Faculty Opinions recommendation of Seasonal rhythms of net primary production and particulate organic carbon flux describe biological pump efficiency in the global ocean.

Abstract. Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr−1, representing between 3 % and 1∕3 of oceanic CO2 uptake. Up to 1∕2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

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Large deep-sea zooplankton biomass mirrors primary production in the global ocean

Nature Communications ◽

10.1038/s41467-020-19875-7 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

S. Hernández-León ◽

R. Koppelmann ◽

E. Fraile-Nuez ◽

A. Bode ◽

C. Mompeán ◽

...

Keyword(s):

Organic Carbon ◽

Primary Production ◽

Deep Sea ◽

Large Scale ◽

Net Primary Production ◽

Deep Ocean ◽

Zooplankton Biomass ◽

Global Ocean ◽

Global Coupling ◽

Do So

AbstractThe biological pump transports organic carbon produced by photosynthesis to the meso- and bathypelagic zones, the latter removing carbon from exchanging with the atmosphere over centennial time scales. Organisms living in both zones are supported by a passive flux of particles, and carbon transported to the deep-sea through vertical zooplankton migrations. Here we report globally-coherent positive relationships between zooplankton biomass in the epi-, meso-, and bathypelagic layers and average net primary production (NPP). We do so based on a global assessment of available deep-sea zooplankton biomass data and large-scale estimates of average NPP. The relationships obtained imply that increased NPP leads to enhanced transference of organic carbon to the deep ocean. Estimated remineralization from respiration rates by deep-sea zooplankton requires a minimum supply of 0.44 Pg C y−1 transported into the bathypelagic ocean, comparable to the passive carbon sequestration. We suggest that the global coupling between NPP and bathypelagic zooplankton biomass must be also supported by an active transport mechanism associated to vertical zooplankton migration.

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The ballast effect of lithogenic matter and its influences on the carbon fluxes in the Indian Ocean

Biogeosciences ◽

10.5194/bg-16-485-2019 ◽

2019 ◽

Vol 16 (2) ◽

pp. 485-503 ◽

Cited By ~ 10

Author(s):

Tim Rixen ◽

Birgit Gaye ◽

Kay-Christian Emeis ◽

Venkitasubramani Ramaswamy

Keyword(s):

Indian Ocean ◽

Organic Carbon ◽

Spatial Variability ◽

Primary Production ◽

Carbon Flux ◽

Carbon Fluxes ◽

Matter Content ◽

Organic Carbon Flux ◽

The Indian Ocean ◽

Organic Carbon Fluxes

Abstract. Data obtained from long-term sediment trap experiments in the Indian Ocean in conjunction with satellite observations illustrate the influence of primary production and the ballast effect on organic carbon flux into the deep sea. They suggest that primary production is the main control on the spatial variability of organic carbon fluxes at most of our study sites in the Indian Ocean, except at sites influenced by river discharges. At these sites the spatial variability of organic carbon flux is influenced by lithogenic matter content. To quantify the impact of lithogenic matter on the organic carbon flux, the densities of the main ballast minerals, their flux rates and seawater properties were used to calculate sinking speeds of material intercepted by sediment traps. Sinking speeds in combination with satellite-derived export production rates allowed us to compute organic carbon fluxes. Flux calculations imply that lithogenic matter ballast increases organic carbon fluxes at all sampling sites in the Indian Ocean by enhancing sinking speeds and reducing the time of organic matter respiration in the water column. We calculated that lithogenic matter content in aggregates and pellets enhances organic carbon flux rates on average by 45 % and by up to 62 % at trap locations in the river-influenced regions of the Indian Ocean. Such a strong lithogenic matter ballast effect explains the fact that organic carbon fluxes are higher in the low-productive southern Java Sea compared to the high-productive western Arabian Sea. It also implies that land use changes and the associated enhanced transport of lithogenic matter from land into the ocean may significantly affect the CO2 uptake of the organic carbon pump in the receiving ocean areas.

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