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Summary The extent to which differences in microbial community structure result in variations in organic matter (OM) degradation is not well understood. Here, we tested the hypothesis that distinct marine microbial communities from North Atlantic surface and bottom waters would exhibit varying compositional succession and functional shifts in response to the same pool of complex high molecular weight (HMW‐OM). We also hypothesized that microbial communities would produce a broader spectrum of enzymes upon exposure to HMW‐OM, indicating a greater potential to degrade these compounds than reflected by initial enzymatic activities. Our results show that community succession in amended mesocosms was congruent with cell growth, increased bacterial production and most notably, with substantial shifts in enzymatic activities. In all amended mesocosms, closely related taxa that were initially rare became dominant at time frames during which a broader spectrum of active enzymes were detected compared to initial timepoints, indicating a similar response among different communities. However, succession on the whole‐community level, and the rates, spectra and progression of enzymatic activities, reveal robust differences among distinct communities from discrete water masses. These results underscore the crucial role of rare bacterial taxa in ocean carbon cycling and the importance of bacterial community structure for HMW‐OM degradation.
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Bacterial biogeography of the Indian Ocean
Abstract Historically, our understanding of bacterial ecology in the Indian Ocean has been limited to regional studies that place emphasis on community structure and function within oxygen‐minimum zones. Thus, bacterial community dynamics across the wider Indian Ocean are largely undescribed. As part of Bio‐GO‐SHIP, we sequenced the 16S rRNA gene from 465 samples collected on sections I07N and I09N. We found that (1) there were 23 distinct bioregions within the Indian Ocean, (2) the southeastern gyre had the largest gradient in bacterial alpha‐diversity, (3) the Indian Ocean surface microbiome was primarily composed of a core set of taxa, and (4) bioregions were characterized by transitions in physical and geochemical conditions. Overall, we showed that bacterial community structure spatially delineated the surface Indian Ocean and that these microbially defined regions were reflective of subtle ocean physical and geochemical gradients. Therefore, incorporating metrics of in situ microbial communities into marine ecological regions traditionally defined by remote sensing will improve our ability to delineate warm, oligotrophic regions.
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- Award ID(s):
- 2023545
- PAR ID:
- 10477593
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 69
- Issue:
- 1
- ISSN:
- 0024-3590
- Format(s):
- Medium: X Size: p. 67-80
- Size(s):
- p. 67-80
- Sponsoring Org:
- National Science Foundation
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