A Gulf Stream frontal eddy harbors a distinct microbiome compared to adjacent waters

Abstract

Marine microbiome community assembly and consequently biogeochemical cycling are shaped by past and current environments, as well as stochasticity, dispersal etc. To better understand the processes that structure marine microbial communities, we examine a cyclonic, Gulf Stream frontal eddy, whose microbiome potentially contains signatures of both the shelf community entrained during formation as well as current environmental conditions. In spite of the potential for eddy-driven upwelling to introduce nutrients and stimulate primary production, the eddy surface waters exhibit lower chlorophyll a along with a distinct and less even microbial community relative to the neighboring Gulf Stream waters. Although the eddy microbiome is distinct from the Gulf Stream's, especially in cyanobacteria (e.g. lower Trichodesmium and higher Prochlorococcus), it is most similar to the Gulf Stream, suggesting eddy microbiome assembly favors environmental filtering over historical contingencies. However, better delineation of the relative roles of ecological processes will likely require Lagrangian sampling throughout the photic zone to clarify the contribution of these mesoscale features to primary production and export as well as identifying the key processes driving microbiome assembly in the oceans.

The Impact of Gulf Stream Frontal Eddies on Ecology and Biogeochemistry near Cape Hatteras

“…A companion study (Gronniger et al 2023), focused on the eddy microbiome, was undertaken on the same flow-through surface samples and similarly reveals differences in microbial community composition between water masses. Although samples were categorized differently, Gronniger et al (2023) found that the eddy harbored higher abundance of Prochlorococcus and lower abundances of Synechococcus and Pelagibacteraceae . However, despite differences between the Gulf Stream and eddy microbiomes, including higher abundances of Prochlorococcus in the eddy and higher abundances of the nitrogen-fixer Trichodesmium in the Gulf Stream (see also Figure 6), the eddy is most similar to the Gulf Stream relative to the other water masses, suggesting that assembly of the eddy microbiome is primarily determined by environmental filtering in these warm, low nutrient waters.…”

“…A companion study (Gronniger et al, 2023), focused on the eddy microbiome, was undertaken on the same flow-through surface samples and similarly reveals differences in microbial community composition between water masses. This companion study found that the eddy harbored higher abundance of Prochlorococcus and lower abundances of Synechococcus and Pelagibacteraceae .…”

“…However, despite differences between the Gulf Stream and eddy microbiomes, including higher abundances of Prochlorococcus in the eddy and higher abundances of the nitrogen-fixer Trichodesmium in the Gulf Stream (see also Figure 6), the eddy is most similar to the Gulf Stream relative to the other water masses, suggesting that assembly of the eddy microbiome is primarily determined by environmental filtering in these warm, low nutrient waters. Gronniger et al (2023) clustered the microbiome data and compared this to the physical delineations which showed that the discrete physical classes used here do not fully reflect microbiome clusters, likely due to the intense submesoscale dynamics in this region.…”

“…A companion study was conducted which focused on the microbiome of the eddy and adjacent water masses (Gronniger et al, 2023). This companion work ran 16SrRNA gene sequencing on the same water samples as our flow cytometry and nutrient analysis and compares the genetic makeup of microbes across the physical structures we studied.…”

“…This companion work ran 16SrRNA gene sequencing on the same water samples as our flow cytometry and nutrient analysis and compares the genetic makeup of microbes across the physical structures we studied. The results of Gronniger et al (2023)’s work are summarized and included in the discussion of this study for context.…”