Justyna Wolinska at one of the artificially heated study lakes.| Photo: Slawek Cerbin
The IGB research team, led by Prof. Justyna Wolinska studied seasonal plankton communities in five artificially heated lakes in Poland, warmed by power plant discharge for six decades. These lakes are around two degrees Celsius warmer (annual mean) than surrounding lakes and thus serve as natural laboratories for simulating global warming. Using environmental DNA analyses, the researchers determined the composition of the phyto- and zooplankton in the five heated and five control lakes.
“The observed approximately 2.0°C temperature increase reflects climate change projections, and elevated phosphorus levels in heated lakes allowed us to assess interactions between warming and nutrients. Both factors, alone and in combination, drove pronounced and seasonally variable shifts in plankton diversity and community composition”, Justyna Wolinska summarised the results.
There were smaller seasonal differences in plankton in warmed lakes
Heated lakes were primarily characterized by green algae (30%), followed by chytrids (15%), and diatoms (11%). In contrast, control lake indicators were dominated by diatoms (17%), green algae (16%), golden algae (8%), and chytrids (6%). The seasonal changes in plankton communities were less pronounced in the warmed lakes.
Warming, particularly in combination with nitrogen and phosphorus enrichment, reduced plankton diversity in several groups, underscoring the ecological risks posed by warming–eutrophication interactions. Previous studies have shown that warming can exacerbate eutrophication by accelerating nutrient cycling, depleting oxygen levels, and enhancing primary production. These processes may trigger biodiversity loss, alter trophic interactions, and increase the frequency of harmful algal blooms. “Our findings emphasize the need to consider multiple, interacting stressors when predicting freshwater ecosystem responses to climate change”, said Justyna Wolinska.
