The pressure layer represents biological pressure caused by introduction of non-indigenous species. The data is obtained from core indicator Trend in the arrival of new non-indigenous species (BSEP 129b: http://www.helcom.fi/Lists/Publications/BSEP129B.pdf). For the Baltic Sea Impact Index, the layer was normalized.

This dataset represents the underlying data on core indicator Abundance of waterbirds in the breeding season 2018. The data is resulting from a data call carried out by HELCOM for State of the Baltic Sea report. Attribute information: "YEAR" = Year of the observation "SPECIES" = Species accepted scientific name "ABUNDANCE" = Abundance count "Country" = Country of observation "SITECODE" = Unique site code

This dataset describes fishing intensity for Otter mobile bottom contacting gear in 2010 based on VMS/Log book data processed by ICES Working Group on Spatial Fisheries Data (WGSFD). ICES secretariat collected during 2017 relevant VMS and logbook data for 2009-2016 to produce, as a technical service to HELCOM, updated spatial data layers on fishing intensity/pressure. Improved data quality control checks were implemented. Submitted data across the HELCOM area have improved in quality compared to previous data 2009-2013 published in 2015. Standardized methods were used to produce the requested data layers. The code used to create the data products is available here: https://github.com/ices-eg/wg_WGSFD For further technical information on the advice request, see http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2017/Special_requests/helcom.2017.18.pdf HELCOM secretariat did the following processing to the shapefile provided by ICES: - Conversion to ETRS89LAEA coordinate system - Added feature and attribute "Reported" to display unreported areas. Dataset attribute information: c-square: Unique reference of the c-square polygon Year: Year of fishing activity mid_lat: latitude coordinate of the centroid of c-square inWGS84 decimal degrees mid_lon: longitude coordinate of the centroid of c-square inWGS84 decimal degrees SurfaceSAR: Surface area ratio (Swept area, < 2 cm penetration depth of the gear components) Subsurface: Subsurface area ratio (Swept area, subsurface =>2 cm penetration depth of the gear components) totweight: Total Weight (kg) totvalue: Total value (Euros) Kw Fishing Hours: (Kw*h) Fishing hours: (h) Reported: Yes=Reported data. No= No reported data (area that does not contain effort/intensity value due to lack of reported data). Please note that this dataset was updated (v2) in January 2019, see further details below in the lineage section.

This dataset was collected by HELCOM Secretariat during the HELCOM MORE project and represents monitoring stations in the Baltic Sea. This dataset contains all nutrient stations in the Baltic Sea as reported to the HELCOM MORE project.

This dataset contains national information on dredging events where the material is not disposed at sea, reported by HELCOM Contracting Parties, as encouraged by HELCOM Recommendation 36/2 (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). Please note that this data collection is not conducted in all HELCOM countries, as this is not required under their national legislation, or the data might be unavailable for other reasons. The reporting of dredging sites is mandatory only for those events, where the dredged material is disposed at sea. This data set represents complimentary data of dredging sites where the material is NOT disposed at sea and where the reporting is done on voluntary basis, but still encouraged by the HELCOM Recommendation 36/2. The data regarding dredging activities where the material is not disposed at sea is usually not followed up upon. Therefore, the dataset may not include all dredging activities where the material is not disposed at sea nor is it certain that those activities included have been carried out. Attribute information Dredging ID: Unique id for the event, provided by data provider Latitude coordinate (WGS84, decimal degrees) Longitude coordinate (WGS84, decimal degrees) Dredging Activity: Type of dredging (Capital / Maintenance / Environmental) Description of dredged material: sand, silt, mud, clay, gravel, stones, rock, mixed, other (please specify) Date (dd/mm/yyyy): The date of the dredging event as precise as possible: dd/mm/yyyy, mm/yyyy or yyyy Year: Year of the dredging event Duration: An estimate of the duration of the dredging event Amount of material dredged Unit for the amount (ton/m3) Area of dredging event (m2): An estimation of the area dredged, if available Depth (m): An estimation of the depth where dredging occured Dredging method: digging/dredging device (open, enclosed), suction device, flushing, other (please specify) Notes: Other notes of the activity

