ELOISE is a European network for coastal zone research focusing on land-ocean interactions, and on how this is influenced by human activities. Operating since 1996, more than 50 ELOISE projects have been incorporated to the ELOISE cluster, rendering it the world’s largest coastal research initiative. ELOISE is intended to contribute directly to coastal zone management and spatial planning, and thus to European coastal policy. ELOISE has now entered a phase where scientific results have to be disseminated to all potential end-users in ministries to schools. All relevant ELOISE material is gathered in so called digests/themed overviews. The present document represents the NIOO (Netherlands Institute for Ecology) contribution as an overview on the ELOISE progress in knowledge on nutrient dynamics in European water systems.

Three mainstream topics were identified based on the up to date list of publications from the ELOISE projects:

1. Relating nutrient fluxes to land-based activities, atmospheric and river processes
2. Nutrient processing in estuaries and coastal areas – what processes govern the fate?
3. Effects of altered nutrient discharges on the functioning of coastal and estuarine foodwebs

Each of these topics is highlighted in the present document with original results published by members of ELOISE projects. Conclusions for each topics are summarized below:

ELOISE research has contributed significantly to a better understanding the human impacts on coastal ecosystems. Many processes highlighted by the ELOISE projects complicate this kind of representation enormously. For example, a consistent assessment of the effect of atmospheric deposition of nutrients on estuarine and coastal systems implies a requirement for modelling for at least nitrogen and phosphorus, on a  timescale of day, using a fine (20x20km) spatial grid dynamically coupled with outputs of meteorological models. However, tremendous progress has been observed in our understanding of the processes controlling the atmospheric deposition of nutrients on land and seas.

Outstanding developments have been realized in the modelling of nutrient fluxes from the watershed to the seas. The future certainly lies in the combination of both full deterministic and statistical approaches with particular attention to groundwater. Furthermore, progress is required for the coupling of the major macronutrients (N,P,Si) and organic matter with biological processes

Sediments play a central role in the transformation processes of nutrients brought to coastal areas. Whether sediment acts as sink or source of nutrients is closely dependent on biological processes. Much knowledge has been gathered on benthic nutrient fluxes that cannot be analytically solved with a single set of chemical equations. Current progress at the frontline of process modelling is developing the tools that will allow this integrative step.