Lateral transport controls distribution, quality, and burial of organic matter along continental slopes in high-productivity areas

Inthorn, Maik; Wagner, Thomas; Scheeder, Georg; Zabel, Matthias

doi:10.1130/g22153.1

Cited by 147 publications

(136 citation statements)

References 18 publications

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“…Sediments were collected from two stations during the RV Meteor cruise M76/1 (Zabel and Ferdelman, 2008), one on the shelf in 130 m water depth and one on the continental slope in 2000 m water depth. Sediments from the shelf and from the slope have high concentrations of organic carbon of up to 20 % dry weight that decrease to about 7-8 % in the depocenter on the continental slope (Inthorn et al, 2005). This decrease corresponds well with the decrease in sulfate reduction rates (SRR) with increasing water depth ( Table 2, Brüchert et al, 2003).…”

Section: Namibian Shelf and Slopementioning

confidence: 49%

“…Organic matter from the coastal Benguela upwelling system on the Namibia shelf undergoes continuous suspension and redeposition leading to a net downslope transport. The shelf material accumulates in depocenters at 1000-1500 m water depth, where the sediment is rich in organic matter (Inthorn et al, 2005(Inthorn et al, , 2006. The slope sediments off Uruguay and Argentina are also characterized by dynamic depositional conditions (Riedinger et al, 2005).…”

Section: Sediment Transport Effects On Experimentallydetermined Tempementioning

confidence: 99%

“…The bottom water temperatures of the Namibian shelf vary annually between 7 and 10 • C on the shelf and between 1 and 4 • C on the slope (Lass and Mohrholz, 2005). The shelf and slope system is characterized by seaward and downslope particle transport that maintains local high sedimentation rates in a depocenter at 1000-1500 m water depth (Inthorn et al, 2005). Sediments were collected from two stations during the RV Meteor cruise M76/1 (Zabel and Ferdelman, 2008), one on the shelf in 130 m water depth and one on the continental slope in 2000 m water depth.…”

Section: Namibian Shelf and Slopementioning

confidence: 99%

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Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

2012

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Abstract. The temperature responses of sulfate-reducing microbial communities were used as community temperature characteristics for their in situ temperature adaptation, their origin, and dispersal in the deep sea. Sediments were collected from a suite of coastal, continental shelf, and slope sediments from the southwest and southeast Atlantic and permanently cold Arctic fjords from water depths ranging from the intertidal zone to 4327 m. In situ temperatures ranged from 8 • C on the shelf to −1 • C in the Arctic. Temperature characteristics of the active sulfate-reducing community were determined in short-term incubations with 35 S-sulfate in a temperature gradient block spanning a temperature range from 0 to 40 • C. An optimum temperature (T opt ) between 27 • C and 30 • C for the South Atlantic shelf sediments and for the intertidal flat sediment from Svalbard was indicative of a psychrotolerant/mesophilic sulfate-reducing community, whereas T opt ≤ 20 • C in South Atlantic slope and Arctic shelf sediments suggested a predominantly psychrophilic community. High sulfate reduction rates (20-50 %) at in situ temperatures compared to those at T opt further support this interpretation and point to the importance of the ambient temperature regime for regulating the short-term temperature response of sulfate-reducing communities. A number of cold (< 4 • C) continental slope sediments showed broad temperature optima reaching as high as 30 • C, suggesting the additional presence of apparently mesophilic sulfate-reducing bacteria. Since the temperature characteristics of these mesophiles do not fit with the permanently cold deep-sea environment, we suggest that these mesophilic microorganisms are of allochthonous origin and transported to this site. It is likely that they were deposited along with the mass-flow movement of warmer shelf-derived sediment. These data therefore suggest that temperature response profiles of bacterial carbon mineralization processes can be used as community temperature characteristics, and that mixing of bacterial communities originating from diverse locations carrying different temperature characteristics needs to be taken into account to explain temperature response profiles of bacterial carbon mineralization processes in sediments.

