Lake type and connectivity predict zebra mussel (dreissena polymorpha) presence

Studies that differentiate between lake type or origin, i.e., natural lakes and reservoirs, or that focus solely on reservoirs are rare, especially at broad scales. These facts lead to reservoirs being less well understood compared to natural lakes. It is known that adding dams/impoundments alters the flow regime of the original water body and changes surface water connectivity. However, the impact of these alterations on invasive species dispersal is widely unknown. Reservoirs are also thought to have higher levels of human disturbance, which can provide opportunities for non-native species such as the zebra mussel (Dreissena polymorpha) to invade and establish. Surface water connections allow zebra mussel larvae to flow from one waterbody to another. Additionally, trailering of recreational boats among lakes can promote overland dispersal of zebra mussels through live wells and boating equipment. Although such connectivity promotes zebra mussel spread, we do not yet know how zebra mussels vary according to lake type nor the relative roles of surface and human connectivity and lake type. Taking a data-intensive approach at the macroscale, we ask: Are zebra mussels more common in reservoirs than in natural lakes? How does surface water and human connectivity influence the presence of zebra mussels in reservoirs and natural lakes? To answer these questions, we used 907 lakes within a 17-U.S. state extent and data from a variety of sources. Water quality, surface water connectivity, and human disturbance data were from the LAke multi-scaled GeOSpatial and temporal (LAGOS) database, public lake access sites were from the United States Geological Survey (USGS), and zebra mussel presence data were from the USGS Nonindigenous Aquatic Species database. We characterized surface water connectivity using six unique lake connectivity classes. We characterized human connectivity two ways: watershed road densities measured in meters per hectare and, for a 3-state subset of the study extent, the presence of public access sites on lakes. We characterized surface water connectivity using a lake connectivity classification based on lake and stream inflow(s)/outflow(s). Using logistic multiple regressions and controlling for region and lake chlorophyll a concentrations, we found that a higher proportion of reservoirs have zebra mussels compared to natural lakes for the 17-state extent. At this same spatial extent, we found that more highly connected lakes, both by humans and surface waters, were more likely to have zebra mussels present, regardless of lake type. Finally, at the 3-state extent, lakes with a public access site were more likely to have zebra mussels than those without, regardless of lake type. We conclude that not all 'lakes' are equally likely to have zebra mussels present and that both surface water and human connectivity are important predictors of zebra mussel presence. This study improves the understanding of how natural lakes and reservoirs differ and the extent to which reservoirs disproportionately harbor the invasive zebra mussel, which can improve management and prevention. For example, these results suggest that legislation and management focused on uninvaded reservoirs that are highly connected may help slow the spread of this invasive species.