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EFFECTS OF DIKING AND PLANT ZONATION ON
INVERTEBRATE COMMUNITIES OF LAKE ST. CLAIR
COASTAL MARSH ES

presented by
COLE DANIEL PROVENCE

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5/08 K;lProj/Acc&PresICIRC/DateDue.indd

EFFECTS OF DIKING AND PLANT ZONATION ON INVERTEBRATE
COMMUNITIES OF LAKE ST. CLAIR COASTAL MARSHES

By

Cole Daniel Provence

A THESIS
Submitted to
Michigan State University
In partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
Fisheries and Wildlife

2008

ABSTRACT

Effects of Biking and Plant Zonation on Invertebrate Communities of Lake St.
Clair Coastal Marshes

By

Cole Daniel Provence
Invertebrate communities from emergent plant zones common to two diked and two
undiked marshes were compared during July 2006, in order to document differences
in the potential prey base of avian fauna of Lake St. Clair deltaic marshes.
Invertebrate samples were taken with a 0.5 mm D-frame dip net from the outer 1-2 m
edge of the emergent plant zones dominated by Schoenoplectus acutus, T ypha
angustifolia, or the invasive form of Phragmities australis. Equal effort consisting of
3 minutes of sweep net collecting per sample was expended in order to quantify catch
per unit effort (CPUE) differences in numbers between diked and undiked marshes
for each plant zone. A total of 109,649 invertebrates were collected: 93,959 from
diked marshes (3,758 per sample, N=25) and 15, 690 from undiked marshes (541 per
sample, N=29). Thus, seven times more invertebrates were collected per sample from
diked marsh samples than were collected from undiked samples (p=0.03, 2-way
AN OVA) suggesting that the prey base for breeding waterfowl and other invertebrate
predators is greater in diked marshes than in undiked marshes. I also tested Shannon’s
Diversity Index, evenness, and taxa richness. Shannon’s Diversity and evenness were
not significantly different, but taxa richness (p=0.05) was significantly greater in
diked marshes compared to undiked marshes. Sorensen Similarity Index revealed that
77% of taxa were similar between diked and undiked marshes. There was no

significant difference in the invertebrate community caused by plant zone or location.

To Everyone Who Made This Possible

iii

ACKNOWLEDGEMENTS

I would like to thank my major professor, Dr. Thomas M. Burton, for his
guidance during my M.S. program and for advice, suggestions, and critiques that
greatly improved this thesis. I would also like to thank him for his willingness to take
me as a graduate student and his many efforts to secure financial support for me. I
also thank the other two members of my graduate committee, Dr. Richard W. Merritt,
and Dr. R. Jan Stevenson, for guidance on my M. S. program and thesis.

I would especially like to thank Dr. Patrick Brown and Mike Monfils of the
Michigan Natural Feature Inventory for providing financial support for field work,
student labor to help process invertebrate samples, and for allowing me to piggyback
the design of my project on their project on avian use of diked and undiked marshes.
I would also like to thank Edi Sonntag who listened to my unending questions and
provided encouragement when I needed it. Thanks are due to Diana Lutz for her
assistance with processing invertebrate samples and encouragement and to Chris and
Brenda Prachiel, Seth Hunt, Julie Heinlein, and Holly Campbell for friendship and for
providing feedback on my ideas and questions.

I would also like to extend my appreciation to Ernie Kafcas and John Schafer
of the Michigan Department of Natural Resources (MDNR) for allowing me to use
their equipment and providing access to the research sites. This project was supported
by the Federal Aid in Restoration Act under Pittman-Robertson project W-l47-R to
the Michigan Natural Features Inventory through the MDNR Wildlife Division.

Partial Funding was also provided by the United States Fish and

iv

Wildlife Service through the Upper Mississippi River and Great Lakes Region Joint

Venture and by assistantship support from Michigan State University.

Table of Contents

List of
Tables ............................................................................................. vii
List of
Figures ........................................................................................... viii

Effects of Biking and Plant Zonation on Invertebrates Communities of Lake St.
Clair Coastal Marshes

Introduction ................................................................................... 1
Methods ....................................................................................... 4
Study Area ........................................................................... 4
Field Sampling ...................................................................... 8
Laboratory Identification ......................................................... 10
Water Chemistry .................................................................. l 1
Statistical Analysis ................................................................ 11
Results ........................................................................................ 12
Water Chemistry .................................................................. 12
Invertebrate Community Parameters between Diked and Undiked
Marshes ............................................................................. 13
Comparison of Invertebrate Community Parameters in Diked and Undiked
Marshes ............................................................................. 15
Effects of Plant Zonation on Invertebrate Community Parameters... ......35
Functional Feeding Groups ....................................................... 39
Functional Habitat Groups ....................................................... 39
Invertebrate Frequency ........................................................... 43
Discussion ................................................................................ 46
Conclusion .......................................................................... 51
Appendix .......................................................................................... 55
Literature
Cited .............................................................................................. 73

vi

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

List of Tables

Summary Table of Mean (:tStandard Error) Invertebrate Community
Characteristics from Diked and Undiked Marshes and Schoenoplectus,
T ypha, and Phragmites Zones ................................................... 3 8

Sorensen Similarity Index with Number of Similar Taxa (% similarity) for
Diked and Undiked Marshes from Schoenoplectus, T ypha, and Phragmites
zones ................................................................................ 41

Total Number per Sample and Percent Total Catch of Dominant taxa in
Diked and Undiked Marshes in Schoenoplectus, T ypha and Phragmites
Zones ................................................................................ 42

Mean Invertebrate Relative Catch >1% (iStandard Error) in Diked and
Undiked Marshes .................................................................. 47

Percent Invertebrate Frequency (>50%) from Diked and Undiked Marshes
in Schoenoplectus, T ypha, and Phragmites Zones ............................ 53

vii

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

List of Figures

Location of study areas in the St. Clair River Delta. Diked marshes are
indicated with a * (figure from Herdendorf et a1. 1986; they adapted it
from Raphael and J aworski 1982) .............................................. 17

Mean Number per Sample (:t Standard Error) in Diked and Undiked
Marshes from Schoenoplectus, T ypha, Phragmites zones. * The total
number of invertebrates per sample (p=0.03) were significantly greater in
diked wetlands ..................................................................... 23

Hyalella total number per sample (i standard error) in diked and undiked
Schoenoplectus, Typha, and Phragmites zones ............................... 28

Caem's total number per sample (istandard error) in diked and undiked
Schoenoplectus, T ypha, and Phragmites zones ................................ 29

Naididae total number per sample (istandard error) in diked and undiked
Schoenoplectus, T ypha, and Phragmites zones ............................... 3O

Gastropoda total number per sample (istandard error) in diked and
undiked Schoenoplectus, T ypha, and Phragmites zones ..................... 31

Tanytarsini total number per sample (:tstandard error) in diked and undiked
Schoenoplectus, Typha, and Phragmites zones ............................... 36

Crangonyx total number per sample (:t standard error) in diked and undiked
Schoenoplectus, Typha, and Phragmites zones ............................... 37

Percent relative catch per sample and * percent total number per sample
(>5%) of invertebrates in each of the three vegetation zones in diked and

undiked Marshes .................................................................. 43

Percent functional feeding groups from diked and undiked
Schoenoplectus, T ypha, and Phragmites zones ............................... 50

Percent functional habitat groups from diked and undiked Schoenoplectus,
Typha, and Phragmites zones .................................................. 51

viii

INTRODUCTION
There are roughly 217,000 hectares of Great Lakes coastal marshes (SOLEC

2004). Marshes in and along connecting waterways are considered to be Great Lake
coastal marshes (SOLEC 2004, Albert 2001, Tsanis et al. 1996, Schloesser 1988). The St.
Clair River and Lake St. Clair form the northern part of the connecting waterway
between Lake Huron and Lake Erie (Thomas et al. 2006). The more than 13,500 hectares
of Lake St. Clair marshes are classified as Great Lake coastal wetlands and roughly
13,146 hectares (96%) of these marshes occur in the delta where the St. Clair River
empties via distributary channels into Lake St. Clair (Thomas et al. 2006, SOLEC 2004).

Coastal marshes are important habitat for many fish (J ude and Pappas 1992, French
III 1988), amphibians (Herdendorf et al. 1986), birds (Prince et al. 1992) and mammals
(De Szalay and Cassidy 2001, Herdendorf 1987). Aquatic invertebrates are important
food sources for many of these vertebrates (Herdendorf et al 1986, French III 1988, Krull
1970). Recent studies have described invertebrate communities of Great Lakes marshes
and related their occurrence to abiotic and biotic factors including anthropogenic stress
(Burton et al. 2004, 2002, 1999, MacKenzie et al. 2004, Stricker et al. 2001 , Gathman et
al. 1999, Cardinale et al. 1998, Bedford 1992, Krieger 1992, McLaughlin and Harris
1990). These factors include temperature, depth and type of sediment, gradients in
geochemistry from the shore to the open lake, groundwater inputs, plant community
structure, short and long term changes in lake levels, fetch, and wave action (Burton et al.
2004, 2002, Stricker et al. 2001, Cardinale et al. 1998, Bedford 1992, Krieger 1992).

