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Distributions and characteristics of dissolved organic matter in temperate coastal waters (Southern North Sea)
Andrea Lübben, Olaf Dellwig, Sandra Koch, Melanie Beck, Thomas H. Badewien, Sibylle Fischer and Rainer Reuter
and Rainer Reuter
Ocean Dynamics, Special Issue - WATT
Abstract
The spatial and temporal distributions of chromophoric dissolved organic
matter (CDOM) and dissolved organic carbon (DOC) was studied in the
East-Frisian Wadden Sea (Southern North Sea) during several cruises between
2002 and 2005. The spatial distribution of CDOM in the German Bight shows a
strong gradient towards the coast. Tidal and seasonal variations of dissolved
organic matter (DOM) identify freshwater discharge via flood-gates at the
coastline and pore water efflux from tidal flat sediments as the most
important CDOM sources within the backbarrier area of the Island of Spiekeroog.
However, the amount and pattern of CDOM and DOC is strongly affected by
various parameters, e.g. changes in the amount of terrestrial run-off,
precipitation, evaporation, biological activity and photooxidation. A
decoupling of CDOM and DOC, especially during periods of pronounced biological
activity (algae blooms and microbial activity), is observed in spring and
especially in summer. Mixing of the endmembers freshwater, pore water, and
open sea water results in the formation of a coastal transition zone. Whilst
an almost conservative behaviour during mixing is observed in winter, summer
data point towards non-conservative mixing.
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