Baltic Sea hazardous substances management: results and challenges

The introduction into the Baltic Sea of hazardous substances that are persistent, bioaccumulate, and are toxic is an important environmental and human health problem. Multilateral efforts to address this problem have primarily been taken under the Helsinki Commission (HELCOM). This article examines past HELCOM efforts on hazardous substances, and discusses future challenges regarding their management. The article finds that past actions on hazardous substances have had a positive effect on improving Baltic environmental quality and reducing human health risks, although there are remaining issues and difficulties that need to be addressed. In particular, four related future challenges for HELCOM management of hazardous substances are identified and discussed: i) the need to engender further implementation and building public and private sector capacities; ii) the need to improve data availability, quality and comparability across the region and international fora; iii) the need to strengthen existing regulations and incorporate new issues; and iv) the need to effectively coordinate HELCOM activities with efforts on hazardous substances in other international fora.     

Projected future climate change and Baltic Sea ecosystem management

Climate change is likely to have large effects on the Baltic Sea ecosystem. Simulations indicate 2–4 °C warming and 50–80 % decrease in ice cover by 2100. Precipitation may increase ~30 % in the north, causing increased land runoff of allochthonous organic matter (AOM) and organic pollutants and decreased salinity. Coupled physical–biogeochemical models indicate that, in the south, bottom-water anoxia may spread, reducing cod recruitment and increasing sediment phosphorus release, thus promoting cyanobacterial blooms. In the north, heterotrophic bacteria will be favored by AOM, while phytoplankton production may be reduced. Extra trophic levels in the food web may increase energy losses and consequently reduce fish production. Future management of the Baltic Sea must consider the effects of climate change on the ecosystem dynamics and functions, as well as the effects of anthropogenic nutrient and pollutant load. Monitoring should have a holistic approach, encompassing both autotrophic (phytoplankton) and heterotrophic (e.g., bacterial) processes.     

Baltic Sea ecosystem-based management under climate change: Synthesis and future challenges

Ecosystem-based management (EBM) has emerged as the generally agreed strategy for managing ecosystems, with humans as integral parts of the managed system. Human activities have substantial effects on marine ecosystems, through overfishing, eutrophication, toxic pollution, habitat destruction, and climate change. It is important to advance the scientific knowledge of the cumulative, integrative, and interacting effects of these diverse activities, to support effective implementation of EBM. Based on contributions to this special issue of AMBIO, we synthesize the scientific findings into four components: pollution and legal frameworks, ecosystem processes, scale-dependent effects, and innovative tools and methods. We conclude with challenges for the future, and identify the next steps needed for successful implementation of EBM in general and specifically for the Baltic Sea.     

Promise and performance of agricultural nutrient management policy: Lessons from the Baltic Sea

Following decades of international collaboration to restore the Baltic Sea, we provide an assessment of the domestic implementation of measures agreed to limit diffuse agricultural pollution and the patterns of policy instruments applied. Despite the Helsinki Convention being unusually specific in detailing what measures countries should introduce, we find many shortcomings. These are most pronounced in the larger countries (Poland, Germany and Russia), while smaller countries perform better, notably Sweden and Estonia. The patterns of policy instruments applied differ, influenced by domestic politics. The limited use of complementary policy instruments suggests that other priorities overrule full and effective implementation, with engagement mirroring the advantages that a restored Baltic Sea can bring to countries. Using the European Agricultural Fund for Rural Development to support farmers in managing nutrients, particularly advisory services and investments in modern manure management technologies, represents a significant opportunity for reducing agricultural pollution in most countries.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01549-3.     

Legal prerequisites for ecosystem-based management in the Baltic Sea area: The example of eutrophication

The purpose of this paper is to discuss the role of law in the management of the Baltic Sea, with focus on eutrophication. It aims to identify legal instruments or structures realizing an ecosystem approach. This also includes a discussion of the prerequisites of law as contributor to ecosystem-based management (EBM), as well as evaluation of current legal instruments. While ecosystem approach to environmental management is central to contemporary environmental management policy, it is still unclear what such an approach entails in concrete legal terms. The scope of the analysis stretches from international and EU legal regimes, to implementation and regulation within the national legal systems. A conclusion is that the management structures need further development to properly realize EBM, for example, through concretization of management measures, and clarification of duties and responsibilities for their realization.     

