Ms. S. (Sarian) Kosten: Aquatic ecosystems in hot water: Effects of climate on the functioning of shallow lakes

Global warming may have far reaching consequences for lakes. To investigate the potential climate effects we sampled 83 lakes in different climate regions in South America. The selected lakes were similar in size and depth while varying as much as possible in nutrient levels, such as phosphorus, within the different climate regions.

My research indicates that the negative effects of nutrient contamination are often stronger in a warm climate than in a cooler climate. In areas with few frost days shallow lakes may turn into a green algal soup without submerged vegetation at lower phosphorus levels than in areas with longer frost periods. This suggests that, if we want to conserve the submerged vegetation, phosphorus levels may have to be lowered in regions were climate change will decrease the number of frost days. Furthermore, my analyses point out that warmer lakes have a higher change to be dominated by cyanobacteria – a.k.a. blue-green algae – than colder lakes with the same level of nutrients. Finally my results suggest that cold lakes may start to emit more carbon dioxide when they warm up, which may further enhance climate change.