The eutrophication status of the Oslofjord, Norway, was assessed using 1) existing monitoring data, 2) established assessment criteria, and 3) an updated version of the HELCOM Eutrophication Assessment Tool (HEAT), which is widely employed in Europe. The analysis, covering the period from 1960 to 2023, revealed persistent 'eutrophication problem areas' in specific regions of the Oslofjord, particularly in inner areas and those situated downstream of large catchments and urban centres. This assessment demonstrated that the Oslofjord has been classified as a 'eutrophication problem area' for more than five decades. These findings, including basin- and criteria-specific distance-to-target estimates, provide a foundation for establishing evidence-based nutrient management strategies in the Oslofjord and its upstream catchments. In the absence of reduced nutrient inputs, a significant portion of the Oslofjord will continue to be classified as a 'problem area'.

Expert knowledge can help fill gaps in quantitative empirical information about complex ecological phenomena. We examined the level of agreement between 21 studies that collected expert ratings of the sensitivity of species and habitats to human activities and their pressures as input data for mapping the human impact on marine ecosystems. Our analyses revealed broad agreement about which human activities and pressures many species and habitats are sensitive to. These agreements reflect a common view of the main threats to ocean ecosystems. In contrast, scores provided by individual experts varied both within and across studies. Sensitivity scores collected with the same method for different regions were often more similar than scores collected for the same region but with different methods. These results highlight how inconsistencies in the design of many expert surveys can lead to variable outcomes. It is important to employ more consistent and theoretically grounded methods and protocols when eliciting expert ratings of species’ sensitivity to pressures, to ensure compatibility across studies and maintain rigour in analyses supporting effective ocean management.

Human activities at sea can produce pressures and cumulative effects on ecosystem components that need to be monitored and assessed in a cost-effective manner. Five Horizon European projects have joined forces to collaboratively increase our knowledge and skills to monitor and assess the ocean in an innovative way, assisting managers and policy-makers in taking decisions to maintain sustainable activities at sea. Here, we present and discuss the status of some methods revised during a summer school, aiming at better management of coasts and seas. We include novel methods to monitor the coastal and ocean waters (e.g. environmental DNA, drones, imaging and artificial intelligence, climate modelling and spatial planning) and innovative tools to assess the status (e.g. cumulative impacts assessment, multiple pressures, Nested Environmental status Assessment Tool (NEAT), ecosystem services assessment or a new unifying approach). As a concluding remark, some of the most important challenges ahead are assessing the pros and cons of novel methods, comparing them with benchmark technologies and integrating these into long-standing time series for data continuity. This requires transition periods and careful planning, which can be covered through an intense collaboration of current and future European projects on marine biodiversity and ecosystem health.

Environmental policies such as the Water Framework Directive (WFD) requires that the confidence of ecological status assessments should be reported. Such assessments are typically based on aggregating several ecological indicators, but the uncertainty of these is rarely quantified and when exceptionally it is estimated, the indicator variance can be grossly underestimated, resulting in overconfident assessment. We demonstrate with a simple example that incorrect partitioning of different sources of variation, typically characterizing monitoring data, can underestimate the standard error of an indicator by 33 %. This is due to sampling constraints in monitoring programs, implying that observations are not independent replicates across all levels of sampling. We also carried out a comprehensive analysis, quantifying the magnitude of different sources of variation for monitoring variables used to calculate ecological indicators for WFD status classification in Sweden. We demonstrate that these variances can be estimated from regular monitoring data, although it was not possible to estimate all relevant sources of variation. We propose to occasionally include spatial and temporal replicate samples in the existing monitoring programs such that relevant sources of uncertainty can be quantified with sufficient precision. This library of variance parameter estimates allows for calculating the uncertainty of ecological indicators more correctly for any combination of sampling in time and space by different institutions/taxonomists. It also identifies the dominant sources of random variation affecting the indicator uncertainty, providing a basis for optimal sampling design as well as potential improvement of current sampling and analysis procedures, both aiming at reducing uncertainty. Whilst it is commonly understood that sampling occasions should be spread appropriately across time and space, the relatively large variability among institutes/taxonomists implies that spreading samples among these also helps reducing indicator uncertainty, particularly for biological indices. It is important to change the perception that ecological indicators can stand alone as single values, without considering the associated uncertainties which allow for quantifying the confidence in ecological status assessments. This study demonstrates that this is possible based on appropriate partitioning of sources of uncertainty.

