Deoxygenation of the Baltic Sea during the last century.

Deoxygenation is a global problem in coastal and open regions of the ocean, and has led to expanding areas of oxygen minimum zones and coastal hypoxia. The recent expansion of hypoxia in coastal ecosystems has been primarily attributed to global warming and enhanced nutrient input from land and atmosphere. The largest anthropogenically induced hypoxic area in the world is the Baltic Sea, where the relative importance of physical forcing versus eutrophication is still debated. We have analyzed water column oxygen and salinity profiles to reconstruct oxygen and stratification conditions over the last 115 y and compare the influence of both climate and anthropogenic forcing on hypoxia. We report a 10-fold increase of hypoxia in the Baltic Sea and show that this is primarily linked to increased inputs of nutrients from land, although increased respiration from higher temperatures during the last two decades has contributed to worsening oxygen conditions. Although shifts in climate and physical circulation are important factors modulating the extent of hypoxia, further nutrient reductions in the Baltic Sea will be necessary to reduce the ecosystems impacts of deoxygenation.

Development and testing of a prototype tool for integrated assessment of chemical status in marine environments.

We report the development and application of a prototype tool for integrated assessment of chemical status in aquatic environments based on substance- and matrix-specific environmental assessment criteria (thresholds). The Chemical Status Assessment Tool (CHASE) integrates data on hazardous substances in water, sediments and biota as well as bio-effect indicators and is based on a substance- or bio-effect-specific calculation of a 'contamination ratio' being the ratio between an observed concentration and a threshold value. Values <1.0 indicate areas potentially 'unaffected', while values >1.0 indicate areas potentially 'affected'. These ratios are combined within matrices, i.e. for water, sediment and biota and for biological effects. The overall assessment used a 'one out, all out principle' with regard to each matrix. The CHASE tool was tested in the Baltic Sea and the North Sea in 376 assessment units. In the former, the chemical status was >1.0 in practically all areas indicating that all areas assessed were potentially affected. The North Sea included areas classified as unaffected or affected. The CHASE tool can in combination with temporal trend assessments of individual substances be advantageous for use in remedial action plans and, in particular, for the science-based evaluation of the status and for determining which specific substances are responsible for a status as potentially affected.

Nitrogen inputs from agriculture: towards better assessments of eutrophication status in marine waters.

Nutrient enrichment of coastal marine waters caused by losses of nitrate (NO(3)(-)) from agriculture is an increasing global problem. In the European Union, the Nitrates Directive (ND) of 1991 was meant to be a cornerstone in reducing eutrophication effects in coastal waters downstream from intensively farmed catchments. Although reductions in losses of nitrate have been attained, very few Member States have yet been able to reduce eutrophication effects caused by inputs of NO(3)(-) from agriculture. We report trends in concentrations of NO(3)(-) and chlorophyll-a (Chl-a) in Danish coastal and open marine waters during the period from 1996 to 2011 together with an assessment of eutrophication status based on multiple indicators (e.g. nutrient concentrations, Chl-a, submerged aquatic vegetation and benthic macroinvertebrates). Despite decreasing concentrations of both NO(3)(-)and Chl-a, Danish coastal waters are not yet to be classified as 'unaffected by eutrophication'. In order to improve future pan-European evaluations of the effectiveness of the ND, we argue for the added value of including indicators and assessment principles from other European Directives, i.e. the Water Framework Directive and the Marine Strategy Framework Directive.

Development and testing of a prototype indicator-based tool for identification of potential problem areas for marine litter in Europe's seas.

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.

Are European Blue Economy ambitions in conflict with European environmental visions?

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.

Monitoring of environmental DNA from nonindigenous species of algae, dinoflagellates and animals in the North East Atlantic.

Monitoring the distribution of marine nonindigenous species is a challenging task. To support this monitoring, we developed and validated the specificity of 12 primer-probe assays for detection of environmental DNA (eDNA) from marine species, all nonindigenous to Europe. The species include sturgeons, a Pacific red algae, oyster thief, a freshwater hydroid from the Black Sea, Chinese mitten crab, Pacific oyster, warty comb jelly, sand gaper, round goby, pink salmon, rainbow trout and North American mud crab. We tested all assays in the laboratory, on DNA extracted from both the target and non-target species to ensure that they only amplified DNA from the intended species. Subsequently, all assays were used to analyse water samples collected at 16 different harbours across two different seasons during 2017. We also included six previously published assays targeting eDNA from goldfish, European carp, two species of dinoflagellates of the genera Karenia and Prorocentrum, two species of the heterokont flagellate genus Pseudochattonella. Conventional monitoring was carried out alongside eDNA sampling but with only one sampling event over the one year. Because eDNA was relatively fast and easy to collect compared to conventional sampling, we sampled eDNA twice during 2017, which showed seasonal changes in the distribution of nonindigenous species. Comparing eDNA levels with salinity gradients did not show any correlation. A significant correlation was observed between number of species detected with conventional monitoring methods and number of species found using eDNA at each location. This supports the use of eDNA for surveillance of the distribution of marine nonindigenous species, where the speed and relative easy sampling in the field combined with fast molecular analysis may provide advantages compared to conventional monitoring methods. Prior validation of assays increases taxonomic precision, and laboratorial setup facilitates analysis of multiple samples simultaneously. The specific eDNA assays presented here can be implemented directly in monitoring programmes across Europe and potentially worldwide to infer a more precise picture of the dynamics in the distribution of marine nonindigenous species.