Most studies cited above have been conducted on riverine and lacustn'ne Great Lake

marshes and may not apply to the deltaic marshes that dominate Lake St. Clair. The

marshes in the St. Clair River Delta do not have the characteristic turbidity problems of
Green Bay or Saginaw Bay marshes because suspended sediment load is low in the Lake
Huron water that is transported by the St. Clair River into the marshes, the rapid
exchange of water between the river’s distributary channels and the marshes, and the
relatively low fetch and exposure to winds in Lake St. Clair compared to marshes of the
five larger Great Lakes (Herdendorf et al. 1986). Regardless, there are few studies of the
invertebrate community in Lake St. Clair marshes. Instead, most invertebrates studies
have been focused on deeper waters of Lake St. Clair (Zanatta et al. 2002, Edsall et al.
2001, 1988, French III 1988, Nalepa and Gauvin 1988, Bricker et al. 1976) or in the St.
Clair and Detroit Rivers (Davis et al. 1991, Ciborowski and Corkum 1988, Thornley
1985)

Lake St. Clair marshes have been altered by many different human activities,
including diking (Albert 2001, Herdendorf 1987, Herdendorf et al. 1986, Derecki 1985,
McCullough 1985, Quinn 1985). Dikes are used to manipulate water levels for waterfowl
use and hunter access (Albert 2003, Jude and Pappas 1992, Prince et al. 1992, Herdendorf
1987, Herdendorf et al. 1986). In undiked marshes, natural water levels fluctuate with
storm events and wave action (Quinn 1980) and as lake levels rise and fall seasonally and
from year to year. The natural water level fluctuations structure the plant and animal
communities along Great Lake marshes and lead to dynamic changes in these
communities as water levels change from lows to highs (Gathman et al. 2005, Burton et
al. 2004, 2002, Herdendorf 1987, Barton and Griffiths 1984).

Diking of coastal marshes has been shown to cause changes in invertebrate

(Mclaughlin and Harris 1990, Krieger 1992), fish (Jude and Pappas 1992), and plant

communities (Herrick and Wolf 2005, Thiet 2002). Stabilized water levels in diked
marshes lead to dominance by plants tolerant of deeper standing water like narrow leaved
cattail (Typha angustifolia), hard stem bulrush (Schoenoplectus acutus) and the common
reed (Phragmites australis) (Herrick and Wolf 2005, Thiet 2002, Herdendorf et al. 1986).
The invasive form of common reed, Phragmites australis (Cav.) Trin. Ex Steud has
invaded marshes throughout North America (Saltonstall et al. 2004). In the Great Lakes
region, there is a native, non-invasive form, Phragmites australis subsp. americanus that
is limited in distribution and rarely occurs in a monoculture (Saltonstall et al. 2004). The
invasive form of Phragmites australis is thought to be an import from Europe and is an
aggressive invader, particularly of disturbed marshes. Recently, several researchers have
documented the occurrence of the exotic Phragmites in Great Lake coastal marshes and
have examined its effects on wetland communities (Kulesza and Holomuzki 2006,
Herrick and Wolf 2005, Wilcox et al. 2003, Thiet 2002). Phragmites has been found in
Lake Erie (Wilcox et al. 2003, Thiet 2002, Herdendorf 1987), Lake St. Clair (Albert
2003, Herdendorf et al 1986), Lake Huron (Herrick and Wolf 2005, Albert 2003), and
Lake Michigan marshes (Herrick and Wolf 2005). In these studies, Phragmites has
replaced or altered native plant communities (Herrick and Wolf 2005, Thiet 2002) with
Typha communities being particularly susceptible (Wilcox et a1. 2003). In addition,
Phragmites has been shown to alter food webs in brackish-water marshes by altering
benthic microalgae and phytoplankton communities (Wainright et al. 2000). Negative
effects have also been documented for aquatic invertebrates (J ivoff and Able 2003,

Angradi et al. 2001) and fish (Raichel et al. 2003, Weinstein and Balletto 1999). Parsons

(2003), however suggested that Phragmites could have some positive benefits for nesting
birds.

The primary objectives of this study were to (1) test the hypothesis that invertebrate
community species composition, relative catch, richness, and evenness would differ
significantly between diked and undiked coastal marshes; (2) test the hypothesis that the
invertebrate parameters listed above would be affected by and correlated with plant
zonation in diked and undiked marshes: and (3) document differences in three plant zones
common to diked and undiked marshes in order to document changes in the potential
prey base for avian fauna in diked and undiked Great Lake coastal marshes.

METHODS
Study Area

The St. Clair River delta is formed in, along, and between distributary channels of
the St. Clair River where the river enters Lake St. Clair. It extends along the shoreline
away from these channels to form an arcuate wetland in areas where sediments are
carried by wind and currents. The St Clair delta is the largest complex of delta marshes in
the Great Lakes Basin (Herdendorf et al. 1986). The delta is connected to Lake Huron
and Lake Erie and the other Great Lakes via the St. Clair River-Lake St. Clair-Detroit
River connecting channel. While the delta shares characteristics with both Lake Huron
and Lake Eric, the greatest inputs come from Lake Huron (Thomas et al. 2006, Leach
1980). The Michigan, USA, side of the delta is approximately 16 km long and 24 km
wide (Albert 2003, Herdendorf et al. 1986). The delta is formed from eroded shoreline
sediments from Lake Huron (Thomas et al. 2006) and the sediments eroded from the St.

Clair River Channel by currents and ship traffic. Sandy sediments are generally carried

into bays by wave action and overlay glacial clays (Thomas et al. 2006). The deltaic
coastal marshes at the mouth of the river occupy 13,146 ha (SOLEC 2004) along the
distributary channels of the St. Clair River, in bays around the low lying margins of
islands between channels, and along the shoreline of Lake St. Clair extending away from
the St. Clair River in the USA. and Canada. The delta has been altered by residential
deveIOpment along the US. shoreline, on islands in the delta, and by dredging of
channels and movements of vessels along these channels to support commercial shipping
in the Great Lakes (Albert 2003, Ball et al. 2003, Derecki 1985, McCullough 1985,
Quinn 1985).

The study area was located in the St. Clair Flats Wildlife Management Area on
Harsen’s and Dickinson Islands (Figure 1). The St. Clair Flats is managed by the
Michigan Department of Natural Resources (MDNR). The two diked marshes were
located on Harsen’s Island. One of the undiked marshes was located in the Little
Muscamoot Bay area of Harsen’s Island near the Middle Channel and the other was
located in the Goose Bay and Mud Lake area of Dickinson Island between the Middle
and North Channels (Figure 1). Dickinson Island is the largest (approximately 1,200
hectares) naturally functioning wetland complex along Lake St. Clair (Herdendorf et al.
1986), and Little Muscamoot Bay is the only area along Harsens Island that has remained
an undiked wetland with natural water flow (Herdendorf et al. 1986). The undiked
marshes experience natural water level fluctuations caused by storm events, but generally
water levels remain stable during the months of June, July, and August (Albert 2001,
Herdendorf et al. 1986). Along the shoreline which experiences the most wave action,

Phragmr’tes has become the most dominant vegetation type and, in areas that are

protected from wave action, dense stands of Typha angustifolia often dominate.
Schoenoplectus acutus is the dominant bulrush type in the St. Clair delta and occupies
deeper water than either T ypha or Phragmites.

Diked marshes, located on Harsen’s Island, are separated into East and West units
(Figure 1) and are managed for migratory waterfowl hunting by the MDNR (Herdendorf
et al. 1986). Water levels are controlled and maintained by the MDNR at depths that vary
from year to year. During some years, water levels are maintained at high levels
throughout the year, as during this study, while in other years, water levels are allowed to
drop to expose large mud flats. Most diked marshes during this study were covered with
emergent plants, mainly Typha angustifolia, with channels out between stands to allow
boat access for hunters. These channels often contained dense growths of water-lily
(Nymphaea), yellow water-lily (Nuphar), hardstem-bulrush (Schoenoplectus acutus), and
submersed plants. Phragmites appeared to have colonized the diked marshes along the
edges of hunter access channels and in mud flats. To control Phragmites spread, MDNR
uses herbicides and controlled burns within diked marshes.

Both diked and undiked marshes in the St. Clair Flats were dominated by three
emergent plant zones: bulrush zones dominated by hardstem bulrush, Schoenoplectus
acutus, cattail zones dominated by T ypha angustifolia and Typha X glauca, and common
reed zones dominated by the invasive form of Phragmites australis (Albert 2001,

Herdendorf et al. 1986). Each of these zones in diked and undiked marshes was sampled.

