Ecosystem Analysis - World wide comparisons
Seasonal benthic nutrient fluxes in selected hydrodynamically different estuaries of the Eastern Cape, South Africa, and the Sylt-Rømø Bight in the German Wadden Sea
The ecological functioning of estuaries and other types shallow coastal ecosystems depends largely on physical processes (e.g. tidal pulsing, river flow, mixing, and general hydrodynamic features such as currents, stratification, flushing times), the chemical characteristics (e.g. salinity, marine and freshwater, groundwater inflow) and biogeochemical processes (regeneration, recycling, benthic-pelagic coupling, utilization of nutrients). The cycling of nutrients, in particular, has a profound influence on biological processes such as primary and secondary production, physiological behaviour and adaptations of living organisms. In a joint Ph.D. study between the University of Port Elizabeth, South Africa, and the Alfred Wegener Institute, nutrient fluxes in a selection of hydrodynamically different coastal ecosystems (various hydrodynamically different estuaries in the Eastern Cape, South Africa, and the Sylt-Rømø Bay, Wadden Sea, German North Sea) are measured by means of the bell jar incubation method (see picture). By means of these benthic bell jars, nutrient fluxes between the sediment and the water column can be measured in a specific community.
It has long been established that the activities (e.g. physiology, behaviour) of organisms either directly or indirectly influence estuarine biogeochemical processes. For example, estuarine flora may influence biogeochemical processes directly by taking up or releasing nutrients, or indirectly with photosynthesis/respiration. Alternatively, estuarine fauna may influence biogeochemical processes with burrowing activity (bioirrigation), excretion, filtration, or the production of faecal pellets. These activities, and their rates will vary between diverse types of estuarine and coastal systems depending on the floral/faunal communities present and their physiological/behavioural condition. A direct comparison of diverse estuarine and shallow coastal systems will lead to a better understanding of the function and behaviour of various coastal ecosystems on a global scale, which, in turn, leads to improved management strategies and conservation of these unique ecosystems.