Nutrient and carbon dynamics within the river-estuary-coastal water systems are key processes to understand the flux of matter from the terrestrial environment to the ocean. Here, we analysed those dynamics by following a sampling approach based on the travel time of water. We started with a sampling of River Elbe from the source. After a subsequent investigation of the estuary, we  followed the plume of the river by raster sampling the German Bight (North Sea) using three ships simultaneously. In the river, we detected intensive growth of phytoplankton connected with high oxygen saturation and pH values and undersaturation of CO2, whereas concentrations of dissolved nutrients declined. In the estuary, the Elbe shifted from an autotrophic to a heterotrophic system: Phytoplankton died off upstream of the salinity gradient causing minima in oxygen saturation and pH, supersaturation of CO2, and a release of nutrients. In the shelf region, phytoplankton and nutrient concentrations were low, oxygen close to saturation, and pH in a typical marine range. We detected a positive relationship between pH and oxygen saturation and a negative one between pCO2 and oxygen saturation. Flux rates of dissolved nutrients from river into estuary were low and determined by depleted concentrations. In contrast, fluxes from the estuary to the coastal waters were higher and the pattern was determined by tidal current. Overall, the approach is appropriate to better understand land-ocean fluxes, particularly if it is performed under different hydrological conditions including extremes.

Primary Presenter: Norbert Kamjunke, Helmholtz Centre for Environmental Research (norbert.kamjunke@ufz.de)

Authors:

Norbert Kamjunke, Helmholtz Centre for Environmental Research  (norbert.kamjunke@ufz.de)

Holger Brix,   ()

Götz Flöser,   ()

Ingeborg Bussmann,   ()

Claudia Schütze,   ()

Eric Achterberg,   ()

Tina Sanders,   ()

Vanessa Russnak,   ()

Anna Matousu,   ()

Petr Znachor,   ()

Markus Weitere,   ()