Production and diversity of microorganisms associated with sinking particles in the subtropical North Pacific Ocean

Matthew J. Church, Eint Kyi, Robert O. Hall, David M. Karl, Markus Lindh, Alexa Nelson, Emma K. Wear

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Sinking particulate organic matter controls the flux of carbon (C) from the surface ocean to the deep sea. Microorganisms actively colonize particles, but the extent to which microbial metabolism influences particle export remains uncertain. We conducted experiments to quantify rates of bacterial production (derived based on 3H-leucine incorporation) and dark C-fixation (based on 14C-bicarbonate assimilation) associated with sinking particles collected from the base of the euphotic zone (175 m) in the subtropical North Pacific Ocean. Seawater was amended with sinking particles and rates of filter size-fractionated (0.2, 2, and 20 μm) bacterial production and dark C-fixation were measured. Sequencing of 16S ribosomal RNA (rRNA) gene amplicons revealed that microorganisms in the particle-amended treatments differed from those in the unamended seawater controls, with the particle treatments enriched in putative copiotrophic bacteria. The addition of sinking particles increased rates of bacterial production (by 6- to 9-fold), and to a lesser extent dark C-fixation (by 1.7- to 4.6-fold), relative to unamended controls, with most of the production associated with filter pore sizes < 20 μm. Normalizing production to concentrations of particulate C yielded rates that were statistically indistinguishable between particle-amended treatments and unamended controls. We then examined possible relationships between sinking particulate C flux attenuation and its supply to the mesopelagic waters, revealing that flux attenuation was positively related to increases in particulate C supply. Together with results from our experiments, we suggest processes that contribute to sinking particle disaggregation both increase flux attenuation and favor microbial mineralization of particle-derived organic matter.

Original languageEnglish
Pages (from-to)3255-3270
Number of pages16
JournalLimnology and Oceanography
Volume66
Issue number9
DOIs
StatePublished - Sep 2021

Funding

We thank Eric Grabowski, Blake Watkins, Karin Björkman, and Tara Clemente for their respective contributions to field and laboratory work associated with this study. We also appreciate the help of Benedetto Barone and Susan Curless for their leadership of the research cruises when this work was conducted. Total organic carbon analyses were conducted by the Carlson Microbial Oceanography Laboratory at the University of California Santa Barbara. Amplicon sequencing was conducted at the Hawai'i Institute for Marine Biology (HIMB) genetics core facility. We thank the captains and crew of the R/V  (KOK) for facilitating this work. This work was supported by a grant from the Simons Foundation (awards 329108 and 721252 to DMK, and 721221 to MJC). Ka'imikai‐O‐Kanaloa We thank Eric Grabowski, Blake Watkins, Karin Björkman, and Tara Clemente for their respective contributions to field and laboratory work associated with this study. We also appreciate the help of Benedetto Barone and Susan Curless for their leadership of the research cruises when this work was conducted. Total organic carbon analyses were conducted by the Carlson Microbial Oceanography Laboratory at the University of California Santa Barbara. Amplicon sequencing was conducted at the Hawai'i Institute for Marine Biology (HIMB) genetics core facility. We thank the captains and crew of the R/V Ka'imikai-O-Kanaloa (KOK) for facilitating this work. This work was supported by a grant from the Simons Foundation (awards 329108 and 721252 to DMK, and 721221 to MJC).

FundersFunder number
Simons Foundation721221, 721252, 329108
University of California at Santa Barbara

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