Linkage between copepods and bacteria in the North Atlantic Ocean

Abstract

Copepods and bacteria are fundamental components of the pelagic food web and play a major role in biogeochemical cycles. Marine bacteria have a free-living or particleattached lifestyle, but as members of the microbial food web, the only biotic interaction of bacteria is commonly assumed to be with their predators (protists and/or viruses). However, a copepod's body is highly enriched in organic matter and harbors a large and complex bacterial community. The aim of this study was to compare the composition of the free-living bacterial community of the open Atlantic to that associated with copepods. We used 454 highthroughput sequencing of the 16S rRNA gene to decipher the bacterial community composition associated with this zooplankton group and the ambient water. Significant differences were found between the bacterial communities associated with the dominant copepod families (Calanoida: Centropagidae and Clausocalanidae; Cyclopoida: Corycaeidae, Oncaeidae, and Lubbockiidae) and the ambient water. Bacilli and Actinobacteria dominated the copepodassociated community and Alphaproteobacteria, Deltaproteobacteria, and Synechococcus dominated the free-living community. However, the presence of shared bacterial operational taxonomic units (OTUs) between these 2 distinct habitats suggests a dynamic exchange of bacteria between seawater and copepods. Taken together, our results support the hypothesis that the interior and exterior surfaces of copepods provide a specific niche with a strong selective pressure for bacteria. © Inter-Research 2014.