 

  
      
   
   
  

 

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Figure 1. Location of study areas in the St. Clair River Delta. Diked marshes are
indicated with a * (figure from Herdendorf et al. 1986; they adapted it from Raphael and

Jaworski 1982).

Field Sampling

I selected sites based on two criteria: migratory waterfowl, wading birds, or other
wetland dependant birds were observed feeding on—site, or the site was within 10 m of the
randomly selected points used for bird counts (M. Monfils, pers.comm.). Placement of
invertebrate sampling areas near sites used for bird counts will allow invertebrate results
to be related to data on distribution of birds in the marshes collected by Mike Monfils and
his crew from the Michigan Natural Feature Inventory. The bird results were not part of
this thesis and correlations between bird and invertebrate distribution in the marshes will
be published separately. Since birds heavily used areas near the edge of the emergent
zones and the open water of the channels, invertebrate sampling was limited to sampling
the outer 1-2 m edges of emergent zones. In many places, the density of the vegetation, or
the lack of standing water in the middle of vegetation stands would have precluded
sampling far enough into the plant stand to avoid edge effects. In most Schoenoplectus
and Phragmites sites, I was able to sample at least 1 meter into the emergent zone. Sites
where MDNR had burned or applied herbicide to control Phragmites were not sampled.

Invertebrates were collected from July 10 to July 21, 2006 using a standard D—frame
dip net with 0.5-mm mesh net. I sampled invertebrates in July to allow the plant
community to fully develop and invertebrates to become larger, making it easier to
identify them (Burton et al. 2004, 1999, Uzarski et al. 2004, De Szalay and Cassidy 2001 ,
McLaughlin and Harris 1990). The net was swept through the water column in each plant
zone at the surface, above the sediments, and along plant stems for a period of 60 seconds
per replicate. At the end of 60 seconds, the contents of the net were placed into a whirl

pack with 95% ethanol and labeled as one of three replicates taken per sample. Even

though each replicate was sorted and picked separately, data from the three replicates per
sample were combined and treated as a single sample for statistical analyses. Thus, each
sample consisted of combined data from three 60 second sweeps or a total of 3 minutes of
dip net sweeps per sample. Sampling in three separate areas within a 2 meter radius of a
sample point and combining data from these 3 sweeps ensured a representative area was
sampled. The one minute of sweeping per replicate for 3 replicates per sample
standardized effort for each sample so semi-quantitative comparisons could be made in
terms of total catch and catch per unit effort (CPUE).

In diked marshes, 13 samples (39 replicates) from East Marsh and 12 samples (36
replicates) from West Marsh were collected (Figure 1). From undiked marshes, 18
samples (54 replicates) were collected from Dickinson Island and 11 samples (33
replicates) were collected from Little Muscamoot Bay (Figure l). I collected replicates by
making the midpoint of the front of the boat the point around which samples were
collected. From the mid-point, I collected one replicate left of the point, one replicate
right of the point, and one replicate straight ahead of the point. Initially, I planned to take
five samples from each of the three vegetation zones so that there would be a total of 15
samples (45 replicates) from each marsh, but I was limited in Little Muscamoot Bay, East
Marsh, and West Marsh by the number of available sites. While large areas of East and
West marshes were covered with Typha and Phragmites, they remained above the water
surface by forming dense floating islands. A minimum of three samples per vegetation
zone was collected from each of the four marshes. At Dickinson Island, I increased the
number of samples to six from each zone, based on the suggestions of Dr. Thomas

Burton and Dr. Patrick Brown to include samples from Mud Lake.

Laboratory Identification

In the laboratory, three invertebrate samples from each of three plant zones from the
two diked and two undiked marshes were completely picked and sorted. Since hundreds
of invertebrates were picked from each replicate of the diked wetland samples, picking
took many hours to complete. To speed up the process, the remaining replicates from the
diked marshes were first sieved through a 4-mm sieve to remove larger pieces of organic
detritus and then into a 250 micrometer sieve. The invertebrates picked from the larger
debris were added to the contents of the 250 micrometer sieve. The contents of the sieve
were then split into four sub samples using a Folsom plankton splitter. One sub-sample
was picked and the rest were discarded for the 16 samples collected from diked marshes
that were not completely picked. Fewer undiked samples were sub-sampled because they
were easier to pick than were diked marsh samples because of fewer invertebrates and
less debris per sample. Only five samples from undiked marshes were sub-sampled
compared to 16 samples from diked marshes. Samples were picked and sorted, under
10x magnification, to the lowest operational taxonomic unit (usually Family or Genus)
using a variety of taxonomic keys (Merritt and Cummins 1996, Thorp and Covich 1991,
Peckarsky et al. 1990, Burch 1982, Burch and Tottenham 1980, and Wiggins 1978).
Insects were assigned to functional feeding and functional habitat groups using Merritt
and Cummings (1996). The other invertebrates were assigned to feeding group and
habitat group using De Szalay and Cassidy (2001), Thorp and Covich (2001), Clifford

(1991) and Peckarsky et al. (1990).

10

Water Chemistry

Water chemistry was measured in the field between June 17 to August 2, 2006 from
sampling stations where invertebrates were collected and points where breeding bird and
shore bird surveys took place across all four marshes. Measurements were taken at mid-
depth at each site. Dissolved oxygen (D.O) (mg/L), salinity, specific conductivity (mS/L),
pH, and temperature (°C) were measured using a Hydrolab water quality probe (Hydrolab
Corporation, Austin, TX). Water depth was measured with a meter stick. Alkalinity (mg
C3CO3/L) was measured with a Hach Test Kit (Model AL—AP, Drop Count Titration),

and turbidity was measured in NTU (nephelometer turbidity units) with an Oakton T-100

Turbidimeter.

Statistical Analyses

The mean number of invertebrates per sample (istandard error) was calculated for
each plant zone sampled. The number of invertebrates for each of the three replicates was
summed to calculate total number per sample. Raw data for each sample was then
converted to relative catch (taxon total divided by total number of invertebrates collected
per sample) and percent frequency (number of times a taxon occurred in all replicates
divided by the number of total replicates per vegetation type). Invertebrates were only
reported as frequent if they occurred in >50% of replicates in any of the plant community
zones.

Community composition was evaluated by calculating percent relative catch of
taxa, taxa richness, Shannon’s diversity index (H ’), Simpson’s Evenness (J ’), Sorensen
similarity index, percent frequency of taxa, percent functional feeding group, and percent

functional habitat group. Percent functional feeding group and habitat group was the total

11

in each group of samples divided by the grand total of invertebrates for all samples per
zone. Functional feeding groups were restricted to predators, gatherer-collectors,
scrapers, shredders, piercers, and filterers. Functional habitat groups were restricted to
sprawlers, burrowers, clingers, swimmers, climbers, and skaters.

Total number of invertebrates per sample, Shannon’s diversity (H’), species
richness, Simpson evenness (J ’), and relative catch were determined for each marsh and
vegetation zone. To determine if wetland type or vegetation type had an effect on the
invertebrate community, I used a (PROC MIXED) two way analysis of variance
(AN OVA) (SAS Version 9, SAS Institute Inc., Cary, NC, USA). Bonferroni t-tests were
used with pair-wise comparisons to determine whether differences among the three plant
community types were statistically different. A majority of data were LOG transformed
to correct for variance within the data. Percent invertebrate frequency, percent functional
feeding groups, and percent functional habitat groups were also used to determine
whether differences occurred. Location was also tested for statistical significance using
location (wetland) and plant*location (wetland) as random effects in the Proc Mixed
code. Results were considered significant at p<0.05 but were also reported as marginally

significant if p<0. 1 0.
RESULTS

Water Chemistry

Because water chemistry was collected at different dates, times of day and only
once per site, statistical analysis was not possible. The data were used to broadly
characterize the sites where invertebrates were collected and marsh birds were feeding.