Reduction of Baltic Sea Nutrient Inputs and Allocation of Abatement Costs Within the Baltic Sea Catchment

The Baltic Sea Action Plan (BSAP) requires tools to simulate effects and costs of various nutrient abatement strategies. Hierarchically connected databases and models of the entire catchment have been created to allow decision makers to view scenarios via the decision support system NEST. Increased intensity in agriculture in transient countries would result in increased nutrient loads to the Baltic Sea, particularly from Poland, the Baltic States, and Russia. Nutrient retentions are high, which means that the nutrient reduction goals of 135 000 tons N and 15 000 tons P, as formulated in the BSAP from 2007, correspond to a reduction in nutrient loadings to watersheds by 675 000 tons N and 158 000 tons P. A cost-minimization model was used to allocate nutrient reductions to measures and countries where the costs for reducing loads are low. The minimum annual cost to meet BSAP basin targets is estimated to 4.7 billion €.     

Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea

Eutrophication of the Baltic Sea has potentially increased the frequency and magnitude of cyanobacteria blooms. Eutrophication leads to increased sedimentation of organic material, increasing the extent of anoxic bottoms and subsequently increasing the internal phosphorus loading. In addition, the hypoxic water volume displays a negative relationship with the total dissolved inorganic nitrogen pool, suggesting greater overall nitrogen removal with increased hypoxia. Enhanced internal loading of phosphorus and the removal of dissolved inorganic nitrogen leads to lower nitrogen to phosphorus ratios, which are one of the main factors promoting nitrogenfixing cyanobacteria blooms. Because cyanobacteria blooms in the open waters of the Baltic Sea seem to be strongly regulated by internal processes, the effects of external nutrient reductions are scale-dependent. During longer time scales, reductions in external phosphorus load may reduce cyanobacteria blooms; however, on shorter time scales the internal phosphorus loading can counteract external phosphorus reductions. The coupled processes inducing internal loading, nitrogen removal, and the prevalence of nitrogen-fixing cyanobacteria can qualitatively be described as a potentially self-sustaining "vicious circle." To effectively reduce cyanobacteria blooms and overall signs of eutrophication, reductions in both nitrogen and phosphorus external loads appear essential.     

A North Sea and Baltic Sea Model Ensemble Eutrophication Assessment

A method to combine observations and an ensemble of ecological models is suggested to produce a eutrophication assessment. Using threshold values and methodology from the Oslo and Paris Commissions (OSPAR) and the Helsinki Commission (HELCOM), four models are combined to assess eutrophication for the Baltic and North Seas for the year 2006. The assessment indicates that the entire southeastern part of the North Sea, the Kattegat, the Danish Straits, the Gulf of Finland, and the Gulf of Riga as well as parts of the Arkona Basin, the Bornholm Basin, and the Baltic proper may be classified as problem areas. The Bothnian Bay and parts of the Baltic proper, the Bornholm Basin, and the Arkona Basin are classified as potential problem areas. This method is a useful tool for the classification of eutrophication; however, the results depend on the threshold values, and further work is needed within both OSPAR and HELCOM to harmonize these values.     

Ecology,evolution, and management strategies of northern pike populations in the Baltic Sea

Baltic Sea populations of the northern pike (Esox lucius) have declined since the 1990s, and they face additional challenges due to ongoing climate change. Pike in the Baltic Sea spawn either in coastal bays or in freshwater streams and wetlands. Pike recruited in freshwater have been found to make up about 50 % of coastal pike stocks and to show natal homing, thus limiting gene flow among closely located spawning sites. Due to natal homing, sub-populations appear to be locally adapted to their freshwater recruitment environments. Management actions should therefore not involve mixing of individuals originating from different sub-populations. We offer two suggestions complying with this advice: (i) productivity of extant freshwater spawning populations can be boosted by modifying wetlands such that they promote spawning and recruitment; and (ii) new sub-populations that spawn in brackish water can potentially be created by transferring fry and imprinting them on seemingly suitable spawning environments.     

