The Habitats Directive is one of the main legal tools of the European Union to preserve biodiversity by maintaining and restoring natural habitats, and establishing a network of protected sites (NATURA 2000). One point of interest is the characterisation of marine habitats to localise the areas that fulfil the protection targets. Of the habitats listed in Annex I of the Habitats Directive, mainly
are relevant in the case of German Baltic offshore waters. Along a strong salinity gradient (5 to 25 psu), four planned offshore Marine Protected Areas (MPAs) within the German Exclusive Economic Zone (EEZ) of the Baltic Sea were thoroughly investigated in this study. More than 250 locations were analysed using a combination of standard sampling methods, underwater video technique, and measurement of abiotic factors (salinity, oxygen, sediment parameters). The areas of interest were the
Odra Bank (Oderbank), Adler Ground (Adlergrund), Kadet Trench (Kadetrinne)
Fehmarn Belt (Fehmarnbelt)
. The characteristic living communities (macrophytes, such as algae and sea grass, and macrozoobenthos such as worms, bivalves and crustaceans) for the different habitat types in these areas were characterised. Due to different salinity regimes, the benthic colonisation is different as well. In the Baltic Sea, with its decreasing salinity from west to east, the number of marine species declines, too. In the present study, altogether approximately 350 macrozoobenthic species and approximately 20 macrophytes were identified.