Temporal and spatial high resolution analysis of nutrient dynamics in the near bottom layer of the Wadden Sea: Methodological aspects and first results

A probe that allows to take water samples in intertidal areas at high spatial resolution in the first metre above the bottom without disturbing the current profile has been developed. Data on dissolved inorganic nutrients were obtained at a temporal resolution of 30 minutes and spatial distances of 2, 4, 8, 16, 32. 64 and 100 cm above the bottom from up to three hours before to up to four hours after high tide. The layer in direct contact with the sediment showed marked concentration changes with tidal state. All compounds analysed exhibited a pronounced minimum at or immediately after current direction change. Depth profiles, on the other hand, did not give such a consistent picture. Individual compounds showed fluxes into and out of the sediment independently of each other and of tidal state. The data state. The data obtained suggest that sediment-water interactions play a major role in controlling nutrient concentrations in intertidal waters on short time scales.