Impact of Thiomargarita on the rates of N, S and P turnover in mudbelt sediments from the Benguela Upwelling System: a model study

The availability of major nutrients, nitrogen (N) and phosphorus (P), largely controls primary productivity in eastern boundary upwelling systems. The oxygen minimum zone (OMZ) on the Namibian shelf is characterized by high productivity and extraordinarily high particulate organic carbon (POC) contents (up to 19 % dry weight) in the surface sediments. The anaerobic degradation of POC by bacterial sulfate reduction leads to the production of hydrogen sulfide (H2S) that supports extensive communities of large sulfur bacteria Thiomargarita namibiensis in surface shelf sediments. These bacteria oxidize sulfide by reducing nitrate (NO3-) to either ammonium (NH4+) or dinitrogen (N2). Thiomargarita also affect phosphorus cycling by intracellular incorporation of polyphosphates and extracellular formation of hydroxyapatites. In order to understand and quantify the complexity of the coupled benthic cycles of C, N, P, S, Fe in the Benguela Upwelling System, a reaction-transport model (RTM) was used to simulate sediment biogeochemical data collected from the RV Meteor cruise (M157, August 4th-September 16th 2019) off Namibia. This allowed deeper insights into the role of sulfur-oxidizing bacteria on P and N fluxes across the sediment surface. Results are presented that point toward potentially strong feedbacks by Thiomargarita on primary production in response to ongoing global warming and ocean deoxygenation.

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Carbon pathways and export associated with the southern Benguela upwelling system: a re-appraisal

South African Journal of Marine Science ◽

10.2989/025776198784126854 ◽

1998 ◽

Vol 19 (1) ◽

pp. 113-118 ◽

Cited By ~ 6

Author(s):

H. N. Waldron ◽

T. A. Probyn ◽

G. B. Brundri

Keyword(s):

Upwelling System ◽

System A ◽

Benguela Upwelling ◽

Carbon Pathways

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Modeling the primary and secondary productions of the southern Benguela upwelling system: A comparative study through two biogeochemical models

Global Biogeochemical Cycles ◽

10.1029/2004gb002427 ◽

2005 ◽

Vol 19 (4) ◽

pp. n/a-n/a ◽

Cited By ~ 46

Author(s):

V. Koné ◽

E. Machu ◽

P. Penven ◽

V. Andersen ◽

V. Garçon ◽

...

Keyword(s):

Comparative Study ◽

Upwelling System ◽

System A ◽

Biogeochemical Models ◽

Benguela Upwelling

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Presence of 236U and 237Np in a marine ecosystem: The northern Benguela Upwelling System, a case study

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.135222 ◽

2020 ◽

Vol 708 ◽

pp. 135222 ◽

Cited By ~ 3

Author(s):

Mercedes López-Lora ◽

Elena Chamizo ◽

Martina Rožmarić ◽

Deon C. Louw

Keyword(s):

Marine Ecosystem ◽

Upwelling System ◽

System A ◽

Benguela Upwelling

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Short-term variability during an anchor station study in the southern Benguela upwelling system: A simulation model

Progress In Oceanography ◽

10.1016/0079-6611(91)90023-f ◽

1991 ◽

Vol 28 (1-2) ◽

pp. 121-152 ◽

Cited By ~ 15

Author(s):

K.L. Cochrane ◽

A.G. James ◽

B.A. Mitchell-Innes ◽

G.C. Pitcher ◽

H.M. Verheye ◽

...

Keyword(s):

Simulation Model ◽

Short Term ◽

Anchor Station ◽

Upwelling System ◽

System A ◽

Benguela Upwelling ◽

Short Term Variability

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Coupled benthic cycling of iron, phosphorus and sulfur in the Benguela upwelling system

10.5194/egusphere-egu2020-19291 ◽

2020 ◽

Author(s):

Kristin Anna Ungerhofer ◽

Gert-Jan Reichart ◽

Peter Kraal

Keyword(s):

