Emergence of Algal Blooms in a Large Macrophyte-Dominated Lake

Session: 41a. - Great Lakes Harmful Algal Blooms Research from Watershed Influence to Ecosystem Effects

Tyler Harrow-Lyle, University of Ontario Institute of Technology, [email protected]
Andrea Kirkwood, University of Ontario Institute of Technology, [email protected]

Abstract

Lake Scugog is a large, shallow lake in southern Ontario that supports productive macrophyte and fish communities. In recent years, Lake Scugog has been experiencing changes in the macrophyte community, including periodic population collapses of the non-native plant Myriophyllum spicatum, and the recent invasion of the non-native charophyte Nitellopsis obtusa. During initial baseline studies in 2016 of the macrophyte, phytoplankton, and invertebrate communities, several algal blooms (dominated by Microcystis sp.) occurred in Lake Scugog. This was unusual because there had been no previous reports of algal blooms in the lake. Subsequent field studies in 2017 documented several algal bloom events again, which were orders of magnitude higher in Microcystis cell density compared to 2016. As a first step in understanding the causes of algal blooms in Lake Scugog, we detected positive correlations between Microcystis and total nitrogen, N. obtusa, and Dreissena polymorpha. Structural equation modeling revealed a significant positive interaction between N. obtusa and D. polymorpha that explained a high degree of the variation in Microcystis biomass (r=0.90). Considering that algal blooms occurred during a drought year (2016) and a wet year (2017), our preliminary findings suggest that Lake Scugog may be at risk of undergoing a regime shift.

1. Keyword
algae

2. Keyword
Dreissena

3. Keyword
invasive species

4. Additional Keyword
Nitellopsis obtusa

5. Additional Keyword
Microcystis