Use constraints: Data can be used freely given that the source is cited (following creative commons license CC-BY). The source should be cited as: “HELCOM HOLAS 3 Dataset (2023).

Data source: EUSeaMap 2021

Data processing: Original vector-based data on habitats (MSFD BHT) was first transformed 100x100m raster. The final value for the 1x1km grid was assigned to the habitat that had the biggest area within each grid cell. As contrary to HOLAS2, no aggregation to the habitats was made and the division of deep and shallow circalittoral habitats was kept. Thus the number of habitats used in HOLAS3 increased to 18.

Data quality: Broad habitat types describe the habitat distribution on a regional/large scale. They do not describe local scale variation in habitat distribution. Scale in the original data varies from 1:1 500 to 1:1 000 000.

All data is coming from one source, but given the uncertainties in the original data and data gaps in the southern Baltic Sea, the overall confidence can be considered to be moderate.

A separate confidence map of the original data, compiled by the EMODnet Seabed Habitats project, can be downloaded from the EMODnet Seabed Habitats thematic portal ( https://emodnet.ec.europa.eu/en/euseamap-2021-emodnet-broad-scale-seabed-habitat-map-europe) and viewed in the EUSeaMap 2021 technical report ( https://archimer.ifremer.fr/doc/00723/83528/88577.pdf).