Zooplankton community dynamics in the Trent Seven Waterway along Lake Simcoe and Lake Couchiching

Abstract

The Trent Severn Waterway (TSW) is a 386km channel that connects Lake Ontario to Georgian Bay. There is a lack of information on the water quality in the nearshore region of the TSW specifically in regards to the planktonic communities. Zooplankton are key components of aquatic ecosystems since they graze on phytoplankton and are preyed upon by planktivorous fish. Therefore, changes to their community will have significant impacts to lower and upper trophic levels. The main objectives of this research are to (i) provide baseline data on zooplankton community dynamics in the nearshore region of the TSW; and (ii) determine if zooplankton can effectively be used as water quality indicators in this area. Plankton and limnologic data sampling occurred at eight nearshore sites in Lake Simcoe and Lake Couchiching along the TSW over ten months from 2015-2016. A deepwater transect in Lake Couchiching was sampled over three seasons at varying depths. Environmental variables were collected to indicate water quality and included temperature, dissolved oxygen, chlorophyll a, pH, conductivity, total suspended load and nutrients (nitrate and total phosphorous). This study demonstrated that nearshore regions of the TSW exhibit a range of environmental conditions, varying from mesotrophic (N = 25.12 μg/L, TP = 10.83 μg/L, CHL a = 1.58 mg/m3) to mesoeutrophic conditions (N = 78.92 μg/L, TP = 31.31 μg/L, CHL a = 13.29 mg/m3). Additionally, zooplankton community composition exhibited significant variation spatially and temporally and water quality reflected the degree of anthropogenic disturbance. The highly disturbed sites (TR, LC, MB, PO) experienced higher nutrient concentrations, conductivity, zooplankton biomass and density with lower dissolved oxygen concentrations characteristic of degraded water quality. Zooplankton density ranged from 1.11x107 – 1.43 x108/L among all sites. Biomass varied from 26.09 – 221.16 μg/L with richness varying from 6.2 – 9.4. Diversity did not differ substantially (1.23 – 1.69). RDA found some species level response to environmental variables although multiple regression explained more variance in the data. High abundance of Bosmina longirostris in highly disturbed sites indicates more eutrophic conditions which supports other research. Long term monitoring of zooplankton can provide baseline data that localized effects from specific anthropogenic stressors can be compared.