Fjords of the western and northern regions of Svalbard harbour distinct bacterioplankton community structures.

Abstract

Fjords are highly dynamic ecosystems that are known to be sentinels to climate change due to increased glaciomarine interactions. The convergence and mixing of warm Atlantic water (AtW) and cold Arctic water (ArW) is known to influence the hydrodynamics and ecology of the Arctic fjords. However, most past studies were limited to single-fjord ecosystems, determining the baseline knowledge of inter-fjord comparison on bacterioplankton diversity and distribution patterns. In the present study, we investigated the bacterial diversity and community composition across three Arctic fjords located in the western and northern regions of Svalbard. Our observations show that the bacterial community structure varied significantly among the fjords, while abundant Operational Taxonomic Units (OTUs) were widespread (n = 100) between all the samples and rare OTUs (n = 2221) mainly contributed to these differences. Phylogenetic classification revealed that Alpha (27.3-55%) and Gamma-proteobacteria (16-51.3%), followed by Bacteroidota (17-35.7%) were dominant in the St.Jonsfjorden and Magdalenefjorden, while Verrucomicrobiota (up to 84.19%) and Actinobacteriota (up to 76.5%) were predominant in the Raudfjorden. Temperature, dissolved inorganic phosphate (DIP) and depth were found to significantly influence the community composition of abundant bacterial groups, whereas the rare bacterial groups were affected by temperature, DIP, dissolved inorganic nitrate (DIN), ammonium and depth. A comparative meta-analysis along with Kongsfjorden and Krossfjorden also showed that each fjord had a significantly different bacterioplankton community structure.