We have estimated the standing stock biomass in carbon units per m² in the Baltic Sea ecosystem for 18 living and non-living groups relevant to carbon cycle and management activities in the Baltic Sea. We included three non-living apartments: POC, DOC and sediment carbon. The living groups comprise: phytoplankton, protozooplankton, bacteria, zooplankton, benthos, plaice, flounder, herring, sprat, cod, ringed seals, seals, grey seals and harbour porpoises. The estimates are based on ICES raw data and literature data and represent spatial and temporal averages. Data, data sources, assumptions and calculations are described in detail to ensure reproducibility.

2020-04-02: Changes to dataThe text of the description has been modified in the following documents:• A1_results_general_assumptions_methods• A2_detailed_assumptions_methodsThe main difference in content is a change in the estimation of the sediment stock and the associated method and a small change in the uncertainty estimate for ringed seals. In addition, the wording of the methods for benthos and macrophytes has been changed without changing the method or the result as such. This has been done to improve the clarity of the text.The above points have been changed accordingly in the related documents:• Mammals_data_and_calculation• Sediment_data_and_calculation• Benthos_data_and_calculation• Macrophytes_data_and_calculationAn incorrect equation in the commented R-scripts was corrected. Since this error was present in all three documents, the error was eliminated in:• Zooplankton_commented_Rscript• Phytoplankton_commented_Rscript• Protozooplankton_commented_Rscript