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  1. Article ; Online: Model estimates of metazoans' contributions to the biological carbon pump

    J. Pinti / T. DeVries / T. Norin / C. Serra-Pompei / R. Proud / D. A. Siegel / T. Kiørboe / C. M. Petrik / K. H. Andersen / A. S. Brierley / A. W. Visser

    Biogeosciences, Vol 20, Pp 997-

    2023  Volume 1009

    Abstract: The daily vertical migrations of fish and other metazoans actively transport organic carbon from the ocean surface to depth, contributing to the biological carbon pump. We use an oxygen-constrained, game-theoretic food-web model to simulate diel vertical ...

    Abstract The daily vertical migrations of fish and other metazoans actively transport organic carbon from the ocean surface to depth, contributing to the biological carbon pump. We use an oxygen-constrained, game-theoretic food-web model to simulate diel vertical migrations and estimate near-global (global ocean minus coastal areas and high latitudes) carbon fluxes and sequestration by fish and zooplankton due to respiration, fecal pellets, and deadfalls. Our model provides estimates of the carbon export and sequestration potential for a range of pelagic functional groups, despite uncertain biomass estimates of some functional groups. While the export production of metazoans and fish is modest ( ∼20 % of global total), we estimate that their contribution to carbon sequestered by the biological pump ( ∼800 PgC) is conservatively more than 50 % of the estimated global total ( ∼1300 PgC) and that they have a significantly longer sequestration timescale ( ∼250 years) than previously reported for other components of the biological pump. Fish and multicellular zooplankton contribute about equally to this sequestered carbon pool. This essential ecosystem service could be at risk from both unregulated fishing on the high seas and ocean deoxygenation due to climate change.
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Subject code 333 ; 551
    Language English
    Publishing date 2023-03-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article: Internal lee waves and baroclinic bores over a tropical seamount shark ‘hot-spot’

    Hosegood, P.J / A.S. Brierley / K. Adams / R. Proud / W.A.M. Nimmo-Smith

    Progress in oceanography. 2019 Jan. 22,

    2019  

    Abstract: Oceanographic observations were made with a subsurface oceanographic mooring over the summit and flanks of two neighbouring seamounts in the tropical Indian Ocean to identify processes that may be responsible for the aggregation of silvertip sharks ( ... ...

    Abstract Oceanographic observations were made with a subsurface oceanographic mooring over the summit and flanks of two neighbouring seamounts in the tropical Indian Ocean to identify processes that may be responsible for the aggregation of silvertip sharks (Carcharhinus albimarginatus) in the deep water drop-off surrounding the summits. The seamounts, which are in the Chagos Archipelago in the British Indian Ocean Territories, are narrow in horizontal extent (<10 km), have steeply sloping (>15°) sides that rise from depths of >600 m, and flat summits at a depth of 70 m. They are subjected to forcing at subinertial, basin-scales and local scales that include a mixed tidal regime and storm-generated near inertial waves. At the drop-off, at a depth of between 70 – 100 m, isotherms oscillate at both diurnal and semidiurnal frequencies with amplitudes of ∼20-30 m. The waves of tidal origin are accompanied by short period (∼5 minutes) internal waves with amplitudes O(10 m) and frequencies close to the local buoyancy frequency, N, within the thermocline which is the maximum frequency possible for freely propagating internal waves. The tidal oscillations result from internal lee waves with 30 m vertical wavelength generated by the prevailing currents over the supercritical seamount flanks, whereby the bottom slope is greater than the internal tide wave slope. The ‘near-N’ waves are due to enhanced shear associated with the hydraulic jumps that form from the lee waves due to the abrupt transition from steeply sloping sides to a relatively flat summit. The jumps manifest themselves as bottom-trapped bores that propagate up the slope towards the summit. Further observations over the summit reveal that the bores subsequently flush the summits with cold water with tidal periodicity. The bores, which have long wave phase speeds more than double that of the bore particle velocities, are characterised by intense vertical velocities (>0.1 m s-1) and inferred local resuspension but relatively little turbulence based on temperature overturns. Our results strongly implicate lee waves as the dynamic mechanism of leading order importance to the previously observed accumulation of biomass adjacent to the supercritical slopes that are commonplace throughout the archipelago. We propose that further investigation should identify the spatiotemporal correlation between internal wave activity and fish schooling around the summit, and whether such schooling attracts predators.
    Keywords biomass ; Carcharhinus ; cold ; periodicity ; predators ; seamounts ; sharks ; temperature ; tides ; turbulent flow ; water ; wavelengths ; Indian Ocean
    Language English
    Dates of publication 2019-0122
    Size p. .
    Publishing place Elsevier Ltd
    Document type Article
    Note Pre-press version
    ISSN 0079-6611
    DOI 10.1016/j.pocean.2019.01.010
    Database NAL-Catalogue (AGRICOLA)

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