Melanie Beck

Consistent assessment of trace metal contamination in surface sediments and suspended particulate matter: A case study from the Jade Bay in NW Germany

Recently, within the framework of European directives, the importance of marine monitoring programs has increased. In this study, a dense sampling grid was applied for a detailed assessment of the metal contents of surface sediments and suspended particulate matter from the Jade Bay, one of the tidal basins in the southern North Sea. The local lithogenic background was defined and compared with average shale, a common reference material. Based on the calculated non-lithogenic fraction and a cluster analysis, the metals are distributed in two groups: (i) elements of mainly natural origin (Co, Cr, and a major portion of Cd) and (ii) elements associated with anthropogenic activity (As, Cd, Cu, Ni, Pb, Sn, and Zn). However, even the metals of the second group are enriched by at most a factor of two relative to the local background, suggesting minimal anthropogenic impact. Spatial distribution maps show that the harbor area of Wilhelmshaven may be a particularly important source of metal.

Macrofauna communities of tidal channels in Jade Bay (German Wadden Sea): spatial patterns, relationships with environmental characteristics, and comparative aspects

The increasing impact of human activities, global warming, rising sea levels, and alien species invasion are major drivers of ecological changes in the benthic ecosystems of the Wadden Sea. Repeated benthological and sedimentological investigations have been conducted for intertidal flats, offshore regions, and estuaries. There is a gap in knowledge, however, with respect to the spatial distribution and structure of benthic communities in tidal channel systems of the Wadden Sea. In this study, the spatial distribution of subtidal macrofauna communities in relation to environmental variables in the lesser-known tidal channels of Jade Bay (Wadden Sea of Lower Saxony, southern North Sea) were investigated. In 2009, grab samples were taken at 29 stations, and a total of 98 macrofauna taxa were recorded, with polychaetes predominating. Distinct macrofauna communities among and within the tidal channels were identified using multivariate statistics. Distance-based linear models revealed that tidal current velocity and depth best explained the spatial variation in macrofauna community structure. On a smaller spatial scale, within the tidal channels, the relationships between macrofauna communities and sediment characteristics were greater. Oligochaete species (Tubificoides benedii, Tubificoides pseudogaster, Heterochaeta costata), Peringia ulvae, and polychaetes (Hediste diversicolor, Nephtys hombergii, Streblospio benedicti) showed the highest correlation with the multivariate abiotic data. In addition, species such as the anemone Urticina felina were found to benefit from the presence of hard substrates (patches of gravel), which highlights the importance of local habitat heterogeneity. A comparison among different subtidal basins in the Wadden Sea based on dominant macrofauna species revealed that the macrofauna community structure of Jade Bay showed the greatest similarity with communities of the western Dutch Wadden Sea. In contrast, the greatest dissimilarity was found between the Jade Bay and Sylt communities, likely attributable to differences in sedimentological and hydrodynamical characteristics.

Observatory in the Wadden Sea: Nutrient cycling and export to the North Sea

In the southern North Sea, an observatory is permanently installed in the tidal flat area of Spiekeroog Island. The observatory permits continuous nutrient (silica, phosphate, nitrate, nitrite) measurements in the open water column. Nutrients vary on tidal and seasonal time scales depending on phytoplankton dynamics and nutrient recycling in tidal flat sediments. Model results indicate that dissolved nutrients are exported from the tidal flat system to coastal waters of the North Sea. Thus, nutrient cycling in tidal flat areas may influence nutrient and phytoplankton dynamics in coastal waters of the southern North Sea.