Water Column ◽

Bottom Water ◽

Solid Phase ◽

Oxygen Depletion ◽

Biogeochemical Cycles ◽

Sediment Surface ◽

Upwelling System ◽

Benguela Upwelling ◽

Bottom Waters ◽

The Impact

The Benguela upwelling system (BUS) offshore Namibia is among the most productive ocean regions worldwide and is a globally important reservoir of biodiversity and biomass. The forcing of cold, nutrient-rich deep waters up the coastal shelf leads to high rates of primary productivity in surface waters, intense carbon remineralization and consequently to (bottom water) oxygen depletion on the shelf that varies temporally and spatially with the intensity of the upwelling. Recurring events of deoxygenation have a severe impact on marine ecosystems, for instance increased mortality and altered biogeochemical cycles of key elements such as carbon (C), iron (Fe), phosphorus (P) and sulfur (S). Therefore, it is crucial that we establish a clear mechanistic framework of the impact of oxygen depletion on (global) biogeochemical cycles, not only to allow for the reconstruction of climate-ocean feedbacks in upwelling regions in the past, but to enable predictions of future behavior. During an expedition with RV Pelagia in February of 2019, we collected water column and sediment samples from the shelf and slope off Namibia (100 to 1517 m water depth, bottom water O2 between 0.5 and 175 &#181;mol L-1) and measured nutrient fluxes in on-board sediment incubations to understand the early diagenetic behavior of those key elements and trace metals underlying the (periodically) oxygen-depleted waters of the BUS. We analyzed dissolved concentrations as well as solid-phase speciation of key elements such as iron (Fe), manganese (Mn), phosphorus (P) and sulfur (S) to understand the chemical and physical processes controlling their distribution along the depth/redox-transect. Our results show intense P cycling on the shelf, as evidenced by very high pore-water P concentrations, an enhanced efflux of PO4 to suboxic bottom waters and indications of phosphorite formation at depth in the sediment. N/P ratios well below Redfield indicate N depletion and (relative) P accumulation in the water column, a shift in nutrient stoichiometry that can impact the composition of microbial communities in such waters. Meanwhile, the slope sediments are overlain by oxic bottom waters, retain P more efficiently and exhibit N/P ratios close to Redfield stoichiometry. The capacity of the sediment to buffer toxic sulfide and prevent its release to the water column was dependent on the abundance of sulfide oxidizers at the sediment surface. Furthermore, the variable accumulation of sulfide affected Fe speciation and sedimentary P retention. Overall, we show an intimate coupling between sedimentary cycles of essential elements in the Benguela upwelling system, a stark contrast between shelf and slope environments that is further enhanced by local variation of oxygen depletion and a very strong role of microbes in driving the cycles.

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Disentangling oxygen depletion in the Benguela Upwelling System: A biophysical approach.

10.5194/egusphere-egu2020-21909 ◽

2020 ◽

Author(s):

Natalia Herran ◽

Martin Schmidt

Keyword(s):

Water Column ◽

Ecological Model ◽

Regional Scale ◽

Sediment Resuspension ◽

Oxygen Depletion ◽

Chain Reactions ◽

Upwelling System ◽

System A ◽

Benguela Upwelling ◽

Biophysical Approach

Understanding the multilevel complexity of marine ecosystems is one of the greatest challenges on ecosystem modeling so far, due to the dualism of governing hydrodynamical processes acting on a regional scale and complex biogeochemical chain reactions that happen locally on the marine environment. A coupled hydrodynamic-ecological model based on nitrogen stoichiometry has been developed to better understand the short-term nutrient and oxygen coastal dynamics in the Benguela Upwelling System (BUS). The model shows that the effect of internal waves in the Benguela region re-shapes the benthic ecosystem due to the increased of turbulence on the ocean floor with a consequently increase of fine sediment on the water column. We show that an increase on organic-rich sediment resuspension on the water column enhance oxygen consumption and ultimately contribute to the apparent deoxygenation of the Namibian coastal shelf.

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Predatory species left stranded following the collapse of the sardine Sardinops sagax (Pappe, 1854) stock off the northern Benguela upwelling system: A review

Journal of Marine Systems ◽

10.1016/j.jmarsys.2021.103623 ◽

2021 ◽

pp. 103623

Author(s):

Victoria Ndinelago Erasmus ◽

Bronwen Currie ◽

Jean-Paul Roux ◽

Simon H. Elwen ◽

Moses Kalola ◽

...

Keyword(s):

Upwelling System ◽

System A ◽

Benguela Upwelling ◽

Sardinops Sagax

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Productivity of the forage of perennial grasses and their mixtures on drained peatlands

Interdepartmental thematic scientific collection "Agriculture" ◽

10.31073/zem.91.74-79 ◽

2016 ◽

Vol 2 (91) ◽

pp. 74-79

Author(s):

V.H. Kurhak ◽

M.I. Shtakal ◽

V.M. Shtakal

Keyword(s):

Dactylis Glomerata ◽

Dry Weight ◽

Phleum Pratense ◽

Bromus Inermis ◽

Metabolizable Energy ◽

Perennial Grasses ◽

Forest Steppe ◽

Left Bank ◽

Peat Soils ◽

High Productivity

There showed the productivity, chemical composition of feed and the timing of mowing of grass and variety mixes of permanent grasses on drained peat soils of Left Bank Forest-Steppe of Ukraine. The presence of early rip ened seeded grass provides a uniform supply use mowed mass from middle May until the end of September and the productivity of lands, which ranges from 10 to 14 t/ha of dry weight, metabolizable energy – 100.0 – 130.0 GJ and feed units 7-11 t/ha. Additional manuring of N90 on the background Р45К120 is effective at the start of second year of use. On the organization of hay conveyors of different ripening time herbages is possible to extend the optimal tim ing of mowing of green mass to 25-35 days. Best among the early-maturing grass crops are Dactylis glomerata va riety Kyivska rannia-1 with Alopecurus pratensis variety Sarnenskiy ranniy or its mixture with Bromus inermis and Festuca pratensis. With medium ripening – pure sowing eastern fescue of variety Lyudmila, Phalaris arundinacea variety Sarnenski-40, Bromus inermis variety Arsen and their compounds. High productivity of late-ripening herb age is provided by the inclusion in the composition of grass mixtures of Phleum pratense L. variety Vyshgorodska and Dactylis glomerata of variety Ukrainka, and Agrostis gigantea Roth variety Sarnenska piznia. It is also possible organization hay conveyors of different ripening varieties of Dactylis glomerata varieties Kyivska rannia, Muravka, Ukrainka.

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