Diel study reveals increased nighttime bacterial activity and its connection to organic compounds in the ocean

The linkages between dissolved organic matter (DOM) dynamics and bacterial activity (BAct) are key to regulating carbon fluxes in marine food webs. While transcriptional activities have shown diel patterns, the connections between BAct and DOM on the diel timescale remain unclear. This study explored how bacterioplankton transform DOM over diel cycles in the euphotic and upper twilight zones (to 300 m) of the North Atlantic subtropical gyre. BAct peaked at night in the euphotic zone, following daytime maxima in chlorophyll fluorescence, suggesting a delayed bacterial response to photosynthetic activity. Our data show nighttime BAct exceeded daytime rates 34-47% under dark incubations. Total dissolved amino acids (TDAA) concentrations were lowest at night in the upper twilight waters, indicating nighttime DOM consumption by bacterioplankton. Additionally, we observed that diel vertical migrators could contribute to the oscillation of labile DOM, such as TDAA, although their irregularity requires more detailed studies. BAct shifted DOM composition from fresher to more degraded forms, likely driven by bacterioplankton lineages such as SAR11, Rhodospirillaceae, and SAR202. Our findings show that daytime photosynthesis drives DOM production, while enhanced nighttime heterotrophic BAct facilitates its consumption and transformation, highlighting notable fluctuations in microbial processes and carbon cycling on a diel scale.

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Publication Details

Journal
Communications Biology
Published
2025-11-26
DOI
https://doi.org/10.1038/s42003-025-09085-6
Primary Topic
Marine and coastal ecosystems
Type
article
Field-Weighted Citation Impact
0.00

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article

Diel study reveals increased nighttime bacterial activity and its connection to organic compounds in the ocean

Luis M. Bolaños, Fabian Wittmers, Stephen J. Giovannoni, Keri Opalk et al.
Communications Biology
Marine and coastal ecosystems
article

Diel study reveals increased nighttime bacterial activity and its connection to organic compounds in the ocean

Luis M. Bolaños, Fabian Wittmers, Stephen J. Giovannoni, Keri Opalk, Ruth Curry, Melissa C. Kido Soule, Elisa R. Halewood, Leocadio Blanco‐Bercial, Hannah Gossner, Rachel Parsons, Krista Longnecker, Kevin L. Vergin, Alexandra Z. Worden, Craig A. Carlson, Gretchen J. Swarr, Amy E. Maas, Elizabeth B. Kujawinski, Shuting Liu, Rod Johnson
article en

Abstract

The linkages between dissolved organic matter (DOM) dynamics and bacterial activity (BAct) are key to regulating carbon fluxes in marine food webs. While transcriptional activities have shown diel patterns, the connections between BAct and DOM on the diel timescale remain unclear. This study explored how bacterioplankton transform DOM over diel cycles in the euphotic and upper twilight zones (to 300 m) of the North Atlantic subtropical gyre. BAct peaked at night in the euphotic zone, following daytime maxima in chlorophyll fluorescence, suggesting a delayed bacterial response to photosynthetic activity. Our data show nighttime BAct exceeded daytime rates 34-47% under dark incubations. Total dissolved amino acids (TDAA) concentrations were lowest at night in the upper twilight waters, indicating nighttime DOM consumption by bacterioplankton. Additionally, we observed that diel vertical migrators could contribute to the oscillation of labile DOM, such as TDAA, although their irregularity requires more detailed studies. BAct shifted DOM composition from fresher to more degraded forms, likely driven by bacterioplankton lineages such as SAR11, Rhodospirillaceae, and SAR202. Our findings show that daytime photosynthesis drives DOM production, while enhanced nighttime heterotrophic BAct facilitates its consumption and transformation, highlighting notable fluctuations in microbial processes and carbon cycling on a diel scale.

Communications BiologyVol. 8(1)
Bermuda Institute of Ocean Sciences (BM), Oregon State University (US), Marine Biological Laboratory (US), University of California, Santa Barbara (US), University of Exeter (GB), Microbial ID (United States) (US), Kean University (US), Woods Hole Oceanographic Institution (US)
Oregon State University, University of California, Santa Barbara, Division of Ocean Sciences
Openalex Percentile: Top 64%
Marine and coastal ecosystems
DOIOpen Access PDFOpenAlex
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