Use constraints: Free for non-commercial purposes. Reference must be made to data source (BALANCE).

This dataset shows model results forthe distribution of where at least 1% available light touches the seabed (the photic zone) and non-photic zone in the Baltic Sea based on 1% mean annual irradiance. (Data source: DHI Water - Environment - Health and ICES, produced by BSR INTERREG IIIB project BALANCE)

For the purpose of mapping the photic zone in the Kattegat and Baltic Sea water transparency has been calculated utilizing Secchi disc depth. The data have been collected at the ICES homepage, http://www.ices.dk/Ocean/project/secchi/ (Aarup 2002). The data

covers measurements of Secchi disc depth (SD) from the period 1903 to 1998. However, for this study only data from 1980-1998 was used. Also, only data between March to October have been included to account for the productive period providing approximately 20.000 records. In situations where frequent data are available at the same station, the data have been averaged per station resulting in approximately 2800 records covering most of the Baltic Sea area and Kattegat. These 2800 records have been spatially interpolated and extrapolated to cover the Baltic Sea. With this approach the station locations is weighted equally with the number of measurements. Despite the rich amount of data, the measurements of SD are not evenly distributed and areas in the Baltic Proper, Gulf of Riga and southern Baltic are not well covered.

For more information about this dataset see BALANCE Interim Report no. 10 "Towards marine landscapes in the Baltic Sea": http://balance-eu.org/xpdf/balance-interim-report-no-10.pdf.