A Multivariate Baltic Sea Environmental Index

Since 2001/2002, the correlation between North Atlantic Oscillation index and biological variables in the North Sea and Baltic Sea fails, which might be addressed to a global climate regime shift. To understand inter-annual and inter-decadal variability in environmental variables, a new multivariate index for the Baltic Sea is developed and presented here. The multivariate Baltic Sea Environmental (BSE) index is defined as the 1st principal component score of four z-transformed time series: the Arctic Oscillation index, the salinity between 120 and 200 m in the Gotland Sea, the integrated river runoff of all rivers draining into the Baltic Sea, and the relative vorticity of geostrophic wind over the Baltic Sea area. A statistical downscaling technique has been applied to project different climate indices to the sea surface temperature in the Gotland, to the Landsort gauge, and the sea ice extent. The new BSE index shows a better performance than all other climate indices and is equivalent to the Chen index for physical properties. An application of the new index to zooplankton time series from the central Baltic Sea (Latvian EEZ) shows an excellent skill in potential predictability of environmental time series.     

The environmental regime of the Baltic Sea

This paper explains the transition and selection of environmental regimes, from the general framework of the regime in question, its evolution over time, and primary national approaches to the regime. We evaluate the significance of the environmental problems covered by the international regime for the countries concerned and the importance of problem-solving at the international level, and we assess national interests and approaches towards problem-solving and participation in the regime, especially their dynamics and changes in the period of transition.     

Ecological connectivity of the marine protected area network in the Baltic Sea,Kattegat and Skagerrak: Current knowledge and management needs

Marine protected areas (MPAs) have become a key component of conservation and fisheries management to alleviate anthropogenic pressures. For MPA networks to efficiently promote persistence and recovery of populations, ecological connectivity, i.e. dispersal and movement of organisms and material across ecosystems, needs to be taken into account. To improve the ecological coherence of MPA networks, there is hence a need to evaluate the connectivity of species spreading through active migration and passive dispersal. We reviewed knowledge on ecological connectivity in the Baltic Sea, Kattegat and Skagerrak in the northeast Atlantic and present available information on species-specific dispersal and migration distances. Studies on genetic connectivity are summarised and discussed in relation to dispersal-based analyses. Threats to ecological connectivity, limiting dispersal of populations and lowering the resilience to environmental change, were examined. Additionally, a review of studies evaluating the ecological coherence of MPA networks in the Baltic Sea, Kattegat and Skagerrak was performed, and suggestions for future evaluations to meet management needs are presented.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01684-x.     

Arsenic in sediments from the southeastern Baltic Sea

Arsenic occurs as a persistent constituent in many of the chemical weapons dumped into the Baltic Sea; it can be used as an indicator of leakage and dispersal of released munitions to the marine environment. Total arsenic was analysed in sediment samples taken from the Lithuanian economic zone in the Baltic Sea, which included samples from the chemical munitions dumpsite in the Gotland Basin and national monitoring stations in the southeastern Baltic Sea. Arsenic concentrations in sediments ranged from 1.1 to 19.0 mg kg(-1), with an average of 3.4 mg kg(-1). Although there was evidence of slightly elevated arsenic content in sediments near the weapons dumpsite, arsenic concentrations were nevertheless quite low relative to other investigations in the Baltic and North Seas.     

Climate Warming and Pikeperch Year-Class Catches in the Baltic Sea

Climate change scenarios concerning the Baltic Sea predict increase in surface water temperatures. Pikeperch (Sander lucioperca (L.)) inhabits the coastal areas of the northern Baltic Sea and is an important fish species for the Finnish fisheries. The year-class strength of pikeperch varies strongly between years and significantly depends on water temperature. We aimed to study the effects of changing temperature conditions on pikeperch fisheries and distribution based on commercial catch data from the period 1980–2008 in the Finnish coastal areas of the Baltic Sea. The results indicated that warmer summers will produce stronger pikeperch year-classes that consequently contribute significantly to the future catches. The average temperature in June–July explained 40% of the variation in the year-class catches in the Gulf of Finland and 73% in July–August in the Archipelago Sea. During the study period, the distribution of pikeperch catches expanded toward north along the coasts of the Bothnian Sea.     