Samples were collected from similar depths from all plant zones and diked and undiked

12

marshes (29-39 cm deep in diked marshes; and 31-42 cm deep in undiked marshes). At
the time of collection, water temperature ranged from 25.3-25.6°C in diked marshes and
from 24.5-24.9°C for undiked marshes. Alkalinity was lower in undiked marshes ranging
from 112-119 mg CaCO3/L compared to diked marshes at 178-190 mg CaCO3/L.
Dissolved oxygen levels were higher in undiked marshes at 5.3-6.4 mg/L than in diked
marshes at 3.9-4.6 mg/L. Even though water was slightly cooler, dissolved oxygen was
slightly higher, and alkalinity was lower in undiked marshes than in diked marshes,
differences were small compared to levels known to cause major changes in biota (for
details, see Appendix C).
Invertebrate Community Parameters between Diked and Undiked Marshes

A total of 109,649 invertebrates were collected: 93,959 from diked marshes
(3,758/ sample, N=25) and 15,690 from undiked marshes (541/ sample, N=29) (Figure
2). Therefore the number of invertebrates/ sample (CPUE) was 7 times greater in diked
marshes than in undiked marshes. The total number of invertebrates per sample (p=0.03)
and species richness (p=0.05) were significantly different between diked and undiked
marshes (Table 1). These differences were consistent across all three plant zones with
diked marshes consistently having a higher total number of invertebrates per sample in
the three plant zones (26,121 to 40,459) compared to the total number of invertebrates/
sample three plant zones in undiked marshes (3,209 to 6,700) (Table 1). The number of
species collected from the three diked plant zones was also consistently and significantly

higher for the three

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plant zones in diked marshes (48 to 52 species) than for the three plant zones in
undiked marshes (33 to 36 species). There were no significant differences in total number
of invertebrates per sample (p=0.57) or species richness (p=0.88) among the three plant
zones in either the diked or undiked marshes (Table 1). Shannon diversity (H’) varied
from 1.04 to 1.16 in diked and undiked marshes, and differences were not significant
(p=0.78). Even though evenness (J ’) varied between 0.63 to 0.68 in diked marshes and
from 0.73 to 0.77 in undiked marshes, these apparently consistent differences between
diked and undiked marshes were not significant (p=0.20) (Table 1). Results were
consistent between the two diked marshes, the East and the West Management areas, and
between the two undiked marshes, Goose Bay/ Mud Lake and Little Muscamoot Bay, so
location had no significant effect on results (p=.49).

Comparison of Invertebrate Community Parameters in Diked and Undiked
Marshes.

A combined total of 144 taxa were collected from diked and undiked marshes
(Appendix A). A total of 113 taxa were collected from undiked marshes, and 121 taxa
were collected from diked marshes (Table 2). Ninety taxa were the same in both diked
and undiked marshes (Appendix B). There was a 77% similarity in invertebrate
communities between diked and undiked marshes based on Sorensen’s similarity index
(Table 2). Pairwise comparisons of invertebrate communities of the three plant zones in
diked marshes showed that they shared 73-78 taxa in common (80-82% similarity)
(Appendix B). In undiked marshes, the three plant zones shared 58-62 taxa in common
(72-76% similarity) (Appendix B). Comparisons of diked and undiked marshes by plant

zones showed that 58-67 taxa were shared in common (68-74% similarity) (Table 2,

15

Appendix B). Thus, the composition of invertebrate communities was similar overall as
well as on a plant zone basis based on Sorenson’s similarity index and the number of
species shared in common.

Of the 90 taxa shared in common between diked and undiked marshes, 61 were
statistically compared (Appendix B). These 61 either comprised >1% of relative catch,
occurred at >50% frequency, or were taxa known to be important in diets of foraging
waterfowl or wading birds (Appendix B). I also ran comparisons for the Class
Gastropoda, Amphipoda, and Oligochaeta and for six Insect orders: Odonata, Hemiptera,
Trichoptera, Lepidoptera, ColeOptera, and Diptera, between diked and undiked marshes
and between the three plant zones in diked and undiked marshes. Of the 61 taxa
compared (52 at the individual Operational taxon level, plus summaries for the Class
Gastropoda, Amphipoda, Oligochaeta and six insect Orders) based on total numbers of
each taxon per sample, 11 taxa were significantly greater (p< 0.05) and 11 taxa were
greater (p< 0.10) in diked marshes than in undiked marshes (Table 3). Eleven of 61 is
18% of all possible comparisons, more than 3 that would be expected by chance alone at
the p=0.05 level all 11 were significantly greater (p< 0.05) in diked marshes compared to
undiked marshes (Table 3).

More than 70% of the 7 fold average increase of 3,217 invertebrates/ sample
from undiked and diked marshes was contributed by 4 taxa; Caenis, a mayfly, Naididae,
a family of segmented worms, Gastropoda, a class of mollusks containing all snails, and
Hyallela azteca, an amphipod crustacean (Table 1, 3, and Figures 3-6).

An additional 9.3% of the 3,217 increase in invertebrates in diked marshes (300

invertebrates) was contributed by increases in flies (Diptera) with most of this increase

16

accounted for by increases in Chironomidae (non-biting midges) in the subfamilies,
Chironomini, Tanytarsini, and Tanypodinae (e.g., see Figure 7). The remaining 19-20%
of the increase was contributed by small but significant increases in Crangonyx, another
species of Amphipoda (p=0.09, Figure 8), water mites (Hydracarina)(p=0.01), leeches
(Hirudinea)(p=0.10), dragon and damselflies (Odonata)(p=0.02), especially
Coenagrionidae damselflies, pygmy backswimmers and other true bugs
(Hemiptera)(p=0.09), aquatic moths (Lepidoptera)(p=0.05), and aquatic beetles
(Coleoptera)(p=0.02) (Tables 1, 3).

H. azteca contributed more of the increase in diked marshes compared to undiked
marshes than any other taxon (Figure 3, 9, Table 3). The mean number of H. azteca
collected from diked marshes was 1,093/ sample compared to 31/ sample from undiked
marshes representing 1,062 (33%) of the mean total increase of 3,217 invertebrates/
sample in diked marshes compared to undiked marshes. The mean total number of H.
azteca/ sample was 35 times greater in diked marshes (p=0.02) than in undiked marshes
(Table 1, 3, Figure 3). The increase in H. azteca numbers in the bulrush (Schoenoplectus)
zone from a mean of 38/ sample (6% of the total catch) in undiked marshes to 1717/
sample (46% of total catch) in diked marshes is especially notable but increases in the
other two plant zones from 3-7% to 21% (from 11-42 mean total catch/ sample in
undiked marshes to 628-942/ sample in diked marshes were also impressive (Table 3,
Figures 3, 9). Two other genera of Amphipoda, Gammarus and Crangonyx, were also
present (Figure 9) with Crangonyx increasing its dominance along with H. azteca in
diked marshes compared to undiked marshes (Figure 8), while Gammarus decreased

from being the dominant amphipod in undiked marshes (a mean of 59/ sample

17

representing 10.9% of total catch) to complete absence in diked marshes (Figure 9).
Overall, mean total number of Amphipoda in diked marshes was 1239/ sample compared
to 101/ sample in undiked marshes. Thus, mean total increases in Amphipoda accounted
for 1138 invertebrates/ sample or 35% of the total increase in invertebrates/ sample.
Mean increases in diked marshes compared to undiked marshes in Caenis from 41
to 444/ sample, in Naididae from 114 to 399/ sample, and in GastrOpoda from 62 to 582/
sample combined accounted for 37.6% (1208) of the average increase of 3,217
invertebrates/ sample in diked marshes compared to undiked marshes (Figures 3-6). The
mayfly, Caenis, was 11 times greater in total numbers in diked marshes compared to
undiked marshes (p=0.06), and it was also more numerous in Phragmites zones
compared to T ypha or Schoenoplectus zones (p=0.08, Figures 4). Caenis was the only
mayfly collected from most marshes, so total numbers for Ephemeroptera and Caenis
were almost identical (Table 1). The segmented worm, Naididae, was 3.5 times greater
(p=0.06) in diked marshes than in undiked marshes (Figure 5). The total number of snails
(Gastropoda) per sample was 9 times greater in diked marshes compared to undiked
marshes (p=0.03) (Table 1, 3, Figure 6). Three individual snail taxa increased
significantly. Viviparidae snails increased from a mean of 11/ sample in undiked marshes
to 147/ sample in diked marshes (Table 3). Two other snails, Gyralus and Planorbella,
were also more numerous (p=0.06 and p=0.08, respectively) in diked marshes than in

undiked ones.

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The remaining increases in total invertebrates in diked marshes compared to
undiked marshes were contributed by relatively small increases in Hydracarina (aquatic
mites), Hirudinea (leeches), and 5 insect orders: Odonata, Hemiptera, Lepidoptera,
Diptera, and Coleoptera (Tables 1, 3). The mean number of water mites, Hydracarina,
per sample varied from 65 to 147/ sample in the plant zones in diked marshes compared
to 5-10/ plant zone in undiked marshes. Overall, water mites were 15 times greater in
diked marshes than in undiked marshes (p=0.01) (Table 3). There were four times more
leeches, Hirudinea, per sample in diked marshes than in undiked ones (p=0.10)

The mean total number of Odonata/ sample (dragon and damselflies) was 9 timer
greater in diked marshes (168/ sample) than in undiked marshes (18/ sample, p=0.02)
with increases in Coenagrionidae damselflies from 7/ sample to 53/ sample being part of
this increase. Mean Coenagrionidae/ sample was 7.5 times greater in diked marshes than
in undiked marshes (p=0.07). Odonata richness (p=0.02) was also significantly greater in
diked marshes (20 taxa) compared to undiked marshes (9 taxa).

