The Great Lakes Center of Buffalo State College, in collaboration with U.S. Environmental Protection Agency’s Great Lakes Biology Monitoring Program and Office of Research and Development-Great Lakes Toxicology and Ecology Division, has developed a new method for rapid assessment of dreissenid (zebra and quagga) mussel populations in lakes.
The method uses a Benthic Imaging System to estimate population size of these ecosystem invaders in near-real time. The BIS consists of Go-Pro cameras and lights mounted to a steel frame that is lowered to the lakebed from a ship. The resulting bottom images are analyzed via imaging software to estimate mussel density and percent coverage by mussels. The BIS substantially reduces the time required to map distributions of dreissenid mussels across large spatial scales compared to traditional sediment collection methods.
During the first lake-wide BIS survey of Lake Erie in 2019, the team completed maps of dreissena abundance and coverage within 12 hours after the final station was sampled. The BIS was used in tandem with traditional sediment grabs, as both methods have their own unique strengths.
Sediment grab samples produce information on species composition, size-frequency distribution, and density data necessary to calibrate and verify the results of BIS assessment. Sediment grabs also remain reliable options for sampling areas with high turbidity and macrophyte, or aquatic plant, coverage, conditions that limit image quality.
Since their introduction, dreissenid mussels have become a major driver of many ecological processes in the Great Lakes. Generating updated maps of their spatial distributions and population structure within the lakes is therefore of particular interest to scientists and managers.
This rapid dreissenid assessment method was piloted in Lake Erie aboard the EPA R/V Lake Guardian, as part of the 2019 Cooperative Science and Monitoring Initiative lakewide benthic survey with NOAA’s Great Lakes Environmental Research Laboratory as a partner. The BIS assessment, coupled with sediment Ponar grabs, revealed a decline in dreissenid mussel population density and biomass in the Lake Erie’s western basin compared to the previous lakewide CSMI survey in 2014. Researchers hypothesize that periodic die-offs of adult dreissenid mussels occur in the western basin during episodic hypoxia events and winter storms, resulting in a population dominated by small juvenile mussels that settle after disturbance subsides.
The resulting research paper Rapid assessment of Dreissena population in Lake Erie using underwater videography is published online with @SpringerNature in Hydrobiologia. This project and the EPA Great Lakes Biology Monitoring Program are supported by the Great Lakes Restoration Initiative.