Study of zooplankton communities in Area of Concern (Toronto Harbour).

During monthly surveys of Toronto Harbour in 2016, Fisheries and Oceans Canada (DFO) Food-webs and Ecosystem Research determined that the inner harbour was impaired for phytoplankton and zooplankton populations based on finding very few large zooplankton and high rates of bacterial growth. However, the source of this impairment could not be identified, and this sampling was within the main inner harbour only. From 2018-2022 DFO returned to include important fish habitat restoration locations within the Toronto Islands and in Tommy Thompson Park (embayments and habitat cells). We find high annual and seasonal variability in community composition, but consistently find that zooplankton in the surrounding embayment's, Toronto Islands, and the habitats within Tommy Thompson Park have higher densities and more seasonal variability compared to the inner harbour. Physical water characteristics in the inner harbor such as temperature, turbidity and nutrient do change seasonally compared to the surrounding habitats, yet low zooplankton counts of particular species groups still persists. We will summarize the report assessing plankton populations and discuss implications for fish populations. [ABSTRACT FROM AUTHOR]