In 1983 the first specimens of the North American spionid polychaete Marenzelleria viridis were found along the European mainland shore in the Ems estuary. Since then, this polychaete has spread over several estuaries around the North Sea and the Baltic. In the inner part of the Ems estuary juveniles were predominantly present in muddy sediments high in the intertidal zone; in more sandy sediments at higher salinities juveniles and adults co-occured. Detailed information was obtained at a muddy and at a sandy station.Gametes were present in the coelomic fluid from November through March. In May new recruits were found in the sediment samples, reaching densities of over 105 m -2 at the muddy station, and c. 2000 m -2 at the sandy station. During summer, densities decreased at the muddy station, coinciding with a density increase at the sandy station, suggesting migration of juveniles from a nursery to the adult habitat. Cage experiments showed that the decrease of juveniles at the muddy station could be attributed to migration and not to mortality due to predation.At the sandy habitat palps and anterior parts of M. viridis made up 4-11% of the stomach content of juvenile plaice (Pleuronectes platessa). In juvenile flounder (Platichthys flesus) only in April c. 10% of the stomach content consisted of M. viridis. During 1983During -1990 increasing densities of M. viridis at the sandy habitat coincided with a reduced abundance of Nereis diversicolor, however, this inverse relationship was not found to be statistically significant. Density fluctuations of M. viridis and Corophiurn volutator showed a significant positive relationship, the cause of which is not yet understood.

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The distribution of 0‐group flatfish was investigated in 1992 in the Dollard (Ems–Dollard estuary, Wadden Sea). 0‐Group plaice, flounder and sole were not evenly distributed over the sampled locations. The spatial distribution pattern of 0‐group flatfish in the Dollard changed during the investigation period. In the first week of sole presence, when the mean length of sole was 24–30 mm, salinity correlated significantly with sole density. The distribution of juvenile sole larger than 40 mm total length was affected by the elevation of the location: 0‐group sole was restricted to the sampled site with the lowest elevation. The distribution of 0‐group plaice was related to sediment: no juvenile plaice were caught at locations with more than 10% mud fraction in the sediment. The distribution of 0‐group flounder was also correlated with sediment. Later in the year, salinity correlated negatively with the distribution of 0‐group flounder. The influence of sediment composition is probably indirect and linked to the abundance of preferred food items, such as Corophium volutator. Abiotic conditions were suitable to 0‐group plaice, flounder and sole.

ProblemDunes, beaches and surf zones have always protected the land against flooding by the sea. However, a sandy coast is more than just a pile of sand providing a natural defence against the sea. The protection of the Dutch coastal environment is laid down in (inter)national legislation and regulations, such as the EU Water Framework Directive (WFD), the EU Bird and Habitat Directive, and in international treaties and recommendations. Moreover, in 2006, the European Commission adopted the Marine Strategy Directive to protect the marine environment; it states that management of coasts should be based on an ecosystem approach (http://ec.europa.eu). To protect the coastal environment, one has to know what to protect and (i) what are its characteristics (ii) which organisms inhabit it and (iii) which functions does it fulfil? The surf zone of beaches is, however, rarely accessible for faunal sampling because of harsh and dynamic wave climate.On the Dutch coast, we assume that the main shortterm threats are sand nourishment to counter erosion, the mechanical cleaning of beaches, and disturbance by vehicles and tourists -all consequences of increasing recreational pressures, pollution and fisheries. Important Abstract Surf zones are highly dynamic, physically stressful parts of sandy beach ecosystems. The high wave energy of surf zones has in the past severely hampered ecological surveys of these systems. Here we used a novel technique to collect fauna from this environment along the Dutch coast. A large vehicle in the form a tripod that drives along the sandy seafloor and supports a sampling platform 11 m above the water line can collect both infaunal (grabs) samples and pull beam trawls for epibenthos. The distribution and diversity of macrofauna were studied at different depths in the surf zone along the Dutch coast. Species diversity and abundance increased with increasing depth of the water column. This increase was especially noticeable on the seaward side of the outer breaker bar. Within the surf zone, in the trough between the two breaker bars, there were spots of high diversity and abundance of macrobenthic infauna. Moreover, the area is also important for epibenthic and fish species, like the commercially important flatfish sole. Spatial patterns of species richness and abundance across an onshore-offshore gradient from the beach to seawards of the breakers suggest the presence of faunal zonation in this environment. The high abundance recorded in troughs was primarily caused by patches of juvenile Sand mason Lanice conchilega. The management implications of these results are that we suggest to protect the surf zone, including the trough between the two breaker bars, as a potential area of high diversity and abundance and to reconsider the objectives of the EU-Habitat Directive and the Water Framework Directive for the coastal area.

Field data on the pelagic occurrence of Corophium volutator were obtained in 1981–82 in the Dollard (Ems estuary). The pelagic population density averaged over a tidal half cycle was in the range 0–15 m-3. The pelagic population represents about 0.06% of the benthic population. On most sampling days pelagic occurrence resulted in a net flood surplus transport.