Key parameters and processes affecting the re-establishment of eelgrass in estuaries and coastal waters (REELGRASS)
Founded by The Danish Strategic Research Council
The last 10-15 years effort to reduce the nutrient loading is now paying off as reduced pelagic nutrient levels and primary production. As a consequence, the light climate has improved and light now reaches sediments that were in the dark some years ago. Coastal managers have therefore expected that eelgrass should reestablish its coverage according to the new light conditions. This has not happened and although much effort has been spent to elucidate the lacking reestablishment, our understanding of the dominating processes and mechanisms of recolonization is still limited. Most research activities within the last years have focused on studies of factors affecting mortality of eelgrass. We want to examine the problem from another point of view. Our hypothesis is that processes involved in the recolonization of eelgrass are different from those affecting eelgrass mortality and decline in coverage. In this project we will spatially and temporally link observations of eelgrass recolonization and lack thereof with studies of physical, chemical and biological factors related to sediments. These include current and wave induces stress, cohesive behavior of sediments, degradation and history of the sediment organic pools, sediment biogeochemical processes and ben-thic fauna biomixing and grazing processes. These studies will be conducted in the field, and survey stations will be chosen in areas where eelgrass potentially should have recolonized and in areas where they are re-established. These surveys will be combined with a suite of laboratory flume studies where sediment conditions, physical stress, light intensity, temperature, oxygen and nutrient conditions will be kept under strict control. The intention is that the results of this project improve the currently insufficient dynamic models to simulate potential recolonization areas. With the implementation of the EU Water Frame Directive, eelgrass will be a key indicator for the evaluation of the water quality in estuaries. Our studies aim to provide the needed information and knowledge for a successful use of eelgrass as a water quality and habitat indicator.