Unicellular Eukaryotic Community Response to Temperature and Salinity Variation in Mesocosm Experiments

Area of Science:

• Marine ecology
• Microbial ecology
• Climate change impacts

Background:

• Climate change significantly impacts marine biodiversity.
• Biodiversity shifts can alter community sensitivity to environmental changes.

Purpose of the Study:

• To investigate the combined effects of heat shock and salinity changes on marine plankton communities.
• To assess the impact on unicellular eukaryotic plankton in the Baltic and Mediterranean seas.

Main Methods:

• Mesocosm experiments simulating heat shock (+6°C) and salinity changes (-5 psu, +5 psu).
• Next Generation Sequencing to analyze Operational Taxonomic Unit (OTU) richness, taxonomic and functional composition, and rRNA:rDNA ratios.

Main Results:

• Heat shock reduced OTU richness by 21% (Baltic) and 14% (Mediterranean).
• Communities shifted towards smaller phytoplankton and heterotrophic OTUs post-heat shock.
• Salinity changes drastically altered community composition, with <18% shared OTUs across conditions.
• Heat shock influenced subsequent salinity sensitivity by removing sensitive or tolerant taxa.

Conclusions:

• Marine heat waves decrease plankton biodiversity and alter community structure.
• Salinity is a critical factor shaping plankton communities.
• Biodiversity loss from warming affects plankton's resilience to other environmental stressors like salinity shifts.