Erik Krogh Kristensen

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The present paper reviews the current knowledge on diagenetic carbon transformations at the oxic/anoxic interface in coastal marine sediments. Oxygen microelectrodes have revealed that most coastal sediments are covered only by a thin oxic surface layer. The penetration depth of oxygen into sediments is controlled by the balance between downward transport(More)
Anaerobic mineralization processes were studied over a period of 40 d in an organic-rich sediment amended with labile organic matter (fish food pellets). Although measured sulfate reduction rates (SRR) were hlgh (up to -2400 nmol cm-3 d-l), a coexistence between sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) was evident. Methane(More)
The influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, iron, and sulfur biogeochemistry in mangrove sediment was studied using outdoor mesocosms with and without plants (21 m22) and crabs (68 m22). Saplings grew more leaves and pneumatophores in the presence of crabs. Dense microalgal mats lead to two to six times(More)
Known effects of bioturbation by common polychaetes (Nereis spp. and Arenicola marina) in Northern European coastal waters on sediment carbon diagenesis is summarized and assessed. The physical impact of irrigation and reworking activity of the involved polychaete species is evaluated and related to their basic biology. Based on past and present(More)
Dimensionless ammonium adsorption coefficients (K) were determined for tropical mangrove forest sediments and temperate Wadden Sea sediments. The K values were obtained from ammonium adsorption isotherms of KCl (2 M) extractable ammonium versus dissolved ammonium in the porewater; relationships that can be described by a linear model. Linearity was evident(More)
Oxygen concentration was measured in aerial roots (pneumatophores), horizontal cable roots and surrounding sediment of the tree Avicennia marina (Forsk.) Vierh. in a mangrove swamp at Ao Nam Bor, on the southeast coast of Phuket Island, Thailand. The O2 measurements were made in the field with a polarographlc oxygen minielectrode. The O2 concentration(More)
Nutrient release from the sediments in shallow eutrophic estuaries may counteract reductions of the external nutrient load and prevent or prolong ecosystem recovery. The magnitude and temporal dynamics of this potential source, termed internal nutrient loading, is poorly understood. We quantified the internal nutrient loading driven by microbial(More)
Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand. Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and seagrass beds in front of the mangrove forest. Benthic processes (O2 and CO2 fluxes) and nutrient dynamics(More)
Central aspects of carbon and sulfur biogeochemistry were studied along a transect extending from an unvegetated mudflat into a Spartina anglica salt marsh. Conditions along the transect differed with respect to tidal elevation, sediment characteristics, vegetation coverage, and benthic macrofauna abundance. Dark sediment O2 uptake and CO2 emission at the(More)