We report the outcomes of a comprehensive study of the potential consequences of the implementation of the EU Maritime Spatial Planning Directive (MSPD) in Danish waters. The analyses are anchored in a framework developed in support of data-driven Ecosystem-Based Maritime Spatial Planning. The data for the models include not only human stressors but also information on the distribution of ecosystem components ranging from planktonic communities over benthic communities to fish, seabirds and marine mammals. We have established a baseline, based on state-of-the-art data sets, with respect to combined effects upon ecosystem components. Future scenarios for the developments in human stressors were estimated for 2030 and 2050 based on information on existing policies, strategies and plans and were compared to the baseline. In addition, we developed a scenario for implementation of the Marine Strategy Framework Directive (MSFD), i.e. working towards meeting the objectives of Good Environmental Status. Our results indicate that (1) combined human stressors will possibly increase in 2030 and 2050 compared to the baseline, (2) increased combined human stressors are likely to lead to a worsening of the environmental and ecological status sensu the Marine Strategy Framework Directive and the Water Framework Directive (WFD), and (3) the MSPD implementation process appears to conflict with the MSFD and WFD objectives. Accordingly, we are sceptical of claims of an untapped potential for Blue Growth in Danish marine waters.

We demonstrate a prototype multi-metric indicator-based assessment tool (i.e. Marine Litter Assessment Tool MALT) for mapping and identification of 'problem areas' and 'non-problem areas' regarding the occurrence of marine litter in Europe's seas. The study is based on a European-wide data set consisting of three marine litter indicators: (1) litter at the seafloor, (2) beach litter and (3) floating micro-litter. This publicly available data allowed litter status to be determined in 1,957,081 km2 (19.1 %) of the total area of Europe's seas (10,243,474 km2). Of the area assessed, 25.8 % (505,030 km2) was found to be 'non-problem areas' whilst 'problem areas' accounted for 74.2 % (1,452,051 km2). This indicates that marine litter is a large-scale problem in Europe's seas.

Ecosystem responses to increasing human pressures are complex and diverse, affecting organisms across all trophic levels. This has prompted the development of methods that integrate information across many indicators for environmental management. Legislative frameworks such as the European Water Framework Directive (WFD), specifically prescribe that integrated assessme nt (IA) of ecological status must consider indicators representing various biological and supporting quality elements. We present a general approach for an IA system based on a piece-wise linear transformation of indicator distributions to a standardized scale, allowing for integrating information from multiple and diverse indicators through a policy-dependent aggregation scheme. Uncertainties associated with monitoring data used for calculating indicators and their propagation throughout the integration scheme allow for confidence assessment at all levels of the hierarchical integration. Specific pressures leading to ecological impact can be identified through the most impaired indicators in the hierarchical and transparent aggregation scheme. The IA and its confidence are facilitated though the development of an online tool that accesses information from monitoring databases and presents the outcome at all levels of the assessment, ensuring consistency and transparency in the calculations for all potential stakeholders. We demonstrate the versality and applicability of the approach using indicators and aggregation principles from the Swedish national guidelines for assessing ecological status of rivers, lakes and coastal waters according to the WFD. Although the approach and the tool were developed specifically for the WFD ecological status assessment in Sweden, the generality of the approach implies that it can easily be adapted to the WFD assessment methods of other countries as well as other policies, where an integrated assessment is required.

We report identification and mapping of areas in Europe’s seas and coastal areas impacted by contaminants, i.e., areas with concentrations above internationally agreed threshold values. The study is based on (1) a state-of-the-art data set anchored in national monitoring activities, (2) internationally agreed target values and (3) an updated version of the CHASE assessment tool (originally: the HELCOM Chemical Status Assessment Tool). The spatial cover of data enabled us to classify 1,518 spatial assessment units, with 80% of the area assessed determined to be “problem areas”. We have demonstrated that it is possible to make an integrated assessment of contaminants spanning over four marine regions, and 10 marine sub-regions (sensu the EU Marine Strategy Framework Directive), including marine and coastal waters of 30 European countries. The power of combining data of different sources and contaminant categories over larger geographical scales, is potentially and in a long-term perspective the way forward for wider use of multi-metric indicator-based assessment tools supporting informed decision-making.

