Final Report of the ICES/HELCOM Working Group on Integrated Assessments of the Baltic Sea (WGIAB)

The ICES/HELCOM Working Group on Integrated Assessments of the Baltic Sea (WGIAB) meeting was held at the Estonian University of Life Sciences in Tartu (Esto-nia) on 16–20 April 2018. The meeting was arranged to partly overlap with the annual meeting of the BONUS project “BLUEWEBS” organized at the same venue. Thanks to shared research interests and overlap in participants, we hope this could lead to some interesting and fruitful synergies and collaborations in future. The meeting was chaired by Saskia Otto (Germany), Martin Lindegren (Denmark), Lauréne Pécuchet (Finland), and Matilda Valman (Sweden).This was the third and final year of the three-year Terms of Reference (ToR) for WGIAB. The main working activities in 2018 were to i) investigate and compare long-term trends in community weighted mean (CWM) traits across subsystems; (ii) discuss and prepare an Ecosystem Overview document for the Baltic Sea; (iii) plan an overall synthesis paper of past and recent ecosystem trends and dynamics across Baltic Sea subsystems, (iv) revisit the Integrated Ecosystem Assessment (IEA) cycle and discuss ways to better align our work within this conceptual framework in future. In terms of the first activity, we have completed preliminary trait-based assessments of CMW traits in the Kattegat, Central Baltic Sea, and Gulf of Riga. These assessments demon-strate long-term changes in CWM traits across areas and multiple organism groups (including phytoplankton, zooplankton, benthos, and fish), largely related to changes in temperature, salinity, oxygen, and nutrients. Regarding the second activity, we have provided a qualitative (expert judgement based) ranking of key stressors and their im-pacts on ecosystem states, as well as distributed writing tasks among members to draft the ecosystem overview document. In terms of the third activity, we made a work plan outlining what areas, variables and methods to use for the synthesis paper, as well as assigned coordinators for each subsystem and an overall project leader. Due to time constraints, work on this activity will be carried out intersessionally. Under the fourth activity, we discussed the various steps in the IEA cycle, primarily focusing on the first and crucial “scoping” process that aims to identify key ecosystem objectives. Consen-sus was reached to focus on already available policies (e.g. the Marine Strategy Di-rective and the Baltic Sea Action Plan) from which key objectives and indicators have been defined and can be used in future efforts to close the IEA loop and make it oper-ational for management.In summary, the studies on changes in the Baltic Sea ecosystems and functional traits composition in relation to external drivers is expected to feed into the development of methods to assess the environmental status of Baltic Sea subsystems, and to ecosystem-based advice for fisheries management. The work to develop integrated assessments of social-ecological systems is anticipated to feed into integrated management towards the objectives of the common fisheries policy and the MSFD.