Ecological Risk Assessment


Lakewide Assessment of Lake Ontario Benthic Macroinvertebrate Communities

Overview and Objectives

This research will evaluate the composition and abundance of components of the benthic community of the western basin of Lake Ontario. These data are critical to understanding the mechanisms and permitting quantitative estimation of the benthic-pelagic flux of energy and nutrients of each basin. Special attention will be given to keystone invertebrate species (Dreissena spp., Diporeia spp.). The objective of this research is to provide a statistically valid and precise estimate of lakewide and habitat-specific benthic invertebrate abundance and biomass (defined by depth and substrate type) of the Lake Ontario in 2013. The trophic structure of Lake Ontario has seen dramatic changes over the past 20 years. Lake Ontario continues to be one of the most rapidly changing of the Great Lakes, reflecting the successes of remediation activities and the expression of both ongoing and novel stresses. The most significant events have related to amelioration of carbon and nutrient loadings to the lake. However, establishment of non-native exotic species, particularly dreissenid mussels, has resulted in substantial reallocation of biomass and redirection of energy flow. There is increasing evidence that energy flow patterns in Lake Ontario have changed to reflect increasing importance of benthic processes to overall trophic functioning. Phenomena typically associated with increasing eutrophication (rising spring total phosphorus concentrations, episodic blooms of blue-green algae, development of extensive filamentous algal mats at shorelines) are suspected to be either direct or indirect consequences of these altered trophic processes. The energy and nutrient pathways coupling the benthic and pelagic communities of Lake Ontario are only partially understood, and few quantitative data on benthic-pelagic coupling exist to validate or calibrate models or to quantify mechanisms and relationships. The decline of Diporeia clearly has the potential to reduce the carrying capacity of planktivorous fishes in the Great Lakes. Changes in invertebrate food resources might alter competitive interactions between planktivorous fishes, which may affect salmonid production, yellow perch recovery, lake whitefish recruitment and growth, and success of natural reproduction of lake trout. State and tribal fishery managers in the Great Lakes need to know the health of the forage base to make informed decisions on salmonid stocking and commercial fishing regulations and quotas.


Nalepa, T. F. and A.K. Elgin. 2016. Summary of a benthic macroinvertebrate survey in Lake Ontario in 2013. Project completion report submitted to NOAA. June, 2016, 14 pp. (Appendix 9)


Nalepa, T. F. 2015. Trends in benthic macroinvertebrates in Lake Ontario. Lake Ontario CSMI: Reporting and Planning Workshop. Burlington, ON, November, 2015.

Nalepa, T. F., A. K. Baldridge, P. Glyshaw*, L. Rudstram, and B. Weidel. 2016. Trends in the benthic macroinvertebrate community in Lake Ontario through 2013. 59th Annual Conference on Great Lakes Research, Guelph, ON, June, 2016.