Salinity as a Determinant Structuring Microbial Communities in Coastal Lakes

Area of Science:

• Environmental microbiology
• Aquatic ecology
• Bacteriology

Background:

• Coastal lakes exhibit a range of salinity levels, influencing their ecological characteristics.
• Bacterioplankton communities are sensitive to environmental gradients, including salinity.
• Understanding microbial responses to salinity is crucial for assessing coastal ecosystem health.

Purpose of the Study:

• To investigate the response of bacterioplankton structure to varying salinity levels in southern Baltic Sea coastal lakes.
• To identify bacterial bioindicators for different salinity conditions (freshwater, transitional, brackish).
• To explore correlations between bacterioplankton composition and key physicochemical parameters.

Main Methods:

• Sampling of nine coastal lakes with salinity ranging from 0.2 to 5.2 PSU.
• Analysis of bacterioplankton structure and abundance.
• Statistical analysis to determine relationships between microbial communities, salinity, and environmental factors.

Main Results:

• Salinity was a key factor determining bacterioplankton spatial and seasonal distribution.
• Total bacterial numbers (TBN) decreased significantly with increasing salinity.
• Specific bacterial groups, including Proteobacteria (Alpha-, Gamma-, Beta-subclasses) and Actinobacteria, were identified as indicators for different salinity habitats.
• Actinobacteria and Deltaproteobacteria were characteristic of transitional lakes.

Conclusions:

• Bacterioplankton community structure is strongly influenced by salinity in coastal lake ecosystems.
• Proteobacteria and Actinobacteria can serve as effective bioindicators for salinity stress in low-salinity environments.
• Hydrological connectivity and saltwater intrusion are important considerations for the ecological assessment of coastal waters.