Using Field Experimentation to Assess Recovery of the Benthic Macroinvertebrate Community

Using Field Experimentation to Assess Recovery of the Benthic Macroinvertebrate Community in Onondaga Lake, NY

Brandeis L. Brown

M.S. Candidate Ecology

SUNYCollege of Environmental Science and Forestry

Final Report

Edna Bailey Sussman Foundation

December 2009

Rationale

OnondagaLakeis a highly disturbed urban system (Syracuse, NY)that has experienced more than a century of industrial and municipal pollution. A large scale multimillion dollar remediation is currently underway and has recently resulted in significant improvements in surface water quality. These initial water quality improvements have led to positive changes in aquatic communities, including plants and fish, but have had limited influence on the recovery of the benthic macroinvertebrate community. Recovery of the benthic macroinvertebrate community is limited by the contaminated sediments that still exist in the lake and may be limited by dispersal from the similarly impaired tributaries. Future sediment remediation is planned for this lake, but it is unclear whether this will allow for the natural recovery of the benthic macroinvertebrate community or if further management actions are needed.

Summary of Proposed Work

The overall purpose of this research was to investigate the ability of the benthic macroinveretebrate community to recolonize the lake after remediation is complete. We conducted a field experiment in 2008 using artificial substrates to eliminate the poor sediment quality as a factor in recovery and assess natural dispersal to the lake. We collected these clean substrates at five sites in OnondagaLake and a reference lake (OtiscoLake)over a 14 month period. Macroinvertebrates were sorted and identified to family level. The objective of this internship was to work with the New York State Department of Environmental Conservation (NYDEC) Stream Biomonitoring Unit (SBU) to further analyze the colonists on these artificial substrates. Specifically we aimed to analyze (1) specimens to a higher taxonomic resolution, (2) use this information to compare macroinvertebrate dispersal to OnondagaLake vs. OtiscoLake and (3) determine which macroinvertebrate bioassessment metrics differed between OnondagaLake and the reference lake in order to suggest useful parameters infuture monitoring protocols. In addition, the NYDEC is working to implement a new lakebioassessment protocol that will be used to assess and monitor the level of impairment of freshwater lakes in New YorkState. I planned to use preliminary data collected by the NYDEC SBU in the development of this new metric to incorporate into my analyses as another goal of this internship.

Narrative of Research

The first goal of this internship was to further identify certain aquatic insect groups that were of special interest to a higher taxonomic resolution (genus and species) with the verification of specially trained taxonomists. This was made possible by working with Alexander J. Smith and other taxonomists at the NYDEC SBU. This new taxonomic information enhanced many aspects of this project. Not only did it allow accurate assessment of dispersal to these lakes but also allowed incorporation of species-specific pollution sensitivity values into theinterpretationof the results of this study. In addition, with the help of further identification, I was able to monitor the colonization of a new exotic species to OnondagaLake, the quagga mussel (Dreissena bugensis). This study revealed that quagga mussels were not found in the less disturbed OtiscoLake, supporting the classic ecological hypothesis that disturbed ecosystems are more prone to invasion by exotic species.

Next, I analyzed macroinvertebrate dispersal to OnondagaLake to determine the potential for natural recovery of the community. I did not find any new taxa dispersing to the lake that were not found recently in macroinvertebrate surveys. Next, I determined that there were 24 taxa found dispersing to substrates in OtiscoLake and that the major difference between dispersers to the lakes include two families of mayflies found exclusively in OtiscoLake. These results may be evidence to suggest that OnondagaLake is limited by dispersal. The ability of more sensitive lentic mayfly species found regionally to colonize OnondagaLake in the future might be one good measure of success of the ongoing remediation effort for this lake.

Next, I compared various bioassessment metrics from substrates collected in OnondagaLake with OtiscoLake. I selected these candidate metrics with the help of preliminary data collected and analyzed from 13 lakes around NY State by the NYDEC SBU. We compared 11 metrics between OnondagaLake and OtiscoLake to determine which were able to distinguish between the lakes, and thus which were most effective in evaluating disturbed versus undisturbed lake conditions. It was determined that 3 of the 11 bioassessment metrics showed significant differences between the lakes most often. We also assessed these same 11 metrics between sites within OnondagaLake. This was important because only some sites within OnondagaLake are slated for future sediment remediation. We found that a different set of metrics were better at distinguishing between sites within the lake itself. This information has important implications that should be considered infuture monitoring protocols during and after the remediation ofOnondagaLake.

In closing, I would like to express my immense gratitude to the Edna Bailey Sussman Foundation for giving me this unique and rewarding opportunity. This internship provided me with thechance to work closely with the NYDEC and gain valuable insight and expertise from professionals currently working in the field of freshwater management. This research project is connected to a large-scale remediation project with high public exposure. The Edna Bailey Sussman Foundation will certainly be acknowledged in my thesis and all publications that result from this work.

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