Echoes from the Past: A Healthy Baltic Sea Requires More Effort

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.     

Framing Environmental Risks in the Baltic Sea: A News Media Analysis

Scientific complexity and uncertainty is a key challenge for environmental risk governance and to understand how risks are framed and communicated is of utmost importance. The Baltic Sea ecosystem is stressed and exposed to different risks like eutrophication, overfishing, and hazardous chemicals. Based on an analysis of the Swedish newspaper Dagens Nyheter, this study discusses media representations of these risks. The results show that the reporting on the Baltic Sea has been fairly stable since the beginning of the 1990s. Many articles acknowledge several risks, but eutrophication receives the most attention and is also considered the biggest threat. Authorities, experts, organizations, and politicians are the dominating actors, while citizens and industry representatives are more or less invisible. Eutrophication is not framed in terms of uncertainty concerning the risk and consequences, but rather in terms of main causes.     

Modeling riverine nutrient transport to the Baltic Sea: a large-scale approach

We developed for the first time a catchment model simulating simultaneously the nutrient land-sea fluxes from all 105 major watersheds within the Baltic Sea drainage area. A consistent modeling approach to all these major watersheds, i.e., a consistent handling of water fluxes (hydrological simulations) and loading functions (emission data), will facilitate a comparison of riverine nutrient transport between Baltic Sea subbasins that differ substantially. Hot spots of riverine emissions, such as from the rivers Vistula, Oder, and Daugava or from the Danish coast, can be easily demonstrated and the comparison between these hot spots, and the relatively unperturbed rivers in the northern catchments show decisionmakers where remedial actions are most effective to improve the environmental state of the Baltic Sea, and, secondly, what percentage reduction of riverine nutrient loads is possible. The relative difference between measured and simulated fluxes during the validation period was generally small. The cumulative deviation (i.e., relative bias) [Sigma(Simulated - Measured)/Sigma Measured x 100 (%)] from monitored water and nutrient fluxes amounted to +8.2% for runoff, to -2.4% for dissolved inorganic nitrogen, to +5.1% for total nitrogen, to +13% for dissolved inorganic phosphorus and to +19% for total phosphorus. Moreover, the model suggests that point sources for total phosphorus compiled by existing pollution load compilations are underestimated because of inconsistencies in calculating effluent loads from municipalities.     

Polychlorinated biphenyls and organochlorine pesticides in Baltic Sea sediments and bivalves

Insecticide resistance is an evolutionary response to insecticides and, as such, important for environmental biomonitoring and for pest management. Fitness disadvantage in the absence of insecticide is a frequent assumption in models of insecticide resistance evolution, which was observed in different insect species. Fitness studies are based in demographic performance of isolated populations without direct interaction between insecticide-resistant and -susceptible populations. Here we reported a study of direct competition following a factorial bivariate design between an insecticide-susceptible population of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), and one of two insecticide-resistant populations - one exhibiting fitness disadvantage based on demographic studies (Juiz de Fora) and other not exhibiting it (Jacarezinho). Total number of insects, mortality by insecticide, insect body mass and respiration rate were recorded after three generations of competition. Indeed, fitness disadvantage was observed in the resistant population from Juiz de Fora, but not in the population from Jacarezinho, as expected. The higher body mass and respiration rate of the insecticide-resistant insects from Jacarezinho are probably mitigating the physiological costs associated with the insecticide resistance minimizing their fitness disadvantage, what does not take place with the insecticide-resistant insects from Juiz de Fora. These distinct responses between the insecticide-resistant populations are probably related to the length and intensity of field-selection with insecticides.