"Eutrophication of estuarine and coastal ecosystems due to increased anthropogenic inputs of nitrogen is an increasing problem. Benthic microbial processes can in part alleviate this by removing a significant part of the load. Nitrate in marine sediments can be removed by two main functional groups of bacteria. Bacterial denitrifiers reduce nitrate or nitrite to gases subsequently lost from the aquatic environment, while nitrate ammonifiers reduce nitrate to ammonium that remains in the system. In addition, a novel process, anammox can also remove significant amounts of N in certain environments. However, a product of denitrification is the greenhouse gas nitrous oxide. Understanding the benthic processes involved in the removal of nitrogen, or the formation of nitrous oxide, is important for the management and reduction of nutrient load to coastal waters and greenhouse gases emissions. Although denitrification has been studied extensively, the other two processes and the factors that regulate the competition between these groups of bacteria remain largely unknown. Objectives of the project is to (1) link the distribution of gene abundance coding for key enzymes in the benthic nitrate reducing community and relate these to process rates and (2) study the environmental factors that influence the competition between the different functional groups of nitrate reducing bacteria. To accomplish this, we will apply modern molecular (eg. real time PCR) and biogeochemical (eg. stable isotopes, microelectrodes) techniques in an interdisciplinary way. The results will allow to test the hypotheses that changes in the availability of electron acceptors and donors result in differences in the distribution of functional genes and groups of nitrate reducers and that differences in rates and relative importance of key nitrogen processes along an estuarine gradient are related with changes in the expression of the corresponding functional genes."