The general aim of AMBER is the implementation and application of the Ecosystem Approach to Management (EAM) to the Baltic Sea in the face of two closely intertwined environmental threats, eutrophication and climate change. Focus is on the coastal ecosystem (CE) because it supports most of the 85 mi inhabitants of nine nations around the Baltic Sea catchment. The CE receives most human derived nutrient loads from rivers, submarine ground water discharge (SGD), atmospheric deposition, and point sources and links the land with the open Baltic Sea. The CE controls the biogeochemical transformations of P-, N- compounds (phosphate, nitrate, DON, etc.) through the close coupling between water and sediments. Furthermore, it is crucial for fish as reproduction area, nursery and grazing ground and tightly connected to the open Baltic Sea. For an optimal integrated management, the implementation and application of EAM concepts on the CE it is necessary to study in a holistic approach the link between the catchment (including groundwater) and the open Baltic Sea and how climate change will affect the river water constituents and the biogeochemistry of the coastal waters and sediments. Unfortunately it is difficult to separate the signals of climate change from the direct impact of human activity. To understand and manage the future development of CE, the separation of these signals is necessary. Hence, one of the first steps of AMBER is the separation of climate from anthropogenic signals by means of a combinatorial variation in model’s boundary conditions using the output of existing regional climate change scenarios and the output of a watershed model simulating changes in land use.

  

We propose to investigate the influence of changing pH and carbon dioxide partial pressure, and alkalinity on carbonate dissolution in surface sediments of the Wadden Sea and the consequences for and relation to the carbonate system of the North Sea. Our hypothesis is that biogenic carbonates at the surface of intertidal sediments and the upper sediment layers play -to different extents- a role in modifying tidal waters that exchange with the shallow North Sea. This adds to carbonate fluxes caused by benthic organic matter degradation. The absolute and relative importances will change as the North Sea carbonate system will acidify in the future. One important aspect will be the reactivity (reaction rates and thermodynamic stability) of different biogenic carbonates and the experimental quantification of the different dissolution rates in pure and seawater media under different controlled laboratory conditions, i.e. pH, partial pressure of carbon dioxide (PCO2-stat and free-drift), and carbonate undersaturation. The reactive surface of the carbonate will be characterized to extract specific dissolution rates from experimental data on the development of liberated major minor and trace cations and the dissolved carbonate species. Experiments will be carried out at different fixed CO2 partial. This approach will include in parallel experiments geomicrobiological effects on microbial degradation of the organic matrix compared to purely abiotic reactions. Experimental laboratory-based approaches will be compared to field in-situ transformation experiments and will be followed by microscopic (e.g., SEM-EDX), inorganic geochemical (ICP-OES, photometry, microsensors) and stable isotope (C, O; irmMS) approaches. Experiments will also be carried out in collaboration with Dr. Hoppema (3.2.3) regarding benthic mesocosm experiments at AWI. Field work will additionally characterize the sources and surface textures of different carbonate fractions in surface sediments with geochemical methods and SEM-EDX. These results will allow to evaluate the time-dependent corrosion of biogenic carbonates as a function of burial time. Application of microsensors to characterize the chemical gradients will be carried out in collaboration with Dr. D. deBeer (MPI-MM; 3.2.2). From the side of carbonate formation, the influence of a changed carbonate system on growth of Mytilus and Crassostrea is planned to be assessed in a later phase of the project. Finally, pelagic measurements and experimental results will link the alkalinity and DIC exchange with the coastal North Sea and the possible ecosystem consequences via biogeochemical modelling. Parameters of the dissolved carbonate system (TA, DIC, PCO2, pH) will be measured in collaboration with PD Dr. Bernd Schneider (IOW) while d13C(DIC) will be determined via irmMS. These results will be provided for a collaborative integration in Theme 5 (Pätsch et al.) and the inclusion in the modelling of the North Sea carbonate system. The approach provides the base for a quantitative understanding of the role of the carbonate system in the water column on preservation, destruction and temporal authigenesis in the intertidal surface sediments, and the role of benthic metabolisms.

  

 

Der Beibu Golf im südchinesischen Meer spielt eine wichtige Rolle für das Verständnis der natürlich und anthropogen induzierter Änderungen der Ablagerungsbedingungen subrezenter Sedimente und die Bilanz aus küstennahem Stoff-Eintrag, oberflächennahem Abbau von organischem Material, und dadurch induzierter Element-Flüsse. Es ist in diesem Teilprojekt vorgesehen, gemeinsam mit der Sektion Meereschemie anhand von biogeochemischen Untersuchungen von Wassersäule, Schwebstoffen, Sediment und Porenwässern Beiträge zum Verständnis der Quellen, Senken und Transformationen von organischem Material, organischer Kontaminanten und ausgewählter metallischer Spurenstoffe zu liefern. Die modellierende Analyse der Porenwässer soll Transformationsraten und die sensiblen Element-Flüsse über die Sediment-Wasser-Grenzschicht hinweg quantifizierbar machen. Auf zwei Expeditionen sollen im Feld Daten erhoben und die Wassersäule sowie die Sedimente beprobt werden. Die Probenahme während der ersten Ausfahrt erfolgt mit einem chinesischen Forschungsschiff zu Beginn des beantragten Forschungsprojektes. Darauf aufbauend ist vorgesehen, in der zweiten Phase mit dem deutschen FS SONNE anhand von Nord-Süd und Ost-West-Transekten die laterale biogeochemische Variabilität der Oberflächensedimente und ihre Konsequenz für die benthischen Transformationsleistungen und daraus resultierenden Stoffflüsse zu erfassen. Die Synthese dieser Daten soll es ermöglichen die hauptsächlich bestimmenden Rahmenbedingungen für die geochemische Zusammensetzung der sub-rezenten Sedimente sowie die Konsequenzen für die biogeochemisch benthisch-pelagischen Kopplung zu erfassen und mit anderen Küstenstandorten vergleichbar zu machen.