Role of a strong oxygen-deficient zone in the preservation and degradation of organic matter: a carbon budget for the continental margins of northwest Mexico and Washington State

Hartnett, Hilairy E.; Devol, Allan H.

doi:10.1016/s0016-7037(02)01076-1

Cited by 163 publications

(142 citation statements)

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“…4a). This dependence of sediment oxygen uptake on sediment oxygen concentrations has been observed on the Louisiana shelf (Rowe et al, 2002(Rowe et al, , 2008, in the Black Sea (Friedl et al, 1998) and along the ocean margin off Washington State and Mexico (Hartnett and Devol, 2003) although the overriding control of carbon deposition may mask oxygen dependencies. Moreover, an oxygen dependency is also consistent with global-scale empirical relations (Cai and Reimers, 1995) and theoretical predictions based on the simple models incorporating zero-order uptake kinetics and diffusive transport (Bouldin, 1968).…”

Section: The Effect Of Oxygen On Diagenetic Pathways and Sediment-watmentioning

confidence: 69%

Coastal hypoxia and sediment biogeochemistry

2009

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Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 µM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottomwater oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Section: The Effect Of Oxygen On Diagenetic Pathways and Sediment-watmentioning

confidence: 69%

Coastal hypoxia and sediment biogeochemistry

2009

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“…While the attenuation of the particle flux is well described by a power-law decrease with depth, with a weaker attenuation in OMZs compared with well-oxygenated waters (36)(37)(38), the depths at which migrators respire are more uncertain. The simplest assumption is that NH 4 + excretion peaks around the migration depth, and becomes quickly negligible below it.…”

Section: Dvm Effects On the N Cycle In Anoxic Watersmentioning

confidence: 99%

“…29, relies on the following assumptions. Particle export follows a power-law profile, with strong remineralization (exponent b = −0.9) in oxygenated waters, and weak remineralization (b = −0.4) in anoxic waters (36)(37)(38). The suboxic threshold is set at 5 mmol·m −3 .…”

Section: Spatial Models Of Dvm Amplification Of Anammoxmentioning

confidence: 99%

Enhancement of anammox by the excretion of diel vertical migrators

Bianchi

Babbin

Galbraith

2014

Proc. Natl. Acad. Sci. U.S.A.

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Measurements show that anaerobic ammonium oxidation with nitrite (anammox) is a major pathway of fixed nitrogen removal in the anoxic zones of the open ocean. Anammox requires a source of ammonium, which under anoxic conditions could be supplied by the breakdown of sinking organic matter via heterotrophic denitrification. However, at many locations where anammox is measured, denitrification rates are small or undetectable. Alternative sources of ammonium have been proposed to explain this paradox, for example through dissimilatory reduction of nitrate to ammonium and transport from anoxic sediments. However, the relevance of these sources in open-ocean anoxic zones is debated. Here, we bring to attention an additional source of ammonium, namely, the daytime excretion by zooplankton and micronekton migrating from the surface to anoxic waters. We use a synthesis of acoustic data to show that, where anoxic waters occur within the water column, most migrators spend the daytime within them. Although migrators export only a small fraction of primary production from the surface, they focus excretion within a confined depth range of anoxic water where particle input is small. Using a simple biogeochemical model, we suggest that, at those depths, the source of ammonium from organisms undergoing diel vertical migrations could exceed the release from particle remineralization, enhancing in situ anammox rates. The contribution of this previously overlooked process, and the numerous uncertainties surrounding it, call for further efforts to evaluate the role of animals in oxygen minimum zone biogeochemistry.anammox | denitrification | oxygen minimum zone | diel vertical migration W ater column oxygen minimum zones (OMZs), where oxygen concentrations plummet to submicromolar levels (1), are responsible for approximately one-third of the total removal of fixed nitrogen from the oceans (2, 3). Several processes mediated by specialized prokaryotes convert fixed inorganic nitrogen (NH 4 + , NO 2 − , and NO 3 − ) to N 2 in anoxic waters. Canonical denitrification, consisting of dissimilatory NO 3 − reduction to NO 2 − (DNRN) followed by the further oxidation of organic matter with NO 2 − (the denitrification step), was long considered the dominant fixed N removal pathway in anoxic waters. Over the last decade, anammox has gained attention as a major sink of fixed N in nearly anoxic waters (O 2 < 10 mmol·m −3 ) (4, 5).Stoichiometric considerations would suggest a close coupling between denitrification and anammox (6, 7). Under anoxic conditions, the NH 4 + liberated by the remineralization of organic matter through DNRN and denitrification should accumulate in the water column because conventional (aerobic) nitrification cannot proceed. However, this accumulation is not observed in the cores of anoxic waters, where observed NH 4 + concentrations are generally much less than 1 mmol·m −3 (8). In these regions, oxidation of NH 4 + with NO 2 − by anammox is thought to be the major sink of NH 4 + (9). Given that no significant NH 4 + acc...

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“…Microbial degradation has been observed to be slower under anoxic than under oxic conditions, though the difference is smaller for fresh, easily hydrolysable, than for more refractory substrates (Henrichs and Farrington, 1987;Lee, 1992;Sun et al, 1993;Harvey et 20 al., 1995;Kristensen et al, 1995;Sun et al, 1997;Lehmann et al, 2002). Oxygen deficient conditions have been shown to enhance organic carbon preservation, as an existing oxygen minimum zone (OMZ) in the water column allows a greater fraction of the export flux to reach the sediments and low bottom water oxygen concentrations decrease the efficiency of carbon oxidation in the sediment (Hartnett et al, 1998;Hartnett and Devol, 2003). 25…”

Section: Introductionmentioning

confidence: 99%

“…In the absence of dissolved oxygen, bacterial dissimilatory sulfate reduction is the quantitatively most important terminal electron acceptor process in most marine upwelling 5 sediments (Jørgensen, 1982;Canfield, 1989;Ferdelman et al, 1999;Hartnett and Devol, 2003). In sediments off central Chile (36°S), organic carbon mineralization rates determined by Thamdrup and Canfield (1996) indicated that sulfate reduction accounted for 100% of carbon oxidation in shelf sediments underlying oxygen-depleted bottom waters, and for at least 55% of carbon oxidation in slope sediments.…”

Section: Introductionmentioning

confidence: 99%

How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

Niggemann

Ferdelman

Lomstein

et al. 2007

Geochimica et Cosmochimica Acta

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. (2007) of autochthonous TOC and TIC, were higher at 36°S than at 23°S. We propose that sampling of isolated deposition centers, that collect particles originally distributed over a much wider 15 area led to unexpectedly high sediment accumulation rates in the northern area. Bioturbation was intense at 36°S even in sediments within the oxygen minimum zone, whereas there were no indications for sediment mixing at 23°S.

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Role of a strong oxygen-deficient zone in the preservation and degradation of organic matter: a carbon budget for the continental margins of northwest Mexico and Washington State

Cited by 163 publications

References 59 publications

Coastal hypoxia and sediment biogeochemistry

Coastal hypoxia and sediment biogeochemistry

Enhancement of anammox by the excretion of diel vertical migrators

How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

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