Hemiptera increased from 42/ sample to 125/ sample, a 3 fold increase in diked
marshes compared to undiked marshes (Table 1, Table 3). The family of Hemiptera with
the greatest increase in total numbers per sample in diked marshes compared to undiked
marshes was the pygmy backswimmer family, Pleidae, from 3/ sample in undiked
marshes to 48/sample in diked marshes (p=0.05)(Table 1, Table 3). Interaction effects
between marsh type (diked and undiked) and vegetation type (Schoenoplectus, Typha, or
Phragmites) were significant for total numbers of Hemiptera (p=0.09) and for the

Hemipteran, Mesovelz'a (p=0.08). Mesovelia made up nearly 4% of total catch in undiked

23

marshes but was rare in diked marshes. Thus, this genus of Hemiptera actually responded
in the Opposite direction to the response of all Hemiptera combined and to Pleidae.

Lepidoptera total numbers increased from 1.2 to 206/ sample (p=0.05) in diked
marshes compared to undiked marshes (Table 1, Table 3). Lepidoptera diversity (H’)
(p=0.07) and evenness (J ’) (p=0.10) also slightly increased in diked marshes compared to
undiked ones. The only two taxa that were common enough to be tested statistically were
A centria and Paraponyx. Taxa richness was 6 in diked marshes and 7 in undiked ones
(Appendix B).

The mean total number of aquatic beetles, Coleoptera increased from 10/ sample in
undiked marshes to 53/ sample in diked marshes (p=0.02, Table 1, Table 3). Coleoptera
richness (18 species) also increased in diked marshes compared to undiked marshes (13
species) (p=0.06). Coleoptera diversity (H’)(p=0.10) and evenness (J ’) (p=0.07) showed
significant interaction effects between marsh type (diked and undiked) and plant zone
(Schoenoplectus, T ypha, or Phragmites). Coleoptera diversity (H’) was significantly
greater (p=0.03) in diked T ypha and Phragmites, compared to diked and undiked
Schoenoplectus, and undiked T ypha. Coleoptera evenness (J ’) was slightly greater
(p=0.06) in diked T ypha and Phragmites, compared to diked and undiked Schoenoplectus
and undiked T ypha.

The total number of flies, Diptera, was six times greater in diked marshes than in
undiked ones increasing from a mean of 66/ sample in undiked marshes to 366/ sample in
diked marshes (p=0.03, Table 1, Table 3). Diptera accounted for 300 or 9.3% of the total
increase of 3,217 invertebrates in diked marshes compared to undiked marshes. Three of

the Chironomidae midge subfamilies increase in diked marshes compared to undiked

24

ones (Table l). Chironomini (p=0.02), T anypodinae (p=0.02), and T anytarsini (p=0.04)
were significantly greater in diked marshes compared to undiked marshes (Table 1, Table
3). Combined mean numbers/ sample for the three midge subfamilies increased from 43/
sample in undiked marshes to 298/ sample in diked marshes, a 255 invertebrate increase
representing 7.9% of the total invertebrate increase in diked marshes compared to
undiked ones. The mean total number/ sample of Orthocladinae was not significantly
different between diked and undiked marshes (Table 1).

The total number of Caecia'otea, an Isopod, was three times greater in diked
marshes than in undiked ones (p=0.10). The total number of caddisflies, Trichoptera, also
increased by four fold in diked marshes compared to undiked ones (p=0.07).

The relative contribution to community composition as a mean percent of total
catch of common taxa are illustrated in Figure 9. Taxa that made up a greater percentage
of the community in diked marshes than in undiked marshes included the amphipod, H.
azteca. This illustrates that not only did their numbers increase 35 fold as discussed
above for H. azteca and all Amphipoda combined, but their dominance of the community
overall also increased substantially to 21-46% of total catch in diked vegetation zones
(p=0.02) compared to the 3-7% in undiked plant zones (Figures 3, 9, Table 3). In
contrast, the amphipod, Gammarus, was the most common amphipod in undiked marshes
contributing 10.9% of total catch/ sample on average (Table 5), but did not occur in diked
marshes (Figure 9) suggesting that it had been displaced from the community by H.
azteca and, perhaps to a lesser extent, by Crangonyx. In contrast, the relative contribution
of Naididae to community composition in diked marshes decreased compared to undiked

marshes (Table 5) even though its actual numbers increased 3.5 fold as discussed above.

25

Thus, its contribution to community composition decreased from undiked marshes (21%
of total catch) to diked marshes (12% of total catch) (Figure 9). The Order Hemiptera
(true bugs) made up a greater percentage of total catch in undiked marshes than in diked
marshes (Table 5). This was especially true of Mesovelia (Figure 9) which made up (4%)
of total catch in undiked marshes compared to (<1%) in diked marshes (Table 5, p=0.01).
However, the exception to this trend was Pleidae (Table 5, Figure 5) which increased in
total catch/ sample in diked marshes compared to undiked marshes (Figure 9). The
Gastropod, Physa, relative catch was greater (p=0.07) in diked T ypha (4%) and diked
Phragmites (3%) compared to diked Schoenoplectus (1%) (Table 4). The total number of
the Odonata, Enallagma, was statistically the same for diked and undiked marshes (Table
3). Tanytarsini relative catch slightly increased (p=0.09) in diked marshes and between
diked vegetation zones (p=0.08). These increases were in diked Typha (3 %) and
Phragmites (6%) zones compared to undiked Schoenoplectus (1%) and T ypha (1%)
zones. Caenis relative catch increased (p=0.08) in Phragmites dominated zones in diked
(16%) and undiked (13%) marshes (Table 4) compared to diked and undiked
Schoenoplectus (9% and 3%, respectively) and T ypha (6% and 3%, respectively) (Table
4). There were three times more Trichoptera, Oxyethira, in diked marshes but relative

catch was greater (p=0.08) in undiked marshes (Table 3, Table 5).

26

 

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31

Table 2. Sorensen Similarity Index with Number of similar taxa (% similarity) for

Diked and Undiked Marshes from Schoenoplectus, T ypha, and Phragmites zones.

 

 

 

 

 

 

 

 

 

 

 

# of Type # of Type # Shared
Taxa Taxa Taxa
(Similarity
%)
121 Diked 113 Undiked 90 (77%)
87 Diked 76 Undiked 58 (71%)
Schoenoplectus Schoenoplectus
101 Diked Typha 77 Undiked Typha 64 (72%)
9O Diked 86 Undiked 65 (74%)
Phragmites Phragmites

 

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34

Effects of Plant zonation on Invertebrate Community Parameters

Several taxa were commonly collected from all plant zones in diked and
undiked marshes (Figure 9). The dominant groups included the segmented worm,
Naididae, the Amphipods, Hyalella and Crangonyx, and the Ephemeropteran, Caenis
(Figure 9).

Maj or differences related to plant zone often involved difference between responses
in the Schoenoplectus (bulrush) zone compared to either the Typha (cattail) or
Phragmites (common reed) zones. For example, H. azteca made up 46% of total catch in
the diked Schoenoplectus zone but only 21 % in the other two plant zones in diked
marshes (Figure 9, Table 3). F our taxa were typically more abundant in the
Schoenoplectus zones of diked and undiked marshes than in the other two zones. Water
mites were frequently collected across all plant zones in diked and undiked marshes
(Table 6), but total number per sample showed a slightly significant (p=0.09) difference
between diked Schoenoplectus and diked and undiked T ypha, Phragmites, and undiked
Schoenoplectus (Table 3). The grass shrimp, Palaemonetes kadiakensis, comprised 0.5%
relative catch in diked marshes and 0.7% in undiked marshes (Table 4) and was collected
in 67% of the replicates in diked marshes (Table 6) and 37% of replicates in undiked
marshes. Four times more shrimp/ sample were collected in diked marshes than in
undiked marshes. While grass shrimp were collected more frequently in Schoenoplectus
zones, it was also collected in T ypha (30% of replicates in diked marshes, 4% in undiked
marshes) and Phragmites (26% of replicates in diked marshes, 3% in undiked marshes)
replicates. There were ten times more Corixidae, Hemiptera, which were collected in

71% of diked Schoenoplectus replicates compared to 30% of undiked Schoenoplectus

3S

replicates (Table 6). Corixidae made up 2.2% of the diked Schoenoplectus zone and was
<0.5% in the diked T ypha and diked Phragmites zone (Table 4). The burrowing water
beetle, Hydrocanthus, comprised 0.8% relative catch in diked marshes and 1.1% in
undiked marshes (Table 4), but less than 1% total number per sample in both diked and
undiked marshes (Table 3). There were eight times more Hydrocanthus in diked marshes
and it was collected in 62% of diked replicates, compared to 17% of undiked replicates
(Table 3). Hydrocanthus was collected in less than 50% of diked and undiked T ypha
(41% and 15% respectively) and Phragmites (37% and 32% re5pectively) replicates.