Combined effects of human pressures on Europe's marine ecosystems.

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.

Relative impacts of multiple human stressors in estuaries and coastal waters in the North Sea-Baltic Sea transition zone.

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.

Cumulative impact assessment for ecosystem-based marine spatial planning.

Claims for ocean space are growing while marine ecosystems suffer from centuries of insufficient care. Human pressures from runoff, atmospheric emissions, marine pollution, fishing, shipping, military operations and other activities wear on habitats and populations. Ecosystem-based marine spatial planning (MSP) has emerged worldwide as a strategic instrument for handling conflicting spatial claims among competing sectors and the environment. The twofold objective of both boosting the blue economy and protecting the environment is challenging in practice and marine planners need decision support. Cumulative Impact Assessment (CIA) was originally developed to provide an overview of the human imprint on the world's ocean ecosystems. We have now added a scenario component to the CIA model and used it within Swedish ecosystem-based MSP. This has allowed us to project environmental impacts for different planning alternatives throughout the planning process, strengthening the integration of environmental considerations into strategic decision-making. Every MSP decision may entail a local shift of environmental impact, causing positive or negative consequences for ecosystem components. The results from Swedish MSP in the North Sea and Baltic Sea illustrate that MSP certainly has the potential to lower net cumulative environmental impact, both locally and across sea basins, as long as environmental values are rated high and prevailing pressures derive from activities that are part of MSP. By synthesizing innumerous data into comprehensible decision support that informs marine planners of the likely environmental consequences of different options, CIA enables ecosystem-based MSP in practice.

Long-term temporal and spatial trends in eutrophication status of the Baltic Sea.

Much of the Baltic Sea is currently classified as 'affected by eutrophication'. The causes for this are twofold. First, current levels of nutrient inputs (nitrogen and phosphorus) from human activities exceed the natural processing capacity with an accumulation of nutrients in the Baltic Sea over the last 50-100 years. Secondly, the Baltic Sea is naturally susceptible to nutrient enrichment due to a combination of long retention times and stratification restricting ventilation of deep waters. Here, based on a unique data set collated from research activities and long-term monitoring programs, we report on the temporal and spatial trends of eutrophication status for the open Baltic Sea over a 112-year period using the HELCOM Eutrophication Assessment Tool (HEAT 3.0). Further, we analyse variation in the confidence of the eutrophication status assessment based on a systematic quantitative approach using coefficients of variation in the observations. The classifications in our assessment indicate that the first signs of eutrophication emerged in the mid-1950s and the central parts of the Baltic Sea changed from being unaffected by eutrophication to being affected. We document improvements in eutrophication status that are direct consequences of long-term efforts to reduce the inputs of nutrients. The reductions in both nitrogen and phosphorus loads have led to large-scale alleviation of eutrophication and to a healthier Baltic Sea. Reduced confidence in our assessment is seen more recently due to reductions in the scope of monitoring programs. Our study sets a baseline for implementation of the ecosystem-based management strategies and policies currently in place including the EU Marine Strategy Framework Directives and the HELCOM Baltic Sea Action Plan.

Approaches for integrated assessment of ecological and eutrophication status of surface waters in Nordic Countries.

We review approaches and tools currently used in Nordic countries (Denmark, Finland, Norway and Sweden) for integrated assessment of 'ecological status' sensu the EU Water Framework Directive as well as assessment of 'eutrophication status' in coastal and marine waters. Integration principles for combining indicators within biological quality elements (BQEs) and combining BQEs into a final-integrated assessment are discussed. Specific focus has been put on combining different types of information into indices, since several methods are currently employed. As a consequence of the variety of methods used, comparisons across both BQEs and water categories (river, lakes and coastal waters) can be difficult. Based on our analyses, we conclude that some principles and methods for integration can be critical and that a harmonised approach should be developed. Further, we conclude that the integration principles applied within BQEs are critical and in need of harmonisation if we want a better understanding of potential transition in ecological status between surface water types, e.g. when riverine water enters a downstream lake or coastal water body.

Force majeure: Will climate change affect our ability to attain Good Environmental Status for marine biodiversity?

