The intersection of climate change, watershed influence, and phytoplankton dynamics in Lake Superior

Abstract

Climate change is leading to ecological shifts in lakes including altered thermal regimes, nutrient cycles, and food web structure. I explore how climate change is impacting phytoplankton dynamics in Lake Superior. I show that there are clear seasonal patterns in the development and degradation of the deep chlorophyll layer (DCL) and that as water temperatures warm there is a restructuring of the DCL, with a smaller thickness and greater maximum concentration at warmer temperatures. My research also shows that biological loading from rivers to Lake Superior may be an important source of seed populations for cyanobacterial blooms, particularly those characterized by low water temperature and high conductivity. Finally, I present a life cycle model to predict cyanobacterial blooms that integrates monitoring data and cyanobacteria life cycle stages. The model highlights the importance of phosphorus loading in promoting blooms and shows that akinete production may result in a decrease in peak summer vegetative biomass. This work lays the critical groundwork for understanding the impact of climate change on phytoplankton dynamics and their ecological implications.