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Benthic Microalgae Respond More Strongly to Warming and Salinity Than Zooplankton
Leena Virta1,2, Jonna Engström-Öst1,3
1Tvärminne Zoological Station University of Helsinki Hanko Finland.
Ecology and Evolution
|June 8, 2026
Summary
Warming decreased diatom diversity but increased zooplankton diversity in the Baltic Sea. Salinity changes impacted diatoms more than zooplankton, challenging previous hypotheses about climate change effects on aquatic ecosystems.
Area of Science:
- Marine ecology
- Climate change research
- Aquatic ecosystem functioning
Background:
- High-latitude regions experience amplified warming.
- The impact of simultaneous stressors like warming and salinity changes on aquatic trophic levels remains unclear.
- Understanding these effects is crucial for predicting the future of marine ecosystems.
Purpose of the Study:
- To investigate the effects of increased temperature and decreased salinity on Baltic Sea benthic diatoms and zooplankton.
- To assess impacts on diversity, functional traits, and biomass.
- To test hypotheses regarding the differential vulnerability of lower (diatoms) and higher (zooplankton) trophic levels to climate change stressors.
Main Methods:
- An indoor mesocosm experiment was conducted using Baltic Sea organisms.
- Treatments included ambient vs. +5°C warming and five salinity levels (3-7 PSU).
- Measurements focused on species and trait diversity, and biomass of diatoms and zooplankton.
Main Results:
- Warming reduced benthic diatom species and trait diversity but increased zooplankton diversity.
- The interaction of warming and decreasing salinity significantly affected benthic diatoms.
- Salinity changes did not impact zooplankton, suggesting adaptation to local conditions.
Conclusions:
- Multiple stressors significantly impact aquatic communities, with complex effects on different trophic levels.
- Contrary to hypotheses, Baltic zooplankton showed resilience to warming and salinity changes, while diatoms were more sensitive to salinity thresholds.
- The findings highlight the need for nuanced predictions of climate change impacts on marine food webs.
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