Nearshore-Offshore Planktonic Food Web Dynamics in Lake Ontario

Session: 54. - Food Web Ecology and Dynamics of Lake Ontario: Nearshore ? Pelagic Linkages

Kelly Bowen, Fisheries and Oceans Canada, [email protected]
Robin Rozon, Fisheries & Oceans Canada, [email protected]
Warren Currie, Fisheries and Oceans Canada, [email protected]
Mark Fitzpatrick, Fisheries & Oceans Canada, [email protected]

Abstract

Phytoplankton and zooplankton communities in Lake Ontario have undergone substantial changes in the last two decades as a result of phosphorus control, changes in alewife populations and the spread of exotic species including quagga mussels and the predatory cladocerans Bythotrephes and Cercopagis. We look at spatial and temporal shifts in chlorophyll, zooplankton and rotifer species composition, biomass and production at several monitoring stations in the Canadian waters of Lake Ontario. We examine nearshore to offshore gradients using both traditional vertical net hauls and emerging technologies such as a towed sensor array including a laser optical plankton counter. These surveys have been carried out in the western basin off Hamilton, the Toronto Harbour area and in the Kingston Basin, and support our understanding of pelagic food web dynamics. Changes in zooplankton community structure, such as the shift to Daphnia galeata mendotae from D. retrocurva in 2016, can be related to changes in planktivorous fish densities and subsequent fluctuations in Bythotrephes populations. Ongoing monthly monitoring of the lower food web at a few index stations provides valuable temporal data to “fill in the gaps” between intensive CSMI monitoring years in Lake Ontario.

1. Keyword
zooplankton

2. Keyword
Bythotrephes cederstroemii

3. Keyword
biomonitoring