Role of zooplankton in determining the efficiency of the biological carbon pump

Cavan, Emma L.; Henson, Stephanie A.; Belcher, Anna; Sanders, Richard J.

doi:10.5194/bg-2016-251

Cited by 23 publications

(37 citation statements)

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“…Pelagic crustaceans such as krill can have a prominent role in regulating the magnitude of carbon stored in the ocean via the biological pump ( Fig. 1) 7,25 . During photosynthesis, unicellular phytoplankton transform dissolved inorganic carbon (DIC or CO 2 ), a portion of which originates from the atmosphere, into organic carbon in their cells in the surface ocean 26 ( Fig.…”

Section: Krill and Biogeochemical Cyclesmentioning

confidence: 99%

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The importance of Antarctic krill in biogeochemical cycles

et al. 2019

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Antarctic krill (Euphausia superba) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguinsbut they have another important role. With their large size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean's largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval Antarctic krill. O cean biogeochemical cycles are paramount in regulating atmospheric carbon dioxide (CO 2) levels and in governing the nutrients available for phytoplankton growth 1. As phytoplankton are essential in most marine food webs, biogeochemistry is also important in fuelling fishery production 2. The role of phytoplankton in atmospheric CO 2 drawdown and fish production has been the central focus of many biogeochemical studies (e.g., refs. 3,4). However, despite evidence of their potential importance, higher organisms (metazoa) such as zooplankton (e.g., copepods and salps), nekton (e.g., adult krill and fish), seabirds and mammals 5-12 , have received less attention concerning their roles in the global biogeochemical cycles. One of the main mechanisms by which metazoa can influence biogeochemical cycles is through the biological pump 1 (Fig. 1). The biological pump describes a suite of biological processes that ultimately sequester atmospheric CO 2 into the deep ocean on long timescales. During photosynthesis in the surface, ocean phytoplankton produce organic matter and a fraction (< 40 %) sinks to deeper waters 13. It is estimated that 5-12 Gt C is exported from the global surface ocean annually 14 , with herbivorous metazoa contributing to the biological pump by releasing fast-sinking faecal pellets, respiring carbon at depth originally assimilated in the surface ocean and by excreting nutrients near the surface promoting further phytoplankton

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Section: Krill and Biogeochemical Cyclesmentioning

confidence: 99%

“…growth 7,8 . It is essential that the role of metazoa in biogeochemical cycles is recognised 15 to improve the mechanistic understanding of the present-day environment.…”

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The importance of Antarctic krill in biogeochemical cycles

et al. 2019

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“…The sinking of phytoplankton aggregates might result from nutrient limitation at the end of the phytoplankton bloom (Thornton, ). Given the higher sinking speed and the mechanical protection of the faecal pellets, they might be associated with a high transfer efficiency to the mesopelagic ocean (Cavan et al, ). However, because of the very different composition and sinking speed of these export vectors, the carbon export fluxes associated with the b bp and fluorescence spikes cannot be quantified here.…”

Section: Resultsmentioning

confidence: 99%

Plankton Assemblage Estimated with BGC‐Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export

et al. 2017

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The Southern Ocean (SO) hosts plankton communities that impact the biogeochemical cycles of the global ocean. However, weather conditions in the SO restrict mainly in situ observations of plankton communities to spring and summer, preventing the description of biological successions at an annual scale. Here, we use shipboard observations collected in the Indian sector of the SO to develop a multivariate relationship between physical and bio‐optical data, and, the composition and carbon content of the plankton community. Then we apply this multivariate relationship to five biogeochemical Argo (BGC‐Argo) floats deployed within the same bio‐geographical zone as the ship‐board observations to describe spatial and seasonal changes in plankton assemblage. The floats reveal a high contribution of bacteria below the mixed layer, an overall low abundance of picoplankton and a seasonal succession from nano‐ to microplankton during the spring bloom. Both naturally iron‐fertilized waters downstream of the Crozet and Kerguelen Plateaus show elevated phytoplankton biomass in spring and summer but they differ by a nano‐ or microplankton dominance at Crozet and Kerguelen, respectively. The estimated plankton group successions appear consistent with independent estimations of particle diameter based on the optical signals. Furthermore, the comparison of the plankton community composition in the surface layer with the presence of large mesopelagic particles diagnosed by spikes of optical signals provides insight into the nature and temporal changes of ecological vectors that drive particle export. This study emphasizes the power of BGC‐Argo floats for investigating important biogeochemical processes at high temporal and spatial resolution.

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“…While the observed seasonality in small‐particle transfer efficiency is likely driven in large part by changes in stratification, it may also reflect changes in particle consumption. For example, increased summertime zooplankton abundance and metabolism might reduce particle export through grazing activities (Cavan et al, ). Alternatively, the microbial community could display an increased abundance or increased remineralization rates due to increased temperatures observed in the upper mesopelagic in summer (Rivkin & Legendre, ).…”

Section: Discussionmentioning

confidence: 99%

High‐Frequency Variability of Small‐Particle Carbon Export Flux in the Northeast Atlantic

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Henson

Rumyantseva

et al. 2018

Global Biogeochemical Cycles

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The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air‐sea CO 2 balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed‐layer pump: a seasonal net detrainment of particulate organic carbon (POC)‐rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small‐particle POC concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small‐particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed‐layer variations, we find that the mixed‐layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC·m −2 ·year −1 to the mesopelagic zone, contributing between 5% and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high‐frequency observations of export variability over the course of a full year. Our results support the deployment of bio‐optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual.

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Role of zooplankton in determining the efficiency of the biological carbon pump

Cited by 23 publications

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The importance of Antarctic krill in biogeochemical cycles

The importance of Antarctic krill in biogeochemical cycles

Plankton Assemblage Estimated with BGC‐Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export

High‐Frequency Variability of Small‐Particle Carbon Export Flux in the Northeast Atlantic

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