Salp blooms increase carbon export 5-fold in the Southern Ocean

Décima, Moira; Stukel, Michael R.; Nodder, Scott D.; Gutiérrez‐Rodríguez, Andres; Selph, K. E.; Santos, Adriana Lopes dos; Safi, Karl; Kelly, Thomas B; Deans, Fenella; Morales, Sergio E.; Baltar, Federico; Latasa, Mikel; Gorbunov, Maxim Y.; Pinkerton, Matt

doi:10.1101/2022.02.07.479467

Cited by 3 publications

(1 citation statement)

References 60 publications

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“…Using mean values from Figure 6 , and NPP above, including all salp‐mediated export processes, increases the E z ratio to 18%, which is 1.5‐fold higher than the E z ratio calculated excluding salp‐mediated export of 12% (Table 1 ). Similarly, a recent study in the Southern Ocean found that the E z ratio of 5%–10% in waters without salps increased to 42%–46% in waters with salps, due to the export of salp fecal pellets (Décima et al., 2022 ).…”

Section: Discussionmentioning

confidence: 86%

The Outsized Role of Salps in Carbon Export in the Subarctic Northeast Pacific Ocean

Steinberg

Stamieszkin

Maas

et al. 2022

Global Biogeochemical Cycles

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Periodic blooms of salps (pelagic tunicates) can result in high export of organic matter, leading to an “outsized” role in the ocean's biological carbon pump (BCP). However, due to their episodic and patchy nature, salp blooms often go undetected and are rarely included in measurements or models of the BCP. We quantified salp‐mediated export processes in the northeast subarctic Pacific Ocean in summer of 2018 during a bloom of Salpa aspera. Salps migrated from 300 to 750 m during the day into the upper 100 m at night. Salp fecal pellet production comprised up to 82% of the particulate organic carbon (POC) produced as fecal pellets by the entire epipelagic zooplankton community. Rapid sinking velocities of salp pellets (400–1,200 m d−1) and low microbial respiration rates on pellets (<1% of pellet C respired day−1) led to high salp pellet POC export from the euphotic zone‐up to 48% of total sinking POC across the 100 m depth horizon. Salp active transport of carbon by diel vertical migration and carbon export from sinking salp carcasses was usually <10% of the total sinking POC flux. Salp‐mediated export markedly increased BCP efficiency, increasing by 1.5‐fold the proportion of net primary production exported as POC across the base of the euphotic zone and by 2.6‐fold the proportion of this POC flux persisting 100 m below the euphotic zone. Salps have unique and important effects on ocean biogeochemistry and, especially in low flux settings, can dramatically increase BCP efficiency and thus carbon sequestration.

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Section: Discussionmentioning

confidence: 86%

The Outsized Role of Salps in Carbon Export in the Subarctic Northeast Pacific Ocean

Steinberg

Stamieszkin

Maas

et al. 2022

Global Biogeochemical Cycles

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The microbiome of the pelagic tunicate Dolioletta gegenbauri: A potential link between the grazing and microbial food web

et al. 2022

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Bloom‐forming gelatinous zooplankton occur circumglobally and significantly influence the structure of pelagic marine food webs and biogeochemical cycling through interactions with microbial communities. During bloom conditions especially, gelatinous zooplankton are keystone taxa that help determine the fate of primary production, nutrient remineralization, and carbon export. Using the pelagic tunicate Dolioletta gegenbauri as a model system for gelatinous zooplankton, we carried out a laboratory‐based feeding experiment to investigate the potential ecosystem impacts of doliolid gut microbiomes and microbial communities associated with doliolid faecal pellets and the surrounding seawater. Metabarcoding targeting Bacteria and Archaea 16S rRNA genes/Archaea) and qPCR approaches were used to characterize microbiome assemblages. Comparison between sample types revealed distinct patterns in microbial diversity and biomass that were replicable across experiments. These observations support the hypothesis that through their presence and trophic activity, doliolids influence the structure of pelagic food webs and biogeochemical cycling in subtropical continental shelf systems where tunicate blooms are common. Bacteria associated with starved doliolids (representative of the resident gut microbiome) possessed distinct low‐biomass and low‐diversity microbial assemblages, suggesting that the doliolid microbiome is optimized to support a detrital trophic mode. Bacterial genera Pseudoalteromomas and Shimia were the most abundant potential core microbiome taxa, similar to patterns observed in other marine invertebrates. Exploratory bioinformatic analyses of predicted functional genes suggest that doliolids, via their interactions with bacterial communities, may affect important biogeochemical processes including nitrogen, sulphur, and organic matter cycling.

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Quantifying biological carbon pump pathways with a data-constrained mechanistic model ensemble approach

Stukel

Décima²,

Landry³

2022

Biogeosciences

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Abstract. The ability to constrain the mechanisms that transport organic carbon into the deep ocean is complicated by the multiple physical, chemical, and ecological processes that intersect to create, transform, and transport particles in the ocean. In this paper we develop and parameterize a data-assimilative model of the multiple pathways of the biological carbon pump (NEMUROBCP). The mechanistic model is designed to represent sinking particle flux, active transport by vertically migrating zooplankton, and passive transport by subduction and vertical mixing, while also explicitly representing multiple biological and chemical properties measured directly in the field (including nutrients, phytoplankton and zooplankton taxa, carbon dioxide and oxygen, nitrogen isotopes, and 234Thorium). Using 30 different data types (including standing stock and rate measurements related to nutrients, phytoplankton, zooplankton, and non-living organic matter) from Lagrangian experiments conducted on 11 cruises from four ocean regions, we conduct an objective statistical parameterization of the model and generate 1 million different potential parameter sets that are used for ensemble model simulations. The model simulates in situ parameters that were assimilated (net primary production and gravitational particle flux) and parameters that were withheld (234Thorium and nitrogen isotopes) with reasonable accuracy. Model results show that gravitational flux of sinking particles and vertical mixing of organic matter from the euphotic zone are more important biological pump pathways than active transport by vertically migrating zooplankton. However, these processes are regionally variable, with sinking particles most important in oligotrophic areas of the Gulf of Mexico and California Current, sinking particles and vertical mixing roughly equivalent in productive coastal upwelling regions and the subtropical front in the Southern Ocean, and active transport an important contributor in the eastern tropical Pacific. We further find that mortality at depth is an important component of active transport when mesozooplankton biomass is high, but it is negligible in regions with low mesozooplankton biomass. Our results also highlight the high degree of uncertainty, particularly amongst mesozooplankton functional groups, that is derived from uncertainty in model parameters. Indeed, variability in BCP pathways between simulations for a specific location using different parameter sets (all with approximately equal misfit relative to observations) is comparable to variability in BCP pathways between regions. We discuss the implications of these results for other data-assimilation approaches and for studies that rely on non-ensemble model outputs.

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Salp blooms increase carbon export 5-fold in the Southern Ocean

Cited by 3 publications

References 60 publications

The Outsized Role of Salps in Carbon Export in the Subarctic Northeast Pacific Ocean

The Outsized Role of Salps in Carbon Export in the Subarctic Northeast Pacific Ocean

The microbiome of the pelagic tunicate Dolioletta gegenbauri: A potential link between the grazing and microbial food web

Quantifying biological carbon pump pathways with a data-constrained mechanistic model ensemble approach

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