In the T ypha zone, differences occurred between the taxa in diked and undiked
marshes. In undiked marshes, the damselfly, Ischnura, the fishfly, Chaulioa’es, and the
soldierfly Family, Stratiomyidae, each comprised 1% total number per sample of the
invertebrate community but less than 1% of the diked community (Table 4). There were
four times the number of Odonata, Ischnura, three times Chauliodes, and twice the
number of Stratiomyidae in diked marshes compared to undiked wetlands. Ischrzura and
Chauliodes were infrequently collected in undiked replicates (3-16% and 13-26%
respectively) and diked replicates (1 1—48% and 19-43% respectively). Stratiomyidae was
similarly infrequently collected in undiked replicates (19-33%) but was collected in 70%
of the diked Typha replicates compared to diked Schoenoplectus (24%) and Phragmites
(26%).

In diked T ypha marshes, the snail, Gyraulus crista, the caddisfly, Polycentropus,
and the moth, Parapoynx, each comprised 1% total number of the invertebrate
community but less than 1% in undiked marshes. G. crista was not found in undiked

marshes but was collected in 14% of Schoenoplectus, 52% of T ypha, and 56% of

36

Phragmites diked replicates. There were 57 times more Polycentropus and 15 times more
Parapoynx in diked marshes compared to undiked marshes. Polycentropus and
Parapoynx were rarely collected in undiked replicates (3 -7% and 3-19%, respectively),
but in diked replicates they were frequently collected (48-76% and 52-63%, respectively)
(Table 6).

In the Phragmites zone, differences also occurred between taxa of diked and
undiked marshes. In undiked Phragmites, the water-striders, Gerridae, the velvet water
bug, Hebridae, the minute moss beetle, Hydraenidae, and dixid midges, Dixidae, each
comprised 1% total number of the invertebrate community. There were eight times the
number of Hebridae, and ten times the number of Dixidae in undiked marshes compared
to diked marshes but there was twice the number of Hydraenidae in diked marshes
compared to undiked marshes. The number of Genidae was the same for diked and
undiked wetlands. Generally, all four of these taxa were rarely collected (<25%) in either
diked or undiked replicates. The only exception was Hydraenidae which was collected in
41% of diked Phragmites replicates.

In diked Phragmites, total number of the limpet, Ancylidae, was seven times
greater, the immature dragonfly, Libellulidae was 374 times greater, and the caddisfly,
Leptocerus was 131 times greater, compared to undiked marshes. Each of these taxa
comprised 1% of the diked invertebrate community but <1% in undiked marsh
community. Ancylidae was collected in 32-3 7% of undiked replicates and increased to
37-81% of diked replicates (Table 6). Immature Libellulidae were rarely collected in
undiked marshes (0-4%), but were frequently collected in diked replicates (76-89%).

Immature Leptoceridae and Leptocerus were rarely collected in undiked (0-6% and 0-7%,

37

(0-6% and 0-7%, respectively) replicates and generally were infrequent in diked (0-

33% and 4-22%, respectively) replicates.

Table 4. Mean Invertebrate Relative Catch >0.5% (:tStandard Error) in Diked

and Undiked Marshes.
Taxa
Oligochaeta Naididae
Tubificidae
Mollusca Sphaeriidae
GastrOpoda Viviparidae
Lymnaeidae
Physidae
Planorbidae
Arachnida Hydracarina
Amphipoda Crangonyctidae
Gammaridae
Talitridae
Isopoda Asellidae
Ephemeroptera Caenis
Odonata Coenagrionidae
Libellulidae
Hemiptera Belostomatidae
Mesovelidae
Nepidae
Pleidae
Homoptera
Trichoptera Hydroptilidae
Leptoceridae
Diptera Ceratopogonidae
Chironomidae

*** Significant at (p<0.01)
** Significant at (p<0.05)
* Significant at (p<0.10)

Stagm'cola
Physa
Gyraulus
Planorbella

Crangonyx
Gammarus
Hyalella
Caecidotea
Caenis
1mm.
Enallagma
1mm.
Belostoma
Mesovelia
Ranatra

Oxyethira
Cercalea

C hironomini
T anytarsim’
Orthocladinae
T anypodz'nae

38

Undiked Diked
213212.79 11.7d:1.52
1.43:0.69
1.63:1.05 2.2:t0.47
2.5:t0.96 3.15:0.82
1.5:t0.58 O.6:l:0.33
1.9i0.36 2.8i0.51
3.0:I:O.44 5.0i1.07
0.7:1:0.23 1.610.30
l.8i0.30 3.0i0.36
2.7:t0.61 5.3il.78
10.9:t2.06
5.55:1.51 25.1**:l:2.79
1.8:t0.59 1.4:t0.40
6.35:1.76 10.3:t1.73
1.2:tO.27 1.110.21
1.8**i0.41
1.6i0.3l
1.4:t0.29
3.8***¢O.87
l.l:l:0.21
O.5:1:0.24 2.0i0.33
1.010.31
l.1*iO.32 0.73:0.23
l.3:t0.35
4.2i1.00 1.1:t0.23
2.5:le.43 3.2:tO.45
l.0i0.27 3.9*=t0.89
1.710.39
1.6i0.21 2.0i0.36

Functional Feeding Groups

Gatherer-collectors comprised approximately 60% of invertebrates collected in
diked and undiked marshes while predators made up approximately 20% and scrapers
approximately 10% (Figure 9). Comparisons between diked and undiked vegetation
zones showed similar trends with gatherer-collectors (49 to 70% in diked vegetation
zones and 52-62% in undiked vegetation zones) being the most dominant functional
group (Figure 9). Gatherer—collectors, which feed mainly on decomposing fine particulate
organic material (Merritt and Cummins 1996), have been reported to dominate coastal
marshes that are vegetated and accumulate detritus (Merritt et al. 2002) which generally
characterize the diked and undiked marshes I was sampling.

Except for diked Typha and Phragmites zones, in which scrapers made up a greater
percentage (25% and 16% respectively) than predators (15% and 13% respectively)
(Figure 9), predators were more abundant than scrapers between diked and undiked
vegetation zones (Figure 9).

Functional Habitat Groups

There were only minor differences in the percentages of habitat groups between
diked and undiked marshes (Figure 10). In undiked marshes, burrowers comprised 28%
of the invertebrate community and dominated the Schoenoplectus zone (35%) (Figure
10). In diked wetlands, swimmers comprised the greatest percentage of invertebrates
(40%) and also dominated the Schoenoplectus zone (60%) (Figure 10). Climbers made up

a greater percentage of the undiked community (11%) compared to the diked community

(4%) (Figure 10).

39

Sprawlers increased in the Phragmites zones of diked and undiked marshes (24%
and 26%) compared to the diked and undiked Schoenoplectus (13% and 14%,
respectively) and T ypha zones (15% and 13%, respectively) (Figure 10). This difference
reflects the fact that Caenis contributed a substantial portion of the invertebrate

community of Phragmites zones (Table 1, Table 3, and Figure 8).

40

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Invertebrate Frequency

Naididae was the most frequently observed invertebrate (>90%) collected in diked
and undiked marshes (Table 6). In undiked marshes, Amphipoda was the second most
frequently found taxa but Gammarus was the only Amphipod to be frequently caught in
all three vegetation zones (77-89%) (Table 6). Hydracarina was also frequently found in
all three vegetation zones (67-70%). Four Gastropods were frequently found in the
Schoenoplectus zone while three were found in the Phragmites zone and only one
(Gyraulus) was found in the Typha zone. There were five Dipterans that were found in
Phragmites, four in T ypha, and three in Schoenoplectus (Table 6). Mesovelia was only
frequent in Schoenoplectus (73%) and T ypha (81%) zones. Caenis was only frequent in
Typha (52%) and Phragmites (77%) zones. Schoenoplectus was unique from the other
zones in that immature Coenagrionidae (53%), Enallagma (70%), and Oxyethira (50%)
were only caught in that zone at a frequency >50% (Table 6). Typha had three unique
taxa: Crangonyx (59%), Caecidotea (56%), and Belostoma (59%) (Table 6). Phragmites
had two unique taxa: Ranatra (68%) and Homoptera (58%) (Table 6).

In diked marshes, Gyraulus (95-100%), Hyalella (100%), Caenis (100%),
Chironomidae pupae (100%), and Tanypodinae (90-100%) were all found at >90%
frequency (Table 6). Hydracarina was found at 100% of replicates collected from
Schoenoplectus and Phragmites, but only at 89% in T ypha. Hirudinea was frequently
found in all three vegetations but was most frequently found in Schoenoplectus (81%).
Parapoynx was also frequently found in all three zones (52-63%). Seven Gastropods

were frequently found in Schoenoplectus and Phragmites marshes and five were found in

Typha.

