Lake Erie's zooplankton community composition and relative abundance in the western basin (2010-17)

Session: Great Lakes Lower Trophic Level Community Dynamics (2)

Brenten Vercruysse, University of Windsor, [email protected]
Yingming Zhao, Ontario Ministry of Natural Resources, [email protected]
Gordon Douglas Haffner, Great Lakes Institute for Environmental Research, Univ. of Windsor, [email protected]

Abstract

The composition and relative abundance of Lake Erie’s western basin zooplankton community was studied between 2010 and 2017, with the aim to determine seasonal and annual changes in community assemblage. Samples were collected and preserved by the Ontario Ministry of Natural Resources and Forestry (Wheatley Ontario). Preliminary results (2010, 2012, 2014, 2016) reveal a consistent spring peak occurring in May to early June with the four most abundant groups of zooplankton being calanoid copepods, cyclopoid copepods, Bosmina and Daphnia; however, their relative abundances differ each year. We also observed a fairly consistent spring clearing event, when community densities decreased an average of 4400 organisms/m³ during June or early July. This average annual decline is skewed by a large 2016 spring mass, with community density decreasing 10 000 organisms/m³ in June of 2016. In results from the 2010-16 period there appears to be a depression in summer and early autumn Bosmina and Daphnia populations. Overall, these populations in late September have decreased from an average 513 organisms/m³ in 2012 to 149 organisms/m³ in 2016. Although Microcystis-containing harmful algal blooms generally occur during late summer months, it is unknown if these depressions are a result of the recent re-eutrophication of Lake Erie.