Field survey on juvenile bivalve densities October 2007Measurements made of density of chlorophyll, the velocity of the current and temperature.vessel: RV POSEIDON (IFM Geomar, Germany)sampling stations: 20 stations in OWEZ and 10 stations in each of the 5 reference areas R2, R3, R4, R5, RL (for geographic positions of stations see worksheet geographical positions stations)sampling design: 1 boxcore per stationsampling gear: NIOZ boxcorer, sampling depth 20 cm, sampling diameter 30 cmsample surface juvenile bivalves: 0.024 m2 (i.e. 3 sub-cores each with diameter 10 cm2 per boxcore)sample depth juvenile bivalves: 5 cmsorting procedure lab: stacked sieves 1.0, 0.5 and 0.2 mmfollowing worksheets describe: *number of identified juvenile bivalve species (> 0.5 mm) found per boxcore (0.024m2) and per m2Station,Date time,species,n bivalves > 0.5 mm per 0.024m2,n bivalves > 0.5 mm per m2

Observation of species living on the bottem of the North Sea.Field survey on macrobenthos communities February 2011vessel: RV PELAGIA (NIOZ, TEXEL)sampling stations: 16 stations in OWEZ and 8 stations in each of the 6 reference areas R1, R2, R3, R4, R5, R6sampling design: 1 boxcore per stationsampling gear: NIOZ boxcorer, sampling depth 20 cm, sampling diameter 30 cmsorting procedure lab:nested sieves 11.2 mm, 6.7 mm, 2 mm, and 1 mm; identification species:macrofauna identified to species level under a stereomicroscope;polychaetes, crustaceans, molluscs and echinoderms identified to species level;juveniles and damaged animals, if unidentifiable, identified at higher taxonomic level (usually the genus); anthozoans, phoronids, oligocheates, nemerteans and turbellaria identified on their taxon level;further procedures:all individuals counted; Individual lengths (mm) of molluscs and echinoids measured;blotted wet weights of polychaetes, larger crustaceans, and ophiuroids measured to the nearest mg; remaining taxa determined per species/group. Small crustaceans (amphipods and cumaceans) only counted.

The main purpose of this sampling was to study the effects of the OWEZ windpark on the demersal fish community. Because before installation of the windfarm the main fisheries activity in the area was bottom trawling, it is expected that exclusion of fisheries in the wind farm has the largest effect on the demersal fish community. The wind farm and its safety zone could function as a refugium for these species. If the area functions as a refugium this could be the case for a large number of demersal fish species that occur in the Dutch coastal zone. Owing to this a positive effect of the wind farm on the demersal fish community was expected. The fisheries that occurred in the area targeted larger fish, therefore fisheries mortality was higher on the larger fish. By excluding fisheries in the farm it was expected to change the size distribution in the farm and by that the age distribution of the fish populations. A Hydrolab minisonde, attached to the net, was used for continuous CTD measurements.