Abstract
Mesoscale eddies, prominent physical processes in the stratified ocean gyres, affect community composition and metabolic rates of both phytoplankton and heterotrophic bacterioplankton (free-living bacterial and archaeal) communities. We hypothesized that in situ differences in organic matter production would predispose bacterioplankton communities from cyclonic vs. anticyclonic eddies toward metabolic capabilities better suited to utilizing dissolved organic matter (DOM) from the phytoplankton groups commonly associated with each eddy polarity. To test this, we established dilution batch-culture bioassay incubations along a cyclone to anticyclone spatial transect in the North Pacific Subtropical Gyre. Unamended incubations, to assess spatial variability in ambient DOM bioavailability, and incubations amended with lysates of phytoplankton cultures were established and community growth and metabolic responses were assessed. Over timescales of days, lysate type was more influential than incubation origin: Prochlorococcus lysate was rapidly remineralized, while Emiliania huxleyi lysate was efficiently incorporated into biomass and developed a unique community of copiotrophic bacteria. Over timescales of 1 week to 1 month, eddy effects were indirectly apparent in their potential to promote metabolic processes related to DOM production and consumption. Surface lysate incubations showed priming of ambient DOM, that is, the remineralization of DOM, which was otherwise not bioavailable, in the presence of labile substrates. Some incubations originating from the deep chlorophyll maximum demonstrated signatures of chemoautotrophy fueled by nitrification, coincident with eddy-driven isopycnal uplift. We conclude that eddy polarity itself does not determine community-level bacterioplankton metabolic capabilities; however, mesoscale processes may indirectly affect slower, semi-labile organic matter processing in the oligotrophic ocean.
| Original language | English |
|---|---|
| Pages (from-to) | 1608-1622 |
| Number of pages | 15 |
| Journal | Limnology and Oceanography |
| Volume | 65 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 1 2020 |
Funding
This work was funded by the Simons Foundation through the Simons Collaboration on Ocean Processes and Ecology (SCOPE award #329108 to MJC), with additional support from Simons Foundation International's BIOS‐SCOPE program to CAC. Ship time was funded by the Schmidt Ocean Institute. We thank Trista Vick‐Majors, the SCOPE staff, Craig Nelson, and Wesley Sparagon for logistical and sampling assistance. cells were provided by Allison Coe and Penny Chisholm; lysate was provided by Nicholas Baetge and Kara Newman. Shuting Liu generously quantified amino acids. Brandon Stephens provided advice on biovolume measurements. We thank Sam Wilson and the officers and crew of the R/V for assistance at sea. John Ranieri conducted ddPCR and Keri Opalk measured TOC and TN. Two anonymous reviewers and members of the SCOPE and BIOS‐SCOPE projects provided valuable feedback on this work. Prochlorococcus E. huxleyi Falkor This work was funded by the Simons Foundation through the Simons Collaboration on Ocean Processes and Ecology (SCOPE award #329108 to MJC), with additional support from Simons Foundation International's BIOS-SCOPE program to CAC. Ship time was funded by the Schmidt Ocean Institute. We thank Trista Vick-Majors, the SCOPE staff, Craig Nelson, and Wesley Sparagon for logistical and sampling assistance. Prochlorococcus cells were provided by Allison Coe and Penny Chisholm; E. huxleyi lysate was provided by Nicholas Baetge and Kara Newman. Shuting Liu generously quantified amino acids. Brandon Stephens provided advice on biovolume measurements. We thank Sam Wilson and the officers and crew of the R/V Falkor for assistance at sea. John Ranieri conducted ddPCR and Keri Opalk measured TOC and TN. Two anonymous reviewers and members of the SCOPE and BIOS-SCOPE projects provided valuable feedback on this work.
| Funders | Funder number |
|---|---|
| 1756517 | |
| Simons Foundation | 329108 |
| Schmidt Ocean Institute |