The microbiome of the pelagic tunicate Dolioletta gegenbauri: A potential link between the grazing and microbial food web

Abstract

Bloom‐forming gelatinous zooplankton occur circumglobally and significantly influence the structure of pelagic marine food webs and biogeochemical cycling through interactions with microbial communities. During bloom conditions especially, gelatinous zooplankton are keystone taxa that help determine the fate of primary production, nutrient remineralization, and carbon export. Using the pelagic tunicate Dolioletta gegenbauri as a model system for gelatinous zooplankton, we carried out a laboratory‐based feeding experiment to investigate the potential ecosystem impacts of doliolid gut microbiomes and microbial communities associated with doliolid faecal pellets and the surrounding seawater. Metabarcoding targeting Bacteria and Archaea 16S rRNA genes/Archaea) and qPCR approaches were used to characterize microbiome assemblages. Comparison between sample types revealed distinct patterns in microbial diversity and biomass that were replicable across experiments. These observations support the hypothesis that through their presence and trophic activity, doliolids influence the structure of pelagic food webs and biogeochemical cycling in subtropical continental shelf systems where tunicate blooms are common. Bacteria associated with starved doliolids (representative of the resident gut microbiome) possessed distinct low‐biomass and low‐diversity microbial assemblages, suggesting that the doliolid microbiome is optimized to support a detrital trophic mode. Bacterial genera Pseudoalteromomas and Shimia were the most abundant potential core microbiome taxa, similar to patterns observed in other marine invertebrates. Exploratory bioinformatic analyses of predicted functional genes suggest that doliolids, via their interactions with bacterial communities, may affect important biogeochemical processes including nitrogen, sulphur, and organic matter cycling.

Insights into Ecological & Evolutionary Processes via community metabarcoding

“…The paper by Pereira et al. (2022) examined the microbiome of a marine tunicate and the potential role of the microbiomes in pelagic biogeochemical cycling and nutrient remineralisation. They showed that the trophic activity and faecal pellet processing of the tunicates may impact the structure of pelagic food webs and biogeochemical nitrogen, sulphur and carbon cycling.…”

Insights into Ecological & Evolutionary Processes via Community Metabarcoding

“…Using an elevational transect in the Swiss Alps they used transcriptome levels to show that metabolic activity of bacteria declined with increasing elevation, but activity of bacteriophages did not, highlighting a gap in our understanding of microbial predator-prey relationships and associated viral contributions to carbon, nitrogen and phosphorus cycling. The paper by Pereira et al (2022) examined the microbiome of a pelagic tunicate and the potential role of the microbiomes in pelagic biogeochemical cycling and nutrient remineralization. They showed that the trophic activity of the tunicates affects the structure of pelagic food webs and biogeochemical nitrogen, sulfur, and organic cycling.…”

Editorial 2024

“…Finally, our third Special Issue, Insights into Ecological & Evolutionary Processes via Community Metabarcoding includes ‘papers that highlight the power of high‐throughput sequencing (HTS) data to address classic questions in ecology and evolution, particularly focused on metabarcoding (amplicon) datasets in conjunction with complementary ‐omics data types and/or models/theory to infer overall ecosystem processes’ (Gillespie et al., 2023). The impressive collection of 44 manuscripts covers a wide range of topics: community assembly processes (Andujar et al., 2022; Arjona et al., 2022; Emerson et al., 2022; Govender et al., 2022; Guerrieri et al., 2022; Ip, Chang, Oh, et al., 2022; Kiemel et al., 2022; Li et al., 2022; Macheriotou et al., 2023; Menéndez‐Serra et al., 2023; Nappi et al., 2022; Noguerales et al., 2023; Overcast et al., 2023; Pino et al., 2023; Van der Loos et al., 2022; Wang et al., 2022), interaction networks (Ando et al., 2022; Bell et al., 2022; Dürrbaum et al., 2022; Encinas‐Viso et al., 2022; Ficetola & Taberlet, 2023; Graham et al., 2022; Ip, Chang, Tun, et al., 2022; Lowe et al., 2022; Lu et al., 2022; Lue et al., 2022; Pitteloud et al., 2022; Srivathsan et al., 2022; Tommasi et al., 2022), cross‐scale interactions and microbiomes (Brinker et al., 2022; Câmara dos Reis et al., 2022; Hu et al., 2022; Kivistik et al., 2022; Manthey et al., 2022; Merges et al., 2022; Michel et al., 2022; Molina et al., 2022; Navine et al., 2022; Pereira et al., 2022; Perez‐Lamarque & Morlon, 2022; Rolshausen et al., 2022), and invasive species/homogenization (Andrés et al., 2023; Graham et al., 2022; Hampel et al., 2022; Kennedy et al., 2022; Overcast et al., …”