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Section: Namibian Shelf and Slopementioning

confidence: 49%

Section: Sediment Transport Effects On Experimentallydetermined Tempementioning

confidence: 99%

Section: Namibian Shelf and Slopementioning

confidence: 99%

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Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

2012

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“…A further important contribution to the lateral transport of organic carbon is that of dissolved organic carbon (DOC), estimated to account for 20 % of the export to depth and for about 10 % of the respiration rates in the deep ocean (Hansell, 2002;Arístegui et al, 2002;Ducklow et al, 2001). As a consequence of these transport processes, the different organic carbon pools get redistributed laterally from regions of excess production to regions of intense remineralization and burial (Inthorn et al, 2006b;Hwang et al, 2008), giving rise to a complex three-dimensional pattern of organic carbon cycling.…”

Section: Introductionmentioning

confidence: 99%

On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

Lovecchio¹,

Gruber²,

Münnich³

et al. 2017

Biogeosciences

106

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Abstract. A compilation of measurements of net community production (NCP) in the upper waters of the eastern subtropical North Atlantic had suggested net heterotrophic conditions, purportedly supported by the lateral export of organic carbon from the adjacent, highly productive Canary Upwelling System (CanUS). Here, we quantify and assess this lateral export using the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. We employ a new Atlantic telescopic grid with a strong refinement towards the northwestern African shelf to combine an eddy-resolving resolution in the CanUS with a full Atlantic basin perspective. Our climatologically forced simulation reveals an intense offshore flux of organic carbon that transports about 19 Tg C yr −1 away from the nearshore 100 km over the whole CanUS, amounting to more than a third of the NCP in this region. The offshore transport extends beyond 1500 km into the subtropical North Atlantic, adding organic carbon along the way to the upper 100 m at rates of between 8 and 34 % of the alongshore average NCP as a function of offshore distance. Although the divergence of this lateral export of organic carbon enhances local respiration, the upper 100 m layer in our model remains net autotrophic in the entire eastern subtropical North Atlantic. However, the vertical export of this organic carbon and its subsequent remineralization at depth makes the vertically integrated NCP strongly negative throughout this region, with the exception of a narrow band along the northwestern African shelf. The magnitude and efficiency of the lateral export varies substantially between the different subregions. In particular, the central coast near Cape Blanc is particularly efficient in collecting organic carbon on the shelf and subsequently transporting it offshore. In this central subregion, the offshore transport adds as much organic carbon as nearly 60 % of the local NCP to the upper 100 m, giving rise to a sharp peak of offshore respiration that extends to the middle of the gyre. Our modeled offshore transport of organic carbon is likely a lower-bound estimate due to our lack of full consideration of the contribution of dissolved organic carbon and that of particulate organic carbon stemming from the resuspension of sediments. But even in the absence of these contributions, our results emphasize the fundamental role of the lateral redistribution of the organic carbon for the maintenance of the heterotrophic activity in the open sea.

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“…This phenomenon occurs in many areas in the ocean but most commonly along steep topographic relief (Sugai 1990;Isla et al 2004). Sediment focusing may greatly affect the dispersal and sequestration of organic matter (Inthorn et al 2006) and interpretation of the sedimentary record (Pondaven et al 2000;Francois et al 2004). …”

mentioning

confidence: 99%

Resuspension by fish facilitates the transport and redistribution of coastal sediments

Katz

Yahel

Reidenbach

et al. 2012

Limnology & Oceanography

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Oxygen availability restricts groundfish to the oxygenated, shallow margins of Saanich Inlet, an intermittently anoxic fjord in British Columbia, Canada. New and previously reported 210 Pb measurements in sediment cores compared with flux data from sediment traps indicate major focusing of sediments from the oxygenated margins to the anoxic basin seafloor. We present environmental and experimental evidence that groundfish activity in the margins is the major contributor to this focusing. Fine particles resuspended by groundfish are advected offshore by weak bottom currents, eventually settling in the anoxic basin. Transmittance and sediment trap data from the water column show that this transport process maintains an intermediate nepheloid layer (INL) in the center of the Inlet. This INL is located above the redox interface and is unrelated to water density shifts in the water column. We propose that this INL is shaped by the distribution of groundfish (as resuspension sources) along the slope and hence by oxygen availability to these fish. We support this conclusion with a conceptual model of the resuspension and offshore transport of sediment. This fish-induced transport mechanism for sediments is likely to enhance organic matter decomposition in oxygenated sediments and its sequestration in anoxic seafloors.

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Lateral transport controls distribution, quality, and burial of organic matter along continental slopes in high-productivity areas

Cited by 147 publications

References 18 publications

Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

Resuspension by fish facilitates the transport and redistribution of coastal sediments

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