A Salinity Threshold Separating Fungal Communities in the Baltic Sea

Area of Science:

• Aquatic Mycology
• Ecology
• Microbial Ecology

Background:

• Salinity is a key driver of microbial community structure.
• Aquatic fungal diversity in pelagic brackish ecosystems remains understudied.
• Brackish ecosystems, like estuaries, present unique environmental gradients.

Purpose of the Study:

• To investigate fungal community diversity and composition along a salinity gradient in the Baltic Sea.
• To identify critical salinity thresholds influencing fungal community structure.
• To compare fungal communities in freshwater- vs. marine-like conditions.

Main Methods:

• Exploration of fungal communities across a salinity decline from 34 to 3 PSU.
• Utilized 18S rRNA gene sequence analysis for community profiling.
• Analyzed three transects spanning approximately 2000 km in the Baltic Sea.

Main Results:

• Detected significant shifts in fungal community composition correlated with salinity.
• Identified a critical salinity threshold around 8 PSU.
• Below 8 PSU, communities were dominated by Chytridiomycota (freshwater-associated).
• Above 8 PSU, communities resembled marine types, with dominance by LKM11 group (Cryptomycota), Ascomycota, or Basidiomycota.

Conclusions:

• Salinity is a crucial environmental factor structuring pelagic fungal communities in brackish waters.
• Understanding salinity's role is vital for comprehending aquatic fungal diversity and ecological functions.
• The 8 PSU threshold indicates a significant transition point for fungal community composition.