43

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Ancylidae and Viviparidae were found in Schoenoplectus (52%) and Phragmites
(81%) zones and Gyraulus crista was found in Typha (52%) and Phragmites (56%)
zones. Amphipods were found in all three zones but Crangonyx was only frequent in
Schoenoplectus (67%) and Typha (93%) zones. There were three Odonata frequently
caught in Schoerwplectus and Phragmites zones but only two in Typha. Most Hemiptera
that were frequently caught were from the SchoenOpIectus zone. Three TrichOptera were
frequent in Schoenoplectus and Phragmites zones but only Setodes (52%) was in Typha.
Each zone had five Dipterans frequently found. Schoenoplectus had six unique taxa:
Stagm'cola (67%), Palaemonetes (67%), Lirceus (57%), Enallagma (67%), Mesovelia
(76%), Veliidae (52%), and Hydrocanthus (62%) (Table 6). Typha had two unique taxa:
Chironomini (59%) and Stratiomyidae (70%) (Table 6). Phragmites had two unique taxa:
Corduliidae (56%) and Orthocladinae (52%) (Table 6).

DISCUSSION

My hypothesis that invertebrate community species composition, total catch/
sample, richness, and evenness would differ significantly between diked and undiked
coastal marshes was partially supported. The total number of invertebrates per sample
and taxa richness significantly increased in diked marshes compared to undiked marshes.
The number of invertebrate/ sample was seven times higher in diked marshes than in
undiked marshes increasing from a mean of 541/ sample in undiked marshes to 3,748/
sample in diked marshes. Eighty percent of this unexpectedly large increase was the
result of increases in five taxa that are known to be important in waterfowl and wading
bird diets. They included Amphipoda, especially H. azteca, Naididae worms, Caenis

mayflies, snails (Gastropoda), and non-biting midges (Chironomidae). Marshes have

46

traditionally been diked for waterfowl management in Great Lakes coastal marshes, and
my findings suggest that diking is effective in producing more food for breeding
waterfowl, especially when accompanied by maintenance of channels for hunter access. I
sampled near the edge of each of the three plant zones, so invertebrates were likely a
combination of taxa characteristic of the emergent zone and the adjacent open water
channel dominated by submergent, floating and floating-leafed plants. Each area sampled
was located in habitat where waterfowl or other water birds had been observed. These
results suggest that waterfowl and wading birds feeding in the outer edge of the three
plant zones have substantially greater access to invertebrate food resources in diked
marshes than they do in undiked marshes.

Taxa richness increased from 33-36 taxa in undiked marshes to 48—52 taxa in diked
marshes (Table 1). There were no significant differences in invertebrate diversity (H’) or
evenness (J ’) between diked and undiked marshes. Invertebrate communities in diked and
undiked marshes shared 9O taxa in common out of a total of 144 taxa collected from Lake
St. Clair marshes. Sorenson’s percent similarity between diked and undiked communities
and among communities in the three dominant plant zones was >70% for most
comparisons. Thus, changes in community composition between diked and undiked
marshes generally involved less than 30% of the taxa present in both. Of particular note
was the substantial increase in dominance by H. azteca in diked marshes and its apparent
displacement of Gammarus as the dominant amphipod in diked marshes compared to
undiked marshes.

Dominant taxa were similar between diked and undiked marshes at the family or

Order level with minimal differences among the three dominant plant zones present

47

(Schoenoplectus, T ypha, and Phragmites). Dominant taxa included segmented worms,
Naididae, side-swimmers or scuds, Hyalella and Crangonyx, the mayfly, Caenis, and
snails, Gastropoda (Figure 9). These dominant groups are consistent with other
researcher’s findings for Lake St. Clair and the St. Clair River invertebrate communities
(Davis et al. 1991, Ciborowski and Corkum 1988, French 111 1988, Herdendorf et al.
1986). Additionally, other researchers have described these taxa as being dominant in
Lake Ontario (Barton 1986), Lake Erie (De Szalay and Cassidy 2001, Herdendorf 1987)
and Lake Huron coastal wetlands (Burton et al. 2002, Stricker et al. 2001, Barton and
Griffiths 1984).

My findings differ from results found by McLaughlin and Harris (1990) for
marshes in Green Bay, Wisconsin. They did not find significant differences in total
number of invertebrates in diked marshes compared to undiked marshes but suggested
that there were more invertebrates in diked marshes than undiked marshes. A possible
reason that they failed to find significant differences was that they only sampled
emerging insects. This would have excluded Naididae and Amphipoda, which dominated
the invertebrate community in diked and undiked marshes in Lake St. Clair marshes
(Figure 9).

My second hypothesis was that the invertebrate parameters listed above would be
affected by plant zonation in diked and undiked marshes. I did not find significant
differences in total number per sample, taxa richness, diversity, or evenness among plant
zones in diked or undiked marshes. There were significant differences between the
Coleoptera community of diked vegetation zones, and marginally significant differences

in the Hemiptera community. Plant zone was marginally significant for seven taxa in

48

diked marshes, and was marginally significant for the mayfly, Caenis, in undiked
marshes.

In other studies of Great Lake coastal marshes, vegetation type was correlated with
the type of macroinvertebrate community present (Burton et al. 2004, 2002, French III
1988). McLaughlin and Harris (1990) and De Szalay and Cassidy (2001), showed that the
largest numbers of invertebrates were found in sparse emergent zones within diked
marshes but neither study found a significant difference between emergent vegetation
zones and open water zones in diked marshes. Thus, my results are consistent with their
studies.

Additionally, Fell et al. (2003) and Kulesza et al (2008) failed to find significant
differences between the macroinvertebrate communities in T ypha and Phragmites
dominated marshes. I detected marginally significant differences between Crangonyx
relative catch, Caenis total number and Caenis relative catch between Phragmites
dominated zones compared to T ypha, and Schoenoplectus zones but generally the
invertebrate community was the most similar between T ypha and Phragmites.

Like De Szalay and Cassidy (2001), the invertebrate community was dominated by
invertebrates classified as gatherer-collectors (60%) which included the Oligochaetes, the
Amphipods, and mayflies. Scrapers and Predators were abundant in diked and undiked
marshes (>10%) and were mainly comprised of snails and mostly Odonates,
Hemipterans, ceratopogonids, and chironomids. While De Szalay and Cassidy (2001)

failed to collect any Filterers or Shredders, I did find a few but they made up <5% of the

invertebrate community.

49

I documented differences in the three plant zones common to diked and undiked
marshes in order to document changes in the potential prey base of avian fauna of diked
and undiked Great Lake coastal marshes. Primarily, marsh birds eat immature and adult
insects, snails, and crustaceans (Mazak et al. 1997, Kaminski and Prince 1981, Swanson
et al. 1974, Krull 1970). Each avian species selectively forages for particular
invertebrates, and favors intermediate to large—sized invertebrate families (Mazak et al.
1997, Kaminski and Prince 1981, Swanson et al. 1979, Swanson et al. 1974). I frequently
(>50% replicates) caught more large organisms, such as Lepidoptera and Odonata, in
diked marshes than in undiked marshes (Table 6). In fact, there were 13 times more
Lepidoptera and 9 times more Odonates in diked marshes (Table 3). The Gastropods,
Viviparidae, Gyraulus, and Planorbella significantly increased in diked marshes and
there were between 8-13 times more in diked marshes. The largest significant increase in
diked marshes compared to undiked marshes was the very large 35 fold increase in the
amphipod crustaceans, Hyallela and Crangonyx. Amphipods are among the important
prey for waterfowl and fish in the Midwest (Anteau and Afton 2008) and are known to
reach very high densities in submersed aquatic vegetation. Submersed aquatic vegetation
was common in the hunter access channels adjacent to the emergent zones that I sampled
in the diked marshes.

Krull (1970) suggested that the vegetation zone-invertebrate interaction is important
for foraging avian species. He showed that plants that were poor waterfowl food,
typically harbored more invertebrates and that these plants would be indirectly important
for waterfowl. Examples of invertebrates which showed changes between plant zone and

which may be important to birds in diked and undiked marshes include: the grass shrimp

50

in Schoenoplectus zones of diked and undiked (Table 3, Table 4) marshes: the moth,
Parapoynx in diked (Table 3, Table 4), and damselfly, Ischnura in undiked Typha zones
(Table 3, Table 4); and the mayfly, Caenis, which is found in the highest relative catch in
the Phragmites zones in diked and undiked marshes (Table 3, Table 4).

