Stability Properties in the Wadden Sea

Grimm, Volker; Bietz, Hauke; Günther, Carmen-Pia; Hild, Andreas; Villbrandt, Marlies; Niesel, Verena; Schleier, Ulrike; Dittmann, Sabine

doi:10.1007/978-3-642-60097-5_9

Cited by 3 publications

(1 citation statement)

References 34 publications

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“…The Wadden Sea at the southeastern edge of the North Sea covers one of the worlds largest tidal flat areas. Confined by a meso-tidal barrier island chain with intermittent estuaries of major river systems, the wide siliciclastic back barrier tidal flats host a rather resilient ecosystem in the midst of a densely populated and highly industrialized region (Hertweck, 1994;Ducrotoy and Elliott, 1997;Kock, 1998;Grimm et al, 1999).…”

Section: The Transgressive Barrier Island Depositional Systemmentioning

confidence: 99%

On the origin of highly active biogeochemistry in deeper coastal sediments – inverse model studies

Holstein¹,

Wirtz²,

Wirz³

2010

Preprint

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Abstract. In coastal sediments, zones with highly active diagenesis may be situated below the usually studied first decimeters. Pore water profiles from a backbarrier tidal flat in the German Wadden Sea display a SO4 minimum zone associated with a distinct NH4 peak at a sediment depth of around 1.5 m. Such evidence for significant degradation of organic matter (OM) is challenging our understanding of tidal flat biogeochemistry as little is known about processes that rapidly transfer reactive OM into layers far distant from the sediment-water interface. We here test and compare two different scenarios for OM transfer: scenario A assumes rapid sedimentation and burial of OM, scenario B assumes lateral advection of suspended POM. A diagenetic model is adapted to describe both hypotheses. Uncertain process parameters, in particular those connected to OM degradation and (vertical or lateral) transport are systematically calibrated using existing data. We found that both scenarios, advection and sedimentation, have solutions consistent with the observed pore water profiles. Constrained process parameters are within the range of reported values. Solutions to scenario B describing advective transport of particulate material are, however, rather improbable due to highly specific assumptions on the OM source and flow geometry. In the alternative deposition set-up, model simulations suggest that the source OM was deposited about 60 yrs earlier (1945). A mean sedimentation rate of approximately 2 cm yr−1 indicates substantial changes in near coast sediment morphology, since sea level rise is at a much lower pace. High sedimentation rates most probably reflect the progradation of flats within the study area. These or similar morphodynamic features also occur in other coastal areas so that regional values for OM remineralization rates may often be much higher than predicted from surface biogeochemistry.

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Section: The Transgressive Barrier Island Depositional Systemmentioning

confidence: 99%

On the origin of highly active biogeochemistry in deeper coastal sediments – inverse model studies

Holstein¹,

Wirtz²,

Wirz³

2010

Preprint

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Back¹,

Türkay²

2001

Ethics of Science and Technology Assessment

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Organic matter accumulation and degradation in subsurface coastal sediments: a model-based comparison of rapid sedimentation and aquifer transport

Holstein

Wirtz²

2010

Biogeosciences

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Abstract. The redox succession in shallow marine sediments generally exhibits a predictable pattern. Pore water profiles from a back barrier tidal flat in the German Wadden Sea depart from the expected redox zoning. Instead, a sulfate minimum zone associated with a sulfate-methane-sulfate double interface and a distinct ammonium peak at 1.5 m below sea floor (mbsf) is displayed. Such evidence for significant degradation of organic matter (OM) in subsurface layers is challenging our understanding of tidal flat biogeochemistry as little is known about processes that relocate reactive OM into layers far distant from the sediment-water interface. The objectives of our model study were to identify possible mechanisms for the rapid transport of organic matter to subsurface layers that cause the reversed redox succession and to constrain several important biogeochemical control parameters. We compared two scenarios for OM transfer: rapid sedimentation and burial of OM as well as lateral advection of suspended POM. Using a diagenetic model, uncertain process parameters, in particular those connected to OM degradation and (vertical or lateral) transport, are systematically calibrated using field data.We found that both scenarios, advection and sedimentation, had solutions consistent with the observed pore water profiles. For this specific site, however, advective transport of particulate material had to be rejected since the reconstructed boundary conditions were rather improbable. In the alternative deposition set-up, model simulations suggested the deposition of the source OM about 60 yrs before cores Correspondence to: J. M. Holstein (j.holstein@icbm.de) were taken. A mean sedimentation rate of approximately 2 cmyr −1 indicates substantial changes in near coast tidal flat morphology, since sea level rise is at a much lower pace. High sedimentation rates most probably reflect the progradation of flats within the study area. These or similar morphodynamic features also occur in other coastal areas so that inverted redox succession by horizontal or vertical transport may be more common than previously thought. Consequently, regional values for OM remineralization rates may be higher than predicted from surface biogeochemistry.

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Stability Properties in the Wadden Sea

Cited by 3 publications

References 34 publications

On the origin of highly active biogeochemistry in deeper coastal sediments – inverse model studies

On the origin of highly active biogeochemistry in deeper coastal sediments – inverse model studies

Quantifizierungsmöglichkeiten der Biodiversität

Organic matter accumulation and degradation in subsurface coastal sediments: a model-based comparison of rapid sedimentation and aquifer transport

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