Assessing nearshore water quality and biological condition in the Kawartha Lakes using a community science approach

Abstract

The Kawartha Lakes, located in south-central Ontario, are a popular tourist destination, with a growing permanent resident population. Consequently, land development in its watersheds continues, and the specific land-use – water quality relationships in this region are unknown. The nearshore zone is where land use has its first impacts on the lake, and provides vital habitat for most lake inhabitants at some point in their life cycle. Despite its importance, the nearshore zone is rarely monitored and further investigation is required to understand human impacts on the nearshore zone. My thesis aimed to elucidate the relationships between land use and the abiotic and biotic condition of the nearshore zone in the Kawartha Lakes. To examine Lake Scugog’s nearshore water quality patterns and relationship with land use, 12 volunteers collected water samples from spring to fall for three years. Land use had significant impacts on chloride at buffer scales and phosphorus at the sub-watershed scale. I also monitored the nearshore biotic community (phytoplankton, zooplankton, and macroinvertebrates) at eight sites in Lake Scugog. Two years of sampling found that macrophyte abundance significantly influenced the phytoplankton, zooplankton, and macroinvertebrate communities. During the pandemic restrictions in 2020, community scientists on 16 lakes collected monthly water samples from June-September. A subset of four lakes had nutrient data across 3-years (2019 - 2021), which allowed comparison of nutrient conditions before and during the pandemic. There were significant differences in water quality between watersheds and a notable impact of Lake Scugog on downstream lakes. There was not a significant impact of pandemic restrictions on nearshore water quality in these lakes. A focal study on Balsam, Cameron, Sturgeon, and Pigeon lakes involved nearshore water quality monitoring (2019 and 2021) and biological sample collection (2021). There was a separation of distinct water quality profiles that grouped Balsam and Cameron, and Sturgeon and Pigeon. Exploring relationships between land use, water quality, and the biotic communities I found that phosphorus was important for driving phytoplankton, zooplankton, and macroinvertebrate community abundance. Overall, these findings provide important information for lake managers in understanding the role of land-use and nearshore ecological condition in lake health.