Marine ecosystems are under high demand for human use, giving concerns about how pressures from human activities may affect their structure, function, and status. In Europe, recent developments in mapping of marine habitats and human activities now enable a coherent spatial evaluation of potential combined effects of human activities. Results indicate that combined effects from multiple human pressures are spread to 96% of the European marine area, and more specifically that combined effects from physical disturbance are spread to 86% of the coastal area and 46% of the shelf area. We compare our approach with corresponding assessments at other spatial scales and validate our results with European-scale status assessments for coastal waters. Uncertainties and development points are identified. Still, the results suggest that Europe’s seas are widely disturbed, indicating potential discrepancy between ambitions for Blue Growth and the objective of achieving good environmental status within the Marine Strategy Framework Directive.

We modelled and assessed the past, present and predicted future eutrophication status of the Baltic Sea. The assessment covers a 350-year period from 1850 to 2200 and is based on: (1) modelled concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorous (DIP), chlorophyll-a, Secchi depth, and oxygen under four different of nutrient input scenarios and (2) the application of a multi-metric indicator-based tool for assessment of eutrophication status: HEAT 3.0. This tool was previously applied using historical observations to determine eutrophication status from 1901 to 2012. Here we apply HEAT 3.0 using results of a biogeochemical model to reveal significant changes in eutrophication status from 1850 to 2200. Under two scenarios where Baltic Sea Action Plan (BSAP) nutrient reduction targets are met, we expect future good status will be achieved in most Baltic Sea basins. Under two scenarios where nutrient loads remain at 1997-2003 levels or increase, good status will not be achieved. The change from a healthy state without eutrophication problems in the open waters took place in the late 1950s and early 1960s. Following introduction of the first nutrient abatement measures, recovery began in some basins in the late 1990s, whilst in others it commenced in the beginning of the 21st century. Based on model results, we expect that the first basin to achieve a status without eutrophication will be Arkona, between 2030 and 2040. By 2060-2070, a status without eutrophication is anticipated for the Kattegat, Bornholm Basin and Gulf of Finland, followed by the Danish straits around 2090. For the Baltic Proper and Bothnian Sea, a good status with regard to eutrophication will not be expected before 2200. Further, we conclude that two basins are not likely to meet the targets agreed upon and to attain a status unaffected by eutrophication, i.e. the Gulf of Riga and Bothnian Bay. These results, especially the prediction that some basins will not achieve a good status, can be used in support of continuous development and implementation of the regional ecosystem-based nutrient management strategy, the HELCOM Baltic Sea Action Plan.

The objectives of this study are 1) to map the potential cumulative impacts of multiple human activities and stressors on the ecosystems in the transition zone between the North Sea and Baltic Sea, for Danish waters 2) to analyse differences in stressor contribution between the European Union's Marine Strategy Framework Directive (MSFD, off-shore waters) and Water Framework Directive (WFD, coastal waters), and 3) to assess the local relative importance of stressors for 14 areas along a land-sea gradient, from inner fjords or coastal areas to offshore waters. The mapping of cumulative impacts is anchored in 35 datasets describing a broad range of human stressors and 47 ecosystem components ranging from phytoplankton over benthic communities to fish, seabirds and marine mammals, which we combined by means of a widely used spatial human impact model. Ranking of the stressor impacts for the entire study area revealed that the top five stressors are: 'Nutrients', 'Climate anomalies', 'Non-indigenous species', 'Noise' and 'Contaminants'. The gradient studies showed that some stressors (e.g. 'Nutrients', 'Shipping' and 'Physical modification') have a relatively higher impact within the fjord/estuarine systems whilst others (e.g. 'Fisheries', 'Contaminants' and 'Noise') have relatively higher impact in the open waters. Beyond mapping of cumulative human impacts, we discuss how the maps can be used as an analytical tool to inform ecosystem-based management and marine spatial planning, using the MSFD and WFD as examples.

BEAT 3.0 is a multi-metric indicator-based tool for integrated assessments of marine biodiversity status implemented in R. It follows the structure and requirements of the EU Marine Strategy Framework Directive and allows for use of monotonic, unimodal, conditional, trend-based and qualitative indicators. The tool handles tabular data files (.txt format), in which the assessment structure and indicator results are specified. Integration of indicators is primarily based on weighted averaging, where both spatial assessment scale and ecosystem level are considered. Parallel to the biodiversity status assessment, a confidence assessment is also included. BEAT 3.0 uses HELCOM Assessment units and HELCOM core indicators as default but can be customized for use in any geographical region and any set of indicators. Funding Statement: BEAT 3.0 was developed in the HELCOM coordinated EU co-financed project ‘Baltic Sea project to boost regional coherence of marine strategies through improved data flow, assessments, and knowledge base for development of measures (BalticBOOST)’ EU grant number 11.0661/2015/712632/SUB/ENVC.2.