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The microbiome of the pelagic tunicate Dolioletta gegenbauri: a potential link between the grazing and microbial food web
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  • Tiago Pereira,
  • Tina Walters,
  • Hisham El-Shaffey,
  • Holly Bik,
  • Marc Frischer
Tiago Pereira
University of Georgia
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Tina Walters
Skidaway Institute of Oceanography
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Hisham El-Shaffey
North Carolina State University at Raleigh
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Holly Bik
University of Georgia
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Marc Frischer
Skidaway Institute of Oceanography
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Abstract

Doliolids often form massive blooms during upwelling conditions in sub-tropical shelves. However, their trophic role, including their nutritious fecal pellets, in pelagic marine food webs remains poorly investigated. In this study, we performed three independent feeding experiments of cultured Dolioletta gegenbauri and used qPCR analysis and 16S rRNA metabarcoding to characterize the microbial community associated with full gut (FG) and empty (EG) doliolids, fresh (FP2Hrs) and senescing (FP24Hrs) fecal pellets, and the surrounding natural seawater (SW). Bacterial abundance (i.e., 16S rRNA gene copies) in EG samples was an order of magnitude lower than in SW and three orders lower than in FP24Hrs. Diversity analyses, based on the 16S rRNA metabarcoding data, supported a richer microbial community in SW, FP2Hrs, FP24Hrs, and FG samples. Furthermore, microbial community structure was determined by sample type, with FG samples appearing more similar to either FP2Hrs or FP24Hrs. These patterns resulted from the higher number of shared ASVs and consequently the contribution of similar major bacterial taxa (e.g., Rhodobacteraceae, Pirellulaceae). These observations support the hypothesis that there are significant ecological and trophic interactions between D. gegenbauri and the ocean microbiome. Predicted gene function recovered many genes related to key processes in the marine environment and supported greater similarity between FP2Hrs, FP24Hrs, and FG samples. These observations suggest that pelagic marine bacteria are utilized by D. gegenbauri to digest captured prey particles, and the subsequent release of fecal pellets supports the rapid proliferation of distinct microbial communities which likely influence key biogeochemical processes in the ocean.

Peer review status:UNDER REVIEW

01 Jan 2022Submitted to Molecular Ecology
03 Jan 2022Assigned to Editor
03 Jan 2022Submission Checks Completed
14 Jan 2022Reviewer(s) Assigned