Just as McLaughlin and Harris (1990) suggested, diked marshes would seem to be a
preferred habitat for foraging marsh birds because of the significant increase in aquatic
invertebrates. Preliminary examination of data from bird surveys at randomly selected
open water areas at St. Clair Flats indicate higher densities of Canada goose (Branta
canadensis), wood duck (Aix sponsa), and black tern (Chlidonias niger) in diked
compared to undiked marshes; however, black terns were only observed nesting in
undiked marshes and densities varied by site and year (M. Monfils pers. comm). In
undiked coastal marshes, mallard (Anas platyrhynchos), American coot (F ulica
americana), pied-billed grebe (Podilymbus podiceps), and F orster’s tern (Sternaforsteri)
were recorded at higher overall densities compared to diked areas, although densities also
varied by site and year (M. Monfils pers. comm.) Many of the above avian species eat
large amounts of invertebrates during the breeding season (Herdendorf et al. 1986,
Kaminski and Prince 1981, Krull 1970)

Conclusion

The St. Clair River delta marshes are highly productive Great Lakes coastal
marshes that exhibit high habitat and species diversity (Albert 2003, French III 1988,
Herdendorf et al. 1986). Some notable examples of threatened and endangered species
include: the king rail (Rallus elegans), the spotted turtle (Clemmys guttata), and the

eastern fox snake (Elaphe gloydi) (personal observations). These marshes also support

51

great numbers of avian fauna that utilize these marshes as important resting and/or
breeding areas (Prince et al. 1992, Herdendorf et al. 1986, personal observations). While
there is extensive literature on the feeding ecology of waterfowl (Mazak et al. 1997,
Prince et al. 1992, Kaminski and Prince 1981, Swanson et al. 1979, Swanson et al. 1974),
few studies have looked at the invertebrate community within diked Great Lakes coastal
marshes which are managed for waterfowl production (De Szalay and Cassidy 2001,
McLaughlin and Harris 1990, Herdendorf et al. 1986)

Studies have demonstrated that diking coastal marshes leads to changes in the
aquatic invertebrate, fish and plant communities (Herrick and Wolf 2005, Thiet 2002,
Jude and Pappas 1992, McLaughlin and Harris 1990). These studies have shown mixed
results as to whether these diked marshes are beneficial or harmful. In general, dikes
cutoff water fluctuations that naturally occur in coastal marshes, harbor greater number of
invasive plants, and are generally nutrient enriched (Herrick and Wolf 2005, Thiet 2002,
McLaughlin and Harris 1990, Herdendorf et al. 1986).

While diked marshes were more productive for the overall invertebrate community, _
it should not be concluded that diking coastal marshes is beneficial. In fact, diked
marshes harbored more invertebrates that are typically collected in inland marshes, such
as mosquitoes which were collected in 10-19% of diked replicates compared to 0-4% of
undiked replicates. Additionally, there appeared to be taxa that were sensitive to diked
marshes, such as the marsh treader, Mesovelia, which total number typically was greater
in undiked marshes, and the damselfly, Enallagma, which uncharacteristically, of the

other Odonates, did not increase in total number in diked marshes. The amphipod,

52

Gammarus, was a dominant invertebrate in undiked marshes but was absent from diked
marshes.

I did not find significant effects caused by vegetation zone but I did find seven taxa
in diked marshes and one taxon in undiked marshes that were marginally significant
between plant zones. This was not surprising due to the fact that I limited sampling to the
edges of vegetation zones where marsh birds predominately feed. In other coastal
marshes, plant zone and water level fluctuations are important covarying factors that
structures invertebrate communities (Burton et al. 2004, 2002, Stricker et al. 2003,
Merritt et al. 2002, Cardinale et al. 1998). Future studies of the invertebrate community
of the St. Clair deltaic coastal marshes should focus on sampling areas that are firrther
into vegetation zones so as to exclude edge effects if the goal is to describe differences
among plant zones. I was more interested in documenting the differences in habitat use at
the edge of the three plant zones, since this is where most aquatic birds concentrate their
feeding, and in documenting differences between diked and undiked marshes.

Phragmites appears to be expanding its dominance of coastal wetland plant
communities throughout the Great Lakes region and may potentially cause significant
changes to invertebrate and vertebrate communities in other Great Lake coastal marshes.
While my study results may be useful for trying to determine the effects of the
Phragmites spread, it should be used with caution. By sampling the edge of Phragmites
dominated marshes, I sampled areas that were potentially the newest growth in which the
invertebrate community would not have had enough time to redistribute itself. Also,
invertebrates from the adjacent channels were likely included in the areas that I sampled.

To truly test the effects that the invasion of Phragmites has on marsh invertebrate

53

communities, samples would have to be collected in mature stands and far enough into

the vegetation stand to exclude edge effects.

54

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67

Appendix D. Mean Hemiptera Shannon’s Diversity (H ’), Taxa Richness, Evenness

(J ’) for Diked and Undiked Marshes, from Schoenoplectus, T ypha, and Phragmites

 

 

 

 

 

 

 

 

 

Zones.

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J ’)

Undiked 0.60i0.03 5.97:t0.36 O.8ld:0.02

Schoenoplectus O.57:b0.04 S .4:t0.65 0.81i0.03

Typha 0.601007 6.33zt0.69 0.77i0.04

Phragmites 0.65i0.04 6.20i0.55 0.841002

Dike 0.51i0.03 5.56i0.39 0.72i0.04

Schoenoplectus 0.50rt0.06 629320.84 066220.08

Typha 0.56zt0.05 5.11i0.45 0.83:t0.05

Phragmites 04610.06 5.44i0.75 0.662t0.05

 

 

 

 

 

 

68

 

Appendix E. Mean Odonata Shannon’s Diversity (H ’), Taxa Richness, and

Evenness (J ’) for Diked and Undiked from Schoenoplectus, T ypha, and Phragmites

 

 

 

 

 

 

 

 

 

Zones.

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J')

Undiked 0.27i0.04 23110.24 0.62:0.07

Schoenoplectus 0.29zt0.06 2.602t0.48 0.67dz0. 12

Typha 0.26:0.07 2.11i0.42 0.61t0.15

Phragmites 02610.06 2.20:0.” 0.571013

Diked O.57i0.04 6.28i0.47 0.76:1:002

Schoenoplectus 0.52:0.06 5.71:0.84 0.73:0.05

Typha 0.64:t0.06 6.78:1:0.72 0.81:0.03

Phragmites 0.551006 6.230.912 0.74:0.05

 

 

 

 

 

 

69

 

Appendix F. Mean Trichoptera Shannon’s Diversity (H ’), Taxa Richness,

Evenness (J ’) for Diked and Undiked Marshes from Schoenoplectus, T ypha, and

 

 

 

 

 

 

 

 

 

Phragmites Zones.

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J ’)

Undiked 0.34i0.04 3.171041 0.61i0.07

Schoenoplectus 0.3 li0.08 3.70i0.9l 0.55zt0.09

Typha 0.3]:t0.10 2.44zt0.82 0.57-J:0.l9

Phragmites 0.38i0.06 3.30:t0.60 0.72zt0.09

Diked 0.46i0.03 4.28:0.34 0.77:0.04

Schoenoplectus 0.481006 4.57i0.72 07710.06

Typha 0.4lzt0.06 3.56i0.58 0.76:0.10

Phragmites 0.50i0.05 4.78i0.49 0.77:0.05

 

 

 

 

 

 

70

 

Appendix G. Mean Lepidoptera Shannon’s Diversity (H ’), Taxa Richness,

Evenness (J ’) for Diked and Undiked Marshes from Schoenoplectus, T ypha, and

 

 

 

 

 

 

 

 

 

Phragmites Zones.

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J ’)

Undiked 0.03i0.02 0.59:1:0. 13 0.10i0.06

Schoenoplectus 0.03:0.03 0.50i0.22 0.10i0.10

Typha 0.03i0.03 0.67:0.24 0.1 13:01 1

Phragmz'tes 0.03:t0.03 0.60i0.22 0.09i0.09

Diked 01810.03 18410.19 0.46i0.08

Schoenoplectus 0.23:1:006 1.86:1:0.4O 0.63:1:0. 17

Typha 0.15:1:0.05 1.89:1:035 0.39:t0. l3

Phragmites 0.1755005 1.78i0.28 0.39:1:0. 14

 

 

 

 

 

 

71

 

Appendix H. Mean Coleoptera Shannon’s Diversity (H ’), Taxa Richness,

Evenness (J ’) for Diked and Undiked Marshes from Schoenoplectus, T ypha, and

 

 

 

 

 

 

 

 

 

Phragmites Zones.

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J ')

Undiked 0.3710.04 3.1010.32 06710.07

Schoenoplectus 03110.07 27010.45 06610.12

Typha 02910.10 23310.62 05210.16

Phragmites 05110.05 42010.44 08310.04

Diked 0.5710.07 6.4810.91 0.7010.06

Schoenoplectus 0.2310.12 3.1411.14 0.3210.14

Typha 07110.10 8.5612.03 0.8610.02

Phragmites 0.711006 7.001067 0.841004

 

 

 

 

 

 

72

 

Appendix I. Mean Gastropoda Shannon’s Diversity (H ’), Taxa Richness, and

Evenness (J ’) for Diked and Undiked Marsh from Schoenoplectus, T ypha, and

Phragmites Zones.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Marsh Type Vegetation Zone Diversity (H ’) Richness Evenness (J ’)
Undiked 05210.03 5.101036 0.751003
Schoenoplectus 0.561003 5.801055 0.781004
Typha 04510.08 4.221074 0.691009
Phragmites 05410.04 5 .201051 07710.02
Diked 06110.03 7.281038 0.721002
Schoenoplectus 0.661006 75710.92 07710.05
Typha 05610.05 6.891063 0.681005
Phragmites 0.631003 7.441050 07310.02

 

73

 

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