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Coastal hypoxia and sediment biogeochemistry

Middelburg, J.J. and Levin, L.A. (2009) Coastal hypoxia and sediment biogeochemistry. Biogeosciences, 6, 1273-1293. ISSN 1726-4170.

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Official URL: http://dx.doi.org/10.5194/bg-6-1273-2009

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 bottom-water 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.

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:6181
Deposited On:23 Mar 2010 01:00
Last Modified:15 Jan 2014 09:18

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