Prokaryotic communities associated with the Arctic bryozoan Tricellaria ternata (Ellis & Solander, 1786) from Isfjorden, Svalbard: baseline characterization for future ecological assessments

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Microbiological data on the Arctic bryozoan Tricellaria ternata (Ellis and Solander, 1786) are reported for the first time. Bryozoan colony fragments, seawater, and sediment were collected from Isfjorden (western coast of Spitsbergen Island, Svalbard Archipelago), and prokaryotic communities were characterized through high-throughput 16S rRNA gene sequencing. Bryozoan-associated communities were dominated by Proteobacteria, Bacteroidota, Verrucomicrobiota, and Actinobacteriota, while seawater and sediment communities also included Firmicutes and Desulfobacterota. Although seawater shared some broad taxonomic groups with T. ternata -associated microbiomes, it showed distinct community composition at family and genus levels. Several bacterial taxa, including Leucothrix , Methylotenera , Pseudovibrio , and Pibocella , were enriched in bryozoan samples and not detected in the analyzed environmental samples; however, these patterns should be interpreted as preferential association or enrichment rather than evidence of strict host specificity, given the limited spatial and temporal sampling. Several detected taxa have previously been associated with microorganisms potentially involved in methane, sulfur, and nitrogen cycling, although these ecological functions represent inferred potential roles rather than directly demonstrated activities. This study provides a baseline for future investigations of host-associated microbial communities and their variability in Arctic ecosystems.