Benthic marine landscapes (BALANCE)

Summary This marine benthic landscape map of the Baltic Sea includes 60 broad scale habitat types which are defined according to different combinations of bottom substrate, photic zone and salinty level. Description This dataset was produced by the EU funded Balance project and maps the ecologically relevant benthic landscapes (broad-scale benthic habitats) of the Baltic Sea, identified on salinity, sediments and photic depth (as light touching the seabed). This marine benthic landscape map of the Baltic Sea includes 60 broad scale habitat types which are defined according to different combinations of bottom substrate, photic zone and salinty level. Each habitat is described with a three digit grid code, where the first digit refers to bottom substrate, the second digit refers to photic zone and the third refers to salinity. Description of grid code digits: Bottom substrate: 1= bedrock, 2 = hard bottom, 3 = sand, 4 = hard clay, 5 = mud Photic zone: 1 = photic, 2 = aphotic Salinity: 1 = 0-5 psu, 2 = 5 - 7.5 psu, 3 = 7.5 -11 psu, 4 = 11 - 18 psu, 5 = 18-30 psu, 6 = <30 psu The approach to marine landscape mapping within the Baltic Sea is based on the use of available physical, chemical and hydrographic data to prepare ecologically meaningful maps for areas with little or no biological information. It is basically a broad-scale map-ping/modelling approach based on presenting geophysical and hydrographical data in thematic GIS layers from which “marine landscapes” can be derived. In order to limit the number of possible landscapes the thematic layers are typically presented in a lim-ited number of categories reflecting shifts in major ecological entities (e.g. distinguish between habitats assumed to be within or below the photic zone). The approach aims to recognise the ecological linkage between major assemblages of species and the physical environment in which they reside. It can be applied to charac-terising broad-scale benthic complexity using parameters such as surface sediment, temperature, water motion, photic depth and slope and for semi-enclosed areas, like the Baltic Sea, salinity and oxygen content.Due to the limited resolution of the dataset, it should be only used for broadscale purposes. The dataset also requires verifications. (The quality of data collated differs from high to low-resolution data. Some of the modelled datasets has 7km resolution while others have ~600m resolution. All datasets were re-gridded to a 200 × 200m grid. This process ensures data continuity but it does not increase the out-put map resolution.)