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The Wadden Sea squeeze as a cause of decreasing sedimentary organic loading
Delafontaine, M.T.; Flemming, B.W.; Mai, S. (2000). The Wadden Sea squeeze as a cause of decreasing sedimentary organic loading, in: Flemming, B.W. et al. (Ed.) Muddy coast dynamics and resource management. Proceedings in Marine Science, 2: pp. 273-286
In: Flemming, B.W.; Delafontaine, M.T.; Liebezeit, G. (Ed.) (2000). Muddy coast dynamics and resource management. Proceedings in Marine Science, 2. Elsevier: Amsterdam. ISBN 0-444-50464-8. 294 pp., more
In: Proceedings in Marine Science. Elsevier: New York. ISSN 1568-2692, more
Peer reviewed article  

Available in  Authors 
    VLIZ: Dynamical Oceanography [6357]

Authors  Top 
  • Delafontaine, M.T.
  • Flemming, B.W.
  • Mai, S.

Abstract
    In this study the inventories of mud and organic matter in the surficial sediments of two East Frisian tidal basins are compared with those known to have existed in adjacent intertidal flats removed by land reclamation. Based on a dense sample grid (>3000 samples), the average contents of particulate organic carbon (POC) were found to be 0.106% in the sand fractions, 2% in the mud fractions of the muddy sands on the dike flats (5-40% mud content), and 4.5% in the mud fractions of the very slightly muddy sands on the island flats (<5% mud content). Using an empirically derived dry bulk density relationship, the masses of mud and POC were determined for the surficial sediments (upper 5 cm) of the modern tidal flats in the two basins. Thus, at the time of the survey, the total mud mass in the upper 5 cm of the Langeoog tidal basin (90 km²) amounted to 0.313 x 106 tonnes and the POC mass to >6000 tonnes, whereas in the Spiekeroog tidal basin (74 km²) the mud mass mounted to 0.4 x 106 tonnes and the POC mass to >8000 tonnes. The reconstructed tidal flats were found to consist of some mixed flats (ca. 60 km²) and larger expanses of pure mud flats (ca. 160 km²). Using the same empirical dry bulk density relationship, the highest concentrations (masses per unit volume) of mud and POC were found to occur in a belt of sandy mud with a mean mud content of about 60%. At higher mud contents (60-100% mud) the respective masses decreased again due to increasing water contents and associated lower dry bulk densities. Based on these constraints, a total mass of ca. 1.38 x 106 tonnes of mud and 26,400 tonnes of POC was estimated to have existed in the reconstructed tidal flats of the Langeoog tidal basin, and 2.08 x 106 tonnes of mud and 36,800 tonnes of POC in the reconstructed tidal flats of the Spiekeroog tidal basin. The mud and POC lost by land reclamation thus exceed those of the modern tidal basins by a factor of about 4.4 and 5.2 (for mud), and 4.4 and 4.6 (for POC), respectively. We conclude that the man-induced Wadden Sea squeeze has resulted in a substantial decrease in the total loads of fine-grained material and organic matter (and pollutants, for that matter) in the modern back-barrier tidal flats. A further loss mud and organic matter is predicted in the course of continued sea-level rise.

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