Rising temperatures are leading to extended, late-summer weeks of water stratification in lakes, promoting oxygen deprivation in the water with negative consequences for fish and other species. A study of some lakes found the amount of low oxygen water is increasing by 0.9% to 1.7% per decade on average and the volume of lake water lacking oxygen increased by more than 50% from three decades ago. Reducing oxygen in the water might see a buildup of methane. Nutrients like phosphorus from agricultural fertilizer, released from unsettled lake sediment may enter the water column, increasing the likelihood of harmful algal. Projected warming rates mean even greater increases in the amount of oxygen-depleted water in the future is likely.
https://news.cornell.edu/stories/2022/12/warming-climate-prompts-harmful-oxygen-loss-lakes