The EU Marine Strategy Framework Directive (MSFD) requires that Good Environmental Status (GEnS), is achieved for European seas by 2020. These may deviate from GEnS, its 11 Descriptors, targets and baselines, due to endogenic managed pressures (from activities within an area) and externally due to exogenic unmanaged pressures (e.g. climate change). Conceptual models detail the likely or perceived changes expected on marine biodiversity and GEnS Descriptors in the light of climate change. We emphasise that marine management has to accommodate 'shifting baselines' caused by climate change particularly during GEnS monitoring, assessment and management and 'unbounded boundaries' given the migration and dispersal of highly-mobile species. We suggest climate change may prevent GEnS being met, but Member States may rebut legal challenges by claiming that this is outside its control, force majeure or due to 'natural causes' (Article 14 of the MSFD). The analysis is relevant to management of other global seas.

Palaeoecology, reference conditions and classification of ecological status: the EU Water Framework Directive in practice.

The European Union's Water Framework Directive (WFD) requires that all Member States within the European Union determine reference conditions for aquatic ecosystems to provide a baseline against which to measure the effects of past and present activities. Reference conditions are subsequently used to classify the ecological status of European waters. The decisions regarding environmental status will be important future elements in the management of European coastal waters. We have developed a number of classification scenarios for total nitrogen (TN) in the overlying waters of the southern part of Roskilde Fjord, Denmark, taking as our basis a palaeoecological reconstruction of fluctuations in TN between 1850 and 1995. We present a provisional classification scheme for the ecological status of Roskilde Fjord, sensu the WFD. Decision(s) regarding the deviation from reference conditions will give a wide range of apparent ecological status from good, through moderate and poor, to bad depending upon the definition of an acceptable deviation from reference conditions. The determination of an acceptable deviation will ultimately be a political decision, and will result in a wide range in the protection of coastal waters in Europe. There is still, however, an urgent need for a sound scientific documentation of the various scenarios for the implementation of the WFD.

Good Environmental Status of marine ecosystems: what is it and how do we know when we have attained it?

The European Marine Strategy Framework Directive (MSFD) requires EU Member States (MS) to achieve Good Environmental Status (GEnS) of their seas by 2020. We address the question of what GEnS entails especially with regard to the level at which targets are set (descriptors, criteria, indicators), to scales for assessments (regional, sub-divisions, site-specific), and to difficulties in putting into practice the GEnS concept. We propose a refined and operational definition of GEnS, indicating the data and information needed to all parts of that definition. We indicate the options for determining when GEnS has been met, acknowledge the data and information needs for each option, and recommend a combination of existing quantitative targets and expert judgement. We think that the MSFD implementation needs to be less complex than shown for other similar directives, can be based largely on existing data and can be centred on the activities of the Regional Seas Conventions.

A simple method for confidence rating of eutrophication status classifications.

We report the development of a methodology for assessing confidence in ecological status classifications. The method presented here can be considered as a secondary assessment, supporting the primary assessment of eutrophication or ecological status. The confidence assessment is based on scoring the quality of the indicators on which the primary assessment is made. This represents a first step towards linking status classification with information regarding their accuracy and precision. Applied to an existing data set used for assessment of eutrophication status of the Baltic Sea (including the Kattegat and Danish Straits) we demonstrate that confidence in the assessment is Good or High in 149 out of 189 areas assessed (79%). Contrary to our expectations, assessments of the open parts of the Baltic Sea have a higher confidence than assessments of coastal waters. We also find that in open waters of the Baltic Sea, some biological indicators have a higher confidence than indicators representing physical-chemical conditions. In coastal waters, phytoplankton, submerged aquatic vegetation and indicators of physical-chemical conditions have a higher confidence than indicators of the quality of benthic invertebrate communities. Our analyses also show that the perceived weaknesses of eutrophication assessments are due more to Low confidence in reference conditions and acceptable deviations, rather than in the monitoring data.

Phylogeny of green sulfur bacteria on the basis of gene sequences of 16S rRNA and of the Fenna-Matthews-Olson protein.

The phylogeny of green sulfur bacteria was studied on the basis of gene sequences of the 16S rRNA and of the Fenna-Matthews-Olson (FMO) protein. Representative and type strains (31 strains total) of most of the known species were analyzed. On the basis of fmoA gene sequences from Chlorobium tepidum ATCC 49652(T) and Chlorobium limicola DSM 249(T) available from the EMBL database, primers were constructed that allowed sequence analysis of a major part of the fmoAgene. The largely congruent phylogenetic relationship of sequences of the fmoA gene and of 16S rDNA gives considerable support to the phylogeny of green sulfur bacteria previously suggested on the basis of 16S rDNA sequences. Distinct groups of strains were recognized on the basis of 16S rDNA and FMO sequences and supported by characteristic signature amino acids of FMO. Marine strains formed clusters separate from freshwater strains. The resulting phylogenetic grouping and relationship of the green sulfur bacteria do not correlate with their current taxonomic classification.