Heatwave-Induced Thermal Stratification Shaping Microbial-Algal Communities Under Different Climate Scenarios as Revealed by Long-Read Sequencing and Imaging Flow Cytometry
Meirkhanova A. Zhumakhanova A. Len P. Schoenbach C. Levi E.E. Jeppesen E. Davidson T.A. Barteneva N.S.
August 2025Multidisciplinary Digital Publishing Institute (MDPI)
Toxins
2025#17Issue 8
The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were based on IPCC climate warming scenarios, enabling simulation of future warming conditions. Surface oxygen levels reached 19.37 mg/L, while bottom layers dropped to 0.07 mg/L during stratification. Analysis by FlowCAM revealed dominance of Cyanobacteria under ambient conditions (up to 99.2%), while Cryptophyta (up to 98.9%) and Chlorophyta (up to 99.9%) were predominant in the A2 and A2+50% climate scenarios, respectively. We identified temperature changes and shifts in nutrient concentrations, particularly phosphate, as critical factors in microbial community composition. Furthermore, five distinct Microcystis morphospecies identified by FlowCAM-based analysis were associated with different microbial clusters. The combined use of imaging flow cytometry, which differentiates phytoplankton based on morphological parameters, and nanopore long-read sequencing analysis has shed light into the dynamics of microbial communities associated with different Microcystis morphospecies. In our observations, a peak of algicidal bacteria abundance often coincides with or is followed by a decline in the Cyanobacteria. These findings highlight the importance of species-level classification in the analysis of complex ecosystem interactions and the dynamics of algal blooms in freshwater bodies in response to anthropogenic effects and climate change.
algicidal bacteria , FlowCam , imaging flow cytometry , long-read sequencing , microbial communities , Microcystis , thermal stratification
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Department of Biology, School of Sciences and Humanities, Nazarbayev University, Astana, 010000, Kazakhstan
WATEC, 8000, Denmark
Sino-Danish Centre for Education and Research, Beijing, 100049, China
Department of Biological Sciences and Centre for Ecosystem Research and Implementation, Middle East Technical University, Erdemli-Mersin, 33731, Turkey
Institute of Marine Sciences, Middle East Technical University, Mersin, Erdemli, 33731, Turkey
Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, 650500, China
The Environmental Research and Efficiency Cluster, Nazarbayev University, Astana, 010000, Kazakhstan
Department of Biology
WATEC
Sino-Danish Centre for Education and Research
Department of Biological Sciences and Centre for Ecosystem Research and Implementation
Institute of Marine Sciences
Institute for Ecological Research and Pollution Control of Plateau Lakes
The Environmental Research and Efficiency Cluster
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