Taxonomically and Functionally Distinct Ciliophora Assemblages Inhabiting Baltic Sea Ice

Area of Science:

• Microbial Ecology
• Marine Biology
• Protistology

Background:

• Ciliophora are vital unicellular eukaryotes in aquatic ecosystems.
• Sea ice provides a unique habitat with saline water pockets where Ciliophora can thrive.
• Understanding Ciliophora in sea ice is crucial for assessing polar marine ecosystem health.

Purpose of the Study:

• To identify and functionally assign Ciliophora 18S ribosomal RNA reads from winter sea ice and under-ice water.
• To compare the taxonomic and functional diversity of Ciliophora assemblages in sea ice versus water column habitats.
• To investigate the impact of changing climate on sea ice habitats and associated Ciliophora communities.

Main Methods:

• Phylogenetic placement of Ciliophora 18S ribosomal RNA reads.
• Functional assignment based on taxonomic information.
• Comparative analysis of Ciliophora assemblages in sea ice and water samples collected during winter.

Main Results:

• Sea ice Ciliophora assemblages exhibited lower taxonomic and functional richness compared to under-ice water.
• Ciliophora diversity remained stable seasonally, but assemblages shifted, with distinct planktonic dominance (Choreotrichida, Oligotrichida) in water.
• Sea ice harbored surface-oriented, omnivorous, bacterivorous, parasitic, and heterotrophic Ciliophora, differing from the mixotrophic-dominated water column.

Conclusions:

• Sea ice offers a distinct, albeit less diverse, habitat for Ciliophora compared to the water column.
• Assemblages in sea ice are adapted to specific niches, including surface-oriented and heterotrophic lifestyles.
• Diminishing sea ice extent due to climate change poses a significant threat to these unique marine microbial habitats.