Summary This dataset was collected by HELCOM Secretariat during the HELCOM MORE project and represents monitoring stations in the Baltic Sea Description This dataset contains all shared nutrient stations in the Baltic Sea as reported to the HELCOM MORE project. It was collected and published at the beginning of 2013.The data came originally from the CORESET project. Contracting Parties were then asked to complete and check the info.

Introduction of radionuclides is based on HELCOM MORS discharge data (2016-2020) . Annual averages of CO60, CS137 and SR90 from the period 2016-2020 per nuclear power plant. Gradual buffer around outlet to 10km distance (Type B decline). 10 km buffer with linear decline composed of 5 rings from discharges of radioactive substances (Type B decline)12.

Pressure layer combines all human activities that cause changes to hydrological conditions. The human activities were presented as point data which were given spatial extents (given below). The pressure value was given as the proportion of the grid cell under the pressure. Water course modification: 1 km buffer[10]. Location of water course modifications used for buffer. Overlaps removed and areas of buffer calculated per each grid cell. The final value was the area of the buffer in each individual cell. Wind farms: 300 m buffer around each turbine classified as operational, with linear decline (Type B decline), composed of 3 rings. Location of operational turbines as points were buffered and values given over linear decline. Oil platforms: 500 m buffer around each turbine with linear decline (Type B decline) composed of 5 rings. Location of oil platforms as points were buffered and values given over linear decline. Hydropower dams: A grid cell in the estuary. Locations of hydropower dams were crossed with rivers and the grid cell located in the end of the river was selected as presence (1) – those that are operational and produces energy. Other values in the grid were considered absence. [10] Extent based on wind farms and cables but expanded to 1 km because hydrological parameters are widely spreading. The human activity datasets were first processed separately covering the whole Baltic Sea and then summed together and overlapping areas were dissolved to remove double counting. Attenuation gradients are assigned to each layer as described above. Area effected decreases when distance from avtivity increases. Layer was normalized.

The pressure oil slicks and spills is combination of following datasets: • Illegal oil discharges • Polluting ship accidents Illegal oil discharge data is based on airborne surveillance with remote sensing equipment in the Baltic Sea Area. The area of the detected spills in 2011–2016 was used to represent the pressure. The value of spills under 1km2 were directly given to grid cell, spills over 1km2 were buffered based on estimate spill area. For polluting ship accidents the reported oil spill volumes (m3) in years 2011-2015 were used for the pressure. Some polluting ship accidents spills were missing spilled oil volume, thus a mean of reported volumes was given to accidents with missing oil volume. Datasets were handled separately. Both layers were normalized, summed and normalized again to produce the “oil slicks and spills” pressure layer. Please see below for further details.

Illegal oil discharges data is based on airborne surveillance supplemented with remote sensing equipment in the Baltic Sea Area carried out by HELCOM Contracting Parties within HELCOM IWGAS group. Aerial surveillance is limited within Russia and Latvia. Attribute information: "HELCOM_ID" = HELCOM ID "Country" = Country of observation "Year" = Year of observation "FlightType" = Flight observation performed at Day or Night "Date" = Date of the observation "Time_UTC" = Time of the observation (time zone is UTC) "Wind_speed" = Wind speed during observation "Wind_direc" = Wind direction during observation "Latitude" = longitude coordinate of observed oil spill "Longitude" = longitude coordinate of observed oil spill "Length__km" = length in km "Width__km_" = Width in km "Area__km2_" = Area in km2 "Spill_cat" = Spill category (oil or orther substance detected) "EstimVol_m" = Estimated volume of oil spill (m3) "Category" = Category of oil spill "SPILL" = Spill ID