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A common intention in ecosystem approach to management of marine resources worldwide has become a 'restoration of ecosystems' to some better shape. Although appealing, this political, rather vague aim has to be made more precise in order to be useful as a management objective. Therefore, a crucial role in defining EO, EQS, ES, ET, and similar characteristics set forward by, e.g. BSAP, MSFD, ND, UWWTD, and WFD as well as by many other acronyms to come, belongs to some conventional numbers that are considered as representing so-called background or reference conditions, which existed before significant man-made disturbances. At the Baltic Sea, experiencing human influence for centuries, quantification of the reference conditions and designing of desired state of restored marine ecosystems is complicated by both the uncertainty of which past times might be considered as reference times and the lack of essential observations from those times. One of the major, if not the only reliable method for reconstruction of the reference trophic state is it's simulation with biogeochemical models forced by the appropriate boundary conditions, including external nutrient inputs corresponding to the reference time interval. Once reconstructed, estimates of such "pristine" or, better to say, "pre-industrial" loads and their historical development can also be used both to test models' capabilities in reproducing pre-eutrophied state of the Baltic Sea and to study the very development of its eutrophication. Plausible solution of these problems gives more credibility to simulated responses of the marine ecosystems to scenarios of load reductions. For the Baltic Sea, such approach was initiated by Schernewski and Neumann (2005) and Savchuk et al. (2008) and further developed in the ECOSUPPORT Project (Gustafsson et al., 2012), where also a reconstruction of nutrient inputs since 1850 was briefly described. In order to facilitate distribution of reconstructed inputs and their usage, here we describe the process of reconstruction in more detail and make available the full data sets in digital form. The reconstructed external nutrient inputs comprise two periods. Land loads and atmospheric deposition in 1970-2006 are based on the best available data with sufficiently high coverage and resolution (Savchuk et al., 2012), while temporal dynamics over 1850-1970 were interpolated between estimates prescribed for a few fixed years. Similarly to the dataset for 1970-2006, the reconstructed inputs are aggregated according to the spatial segmentation of the Baltic Sea (Fig. 1) currently implemented in the biogeochemical model BALTSEM (BAltic sea Long-Term large Scale Eutrophication Model).

Legislations and commitments regulate Baltic Sea status assessments and monitoring. These assessments suffer from monitoring gaps that need prioritization. We used three sources of information; scientific articles, project reports and a stakeholder survey to identify gaps in relation to requirements set by the HELCOM's Baltic Sea Action Plan, the Marine Strategy Framework Directive and the Water Framework Directive. The most frequently mentioned gap was that key requirements are not sufficiently monitored in space and time. Biodiversity monitoring was the category containing most gaps. However, whereas more than half of the gaps in reports related to biodiversity, scientific articles pointed out many gaps in the monitoring of pollution and water quality. An important finding was that the three sources differed notably with respect to which gaps were mentioned most often. Thus, conclusions about gap prioritization for management should be drawn after carefully considering the different viewpoints of scientists and stakeholders. ; publishedVersion