Dataset Information

Ballasting by cryogenic gypsum enhances carbon export in a Phaeocystis under-ice bloom.

ABSTRACT: Mineral ballasting enhances carbon export from the surface to the deep ocean; however, little is known about the role of this process in the ice-covered Arctic Ocean. Here, we propose gypsum ballasting as a new mechanism that likely facilitated enhanced vertical carbon export from an under-ice phytoplankton bloom dominated by the haptophyte Phaeocystis. In the spring 2015 abundant gypsum crystals embedded in Phaeocystis aggregates were collected throughout the water column and on the sea floor at a depth below 2?km. Model predictions supported by isotopic signatures indicate that 2.7?g?m-2 gypsum crystals were formed in sea ice at temperatures below -6.5?°C and released into the water column during sea ice melting. Our finding indicates that sea ice derived (cryogenic) gypsum is stable enough to survive export to the deep ocean and serves as an effective ballast mineral. Our findings also suggest a potentially important and previously unknown role of Phaeocystis in deep carbon export due to cryogenic gypsum ballasting. The rapidly changing Arctic sea ice regime might favour this gypsum gravity chute with potential consequences for carbon export and food partitioning between pelagic and benthic ecosystems.

SUBMITTER: Wollenburg JE

PROVIDER: S-EPMC5956002 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Ballasting by cryogenic gypsum enhances carbon export in a Phaeocystis under-ice bloom.

Wollenburg J E JE Katlein C C Nehrke G G Nöthig E-M EM Matthiessen J J Wolf-Gladrow D A DA Nikolopoulos A A Gázquez-Sanchez F F Rossmann L L Assmy P P Babin M M Bruyant F F Beaulieu M M Dybwad C C Peeken I I

Scientific reports 20180516 1

Mineral ballasting enhances carbon export from the surface to the deep ocean; however, little is known about the role of this process in the ice-covered Arctic Ocean. Here, we propose gypsum ballasting as a new mechanism that likely facilitated enhanced vertical carbon export from an under-ice phytoplankton bloom dominated by the haptophyte Phaeocystis. In the spring 2015 abundant gypsum crystals embedded in Phaeocystis aggregates were collected throughout the water column and on the sea floor a ...[more]

PMID: 29769577

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Project description:Greater diversity of eukaryotic phytoplankton than expected has been revealed recently through molecular techniques, but little is known about their temporal dynamics or fate in the open ocean. Here, we examined size-fractionated eukaryotic phytoplankton communities from the surface to abyssopelagic zone (5,000 m) throughout the year, by tracking sequence variants of the 18S rRNA gene in the western subtropical North Pacific. The oceanographic conditions were divided into two periods, stratification and mixing, between which the surface phytoplankton community differed. During the mixing period, the abundance of large phytoplankton (?3 ?m) increased, with diatoms and putative Pseudoscourfieldia marina dominating this fraction. Picophytoplankton (<3 ?m) also increased during the mixing period and were dominated by Mamiellophyceae. Taxa belonging to prasinophytes (including Ps. marina and Mamiellophyceae) were observed in the epipelagic zone throughout the year, and thus likely seeded the seasonal bloom that occurred during the mixing period. In contrast, diatoms observed during the mixing period mostly represented taxa unique to that period, including coastal species. Numerical particle backtracking experiments indicated that water masses in the surface layer could be transported from coastal areas to the study site. Gene sequences of coastal diatoms were present in the abyssopelagic zone. Therefore, allochthonous species drove the seasonal bloom and could be transported to deep waters. In the abyssopelagic zone, the relative abundance of Ps. marina in deep waters was similar to or higher than that of diatoms during the mixing period. Among picophytoplankton, Mamiellophyceae made up a significant fraction in the abyssopelagic zone, suggesting that prasinophytes are also involved in carbon export. Our molecular survey showed that these previously overlooked phytoplankton species could contribute significantly to the seasonal bloom and biological pump in the subtropical open ocean.

Dataset Information

Ballasting by cryogenic gypsum enhances carbon export in a Phaeocystis under-ice bloom.

Publications

Ballasting by cryogenic gypsum enhances carbon export in a Phaeocystis under-ice bloom.

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