The Influence of a Ubiquitous Filter Feeder on Coastal Microbial Communities

Abstract

Doliolids are a unique study system for investigating the intricate relationship between pelagic tunicates and the marine microbial community. This study identified the eukaryotic and prokaryotic microbial taxa in wild-caught doliolids in the Northern California Current system. Doliolids were collected during bloom events identified at three different shelf locations with variable upwelling intensity. This study found that doliolids host a microbiome unique from that of the seawater surrounding them and that feeding by doliolids includes a range of prokaryotic microbial functional groups. This is the first study to identify that doliolids are a source of mortality for pelagic archaea, and the most abundant cell in the ocean, SAR11. A subset of doliolids were found to feed preferentially on the picocyanobacterium Synechococcus compared to the other major phytoplankter in the system, diatoms. By quantitatively focusing on three numerically abundant and ecologically important microbes Synechococcus, diatoms, and SAR11, these results indicate that doliolids are retaining SAR11 and Synechococcus at a higher rate than they are found in the seawater. Given the ability of doliolids to clear large portions of seawater by filtration and their high abundance in this system, the results suggest that doliolids are an important player in shaping microbial community structure, primary production, and carbon fate in an ecologically and economically important fisheries system of the Northern California Current.