less abundant
in the marsh beyond 400 m from shore. This area of the
marsh was in the highly-turbid offshore zone, with lower
macrophyte density and increased wave action. The
correlation between ;. verticalis abundance and distance
from shore needs further investigation.

The oligochaetes in the vegetation community were
represented mainly by Naididae, with the genus Stylaria
present only in the vegetation. Oligochaeta reached mean
densities of 15,500-m‘2 in the vegetation community on July
13, 1990.

The macroinvertebrate community in the marsh sediment
was less diverse, probably because of the instability of the
marsh sediment. Sixteen species of insects and 9 other
orders of macroinvertebrates were represented in the marsh
sediment. The sediment community had its highest density
and biomass during July, with 48,900 macroinvertebrates'm‘2
on July 13, 1990, and a biomass of 2.3 gm‘2 on July 13,

1989. The sediment macroinvertebrate community consisted

120

mostly of Chironomidae, Oligochaeta, and Nematoda, with the
chironomids and oligochaetes making up most of the
community's biomass. Oligochaetes in the sediments reached
a maximum mean biomass of 1,100 mg-m‘z, and a density of
10,000 m'2, on June 8, 1990, with most of these being
Tubificidae. The sediment macroinvertebrate community
reached a mean weight 1.5 times greater than the maximum
mean weight of the macroinvertebrates in the vegetation
community.

The Quanicassee marsh supported 7.6 billion macro-
invertebrates in every 0.5 km2 area of emergent vegetation,
and every 0.5 km2 area of sediment supported 12.2 billion
macroinvertebrates on July 13, 1990. The macroinvertebrate
biomass in every half square kilometer of marsh sediment
averaged 575 kg on July 13, 1989.

The most abundant crustacean zooplankton in the
Quanicassee marsh were Acroperus harpae Baird, Alggg
quadrangularis (0.F. Muller), ggmptocercus rectirostris
Schodler, Ceriodaphnia, Chvdorus sphaericus (0.F. Muller),

Eurycercus lamellatus (0.F. Muller), Sida crystallina (0.F.

 

Muller), Simocephalus, Acanthocyclops vernalis Fischer,
Eucyclops agilis Koch, Harpactacoida, and Ostracoda.
Cladocera dominated the abundance and biomass of the
vegetation zooplankton community, but the sediment
zooplankton community was dominated by the Ostracoda.

g. sphaericus reached the highest abundances of any

zooplanktor in either the vegetation or sediment

121

communities. S. crystallina dominated the vegetation
community biomass, while Ostracoda dominated the sediment
zooplankton biomass. S. crystallina abundance was
positively correlated with water depths greater than 35 cm.
E. lamellatus abundance, on the other hand, seemed to be
related more to distance from shore than water depth, and
was greatest between 250 and 400 m from shore. The
abundance correlations of both of these Cladocera need
further investigation.

The zooplankton in the Quanicassee marsh sediment
reached a mean abundance of 356,700-m"3 on October 27, 1989,
with a biomass of 5 g-m‘3. Zooplankton community abundance
in the vegetation on this date was nearly 250,000
zooplankton°m'3. Zooplankton biomass in the vegetation was
greatest on August 10, 1990, with 15.1 g°m‘3. The
macroinvertebrate and zooplankton communities in the
vegetation and sediment of the Quanicassee marsh probably
serve as an important food resource for fish inhabiting

Saginaw Bay.

APPENDIX

2
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Table A-2. Chironomidae present in vegetation and sediment

samples on June 30 (preliminary sampling) and

July 13, 1989, in a Saginaw Bay, Lake Huron,

coastal marsh.

VEGETATION SEDIMENT.
CHIRONOMIDAE* MEAN NUMBER MEAN NUMBER
PER M2 PER M2

Chironominae
Chironomus 13 2306
Cladopelma laccophila group 0 28
Cladotanytarsus manous group 14 2417
Cladotanytarsus vanderwulpi gr. 0 28
Cryptotendipes O 48
Dicrotendipes 4 214
Einfeldia species group A 27 83
Einfeldia species group B 0 110
Einfeldia species group C 0 359
Endochironomus 62 207
Glyptotendipes species group A 7 O
Glyptotendipes species group B 7 0
Glyptotendipes species group C 64 48
Microchironomus O 55
Parachironomus arcuatus group 7 O
Paracladopelma O 483
Paratanytarsus species 71 407
Polypedilum 17 28
Tanytarsus 98 1340
Virgatanytarsus O 28
Orthocladiinae
Corynoneura 174 O
Cricotopus bincinctus group 7 0
Cricotopus sylvestris group 1564 249
Cricotopus species 17 O
Orthocladius 13 O
Orthocladius 5. str. 34 0
Thienemanniella 20 O
Tanypodinae
Ablabesmyia 7 ’55
Procladius (Holotanypus) 7 55
Tanypus 34 83

 

* Identification references: SimpsOn and Bode 1980, and
Wiederholm 1983.

125

 

 

 

 

 

 

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LITERATURE CITED

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