Research

M. Lunau, A. Lemke, O. Dellwig, M. Simon

Tidal dynamics affect the linkage between hydrodynamic, geochemical and microbial processes

Tidally affected coastal ecosystems are characterized by strong hydrodynamic forcing, a high load of suspended particulate matter (SPM) and intense heterotrophic microbial processes which undergo rapid short-term changes. Despite many studies of these individual processes little is known about how hydrodynamics affect interactions between POC, DOC, bacterial growth and decomposition processes, mainly because of inappropriate sampling devices. Therefore, we studied SPM properties (aggregate size and abundance, POC, PON, chlorophyll, amino acids (AA)), DOC, dissolved AA, abundance and biomass production of free-living (FL) and SPM-associated bacteria during various seasonal situations in the German Wadden Sea. The results show distinct repetitive patterns of tidal currents, properties of SPM and the dissolved phase and bacterial abundance and biomass production. The incoming and outgoing tides have different impacts on dynamics of the measured parameters, in particular on short-term interactions between abundances and activities of FL- and SPM-associated bacteria. The abundance of FL-bacteria was inversely related to that of SPM-associated bacteria but covaried with concentrations of particulate combined AA. During phases of high current velocities, numbers of SPM-associated bacteria covaried with concentrations of dissolved AA.