Use constraints: The data can be used freely for non-commercial purposes but EU-funded Balance project should always be cited as the data source.

As the first step the necessary environmental parameters and data sets were selected for the identification of marine landscapes in the Baltic Sea. The next step was to harmonise and standardise the selected individual data sets and present them in unified formats. To produce the broad-scale benthic marine landscape map from a number of different sources efficiently raster map algebra in a GIS was used.

The primary environmental parameters included for the developing the benthic marine landscapes were sediment, the photic – non-photic zone (where 1% of available light reaches the seabed) and salinity as they are important for determining broad-scale dis-tribution of species in a regional Baltic Sea context.

National seabed sediment classification categories were harmonized in order to produce one classification scheme, which had to be as simple as possible, but still take into account biological importance. The resulting classification scheme consisting of five sediment classes are applied in the mapping and modelling of the Baltic Sea marine landscapes. These are:

I. Bedrock.

II. Hard bottom complex, includes patchy hard surfaces and coarse sand (some-times also clay) to boulders.

III. Sand including fine to coarse sand (with gravel exposures).

IV. Hard clay sometimes/often/possibly exposed or covered with a thin layer of sand/gravel.

V. Mud including gyttja-clay to gyttja-silt.

Available light at the seabed was included and divided into two categories, the photic and non-photic zones.

The Baltic Sea is characterised by some fairly stable salinity gradients ranging from > 30psu in the northern Kattegat to almost fresh water in the Bothnian Bay. As the salt concentration influences marine life in a number of different ways, salinity was split into 6 categories reflecting the distribution of structuring species.

The approach used by the BALANCE project is fully applicable for an ecologically relevant characterisation of the Baltic Sea, however, end users might find it necessary to validate and further refine and improve the maps. Such validations and refinements are necessary in order to fully exploit the potential application of the maps and for linking them to the implementation of national and international legislation.

For more information, see the Balance technical summary report no. 2 Baltic Sea marine landscapes and habitats: Mapping and modelling ( http://balance-eu.org/xpdf/balance-technical-summary-report-no-2-4.pdf).