Baltic Sea Case Study Research Articles

Ecosystem-based fisheries management increases catch and carbon sequestration through recovery of exploited stocks: The western Baltic Sea case study

Legal requirement in Europe asks for Ecosystem-Based Fisheries Management (EBFM) in European seas, including consideration of trophic interactions and minimization of negative impacts of fishing on food webs and ecosystem functioning. This study presents the first mass-balanced ecosystem model focused on the western Baltic Sea (WBS). Results show that heavy fishing pressure exerted on the WBS has forced top predators such as harbour porpoise and cod to cover their dietary needs by shifting from forage fish to other prey or find food outside of the model area. The model was then developed to explore the dynamics of four future fishery scenarios: (1) business as usual (BAU), (2) maximum sustainable fishing (F = FMSY), (3) half of FMSY, and (4) EBFM with F = 0.5 FMSY for forage fish and F = 0.8 FMSY for other fish. Simulations show that BAU would perpetuate low catches from depleted stocks with a high risk of extinction for harbour porpoise. In contrast, the EBFM scenario would allow the recovery of harbour porpoise, forage fish and cod with increases in catch of herring and cod. EBFM promotes ecosystem resilience to eutrophication and ocean warming, and through the rebuilding of commercial stocks increases by more than three times carbon sequestration compared to BAU. The model provides an interrelated assessment of trophic guilds in the WBS, as required by European law to assess whether European seas are in good environmental status.

Developing a conceptual influence diagram for socio-eco-technical systems analysis of biofouling management in shipping – A Baltic Sea case study

Ship hulls create a vector for the transportation of harmful non-indigenous species (NIS) all over the world. To sustainably prevent NIS introductions, the joint consideration of environmental, economic and social aspects in the search of optimal biofouling management strategies is needed. This article presents a multi-perspective soft systems analysis of the biofouling management problem, based on an extensive literature review and expert knowledge collected in the Baltic Sea area during 2018–2020. The resulting conceptual influence diagram (CID) reveals the multidimensionality of the problem by visualizing the causal relations between the key elements and demonstrating the entanglement of social, ecological and technical aspects. Seen as a boundary object, we suggest the CID can support open dialogue and better risk communication among stakeholders by providing an illustrative and directly applicable starting point for the discussions. It also provides a basis for quantitative management optimization in the future.

Valuating environmental impacts from ship emissions – The marine perspective

Shipping is an activity responsible for a range of different pressures affecting the marine environment, air quality and human welfare. The methodology on how ship emissions impact air quality and human health are comparatively well established and used in cost-benefit analysis of policy proposals. However, the knowledge base is not the same for impacts on the marine environment and a coherent environmental and socio-economic impact assessment of shipping has not yet been made. This risk policies to be biased towards air pollution whilst trading off impacts on the marine environment. The aim of the current study was to develop a comprehensive framework on how different pressures from shipping degrade marine ecosystems, air quality and human welfare. A secondary aim was to quantify the societal damage costs of shipping due to the degradation of human welfare in a Baltic Sea case study. By adding knowledge from marine ecotoxicology and life-cycle analysis to the existing knowledge from climate, air pollution and environmental economics we were able to establish a more comprehensive conceptual framework that allows for valuation of environmental impacts from shipping, but it still omits economic values for biological pollution, littering and underwater noise. The results for the Baltic Sea case showed the total annual damage costs of Baltic Sea shipping to be 2.9 billion €2010 (95% CI 2.0–3.9 billion €2010). The damage costs due to impacts on marine eutrophication (768 million €2010) and marine ecotoxicity (582 million €2010) were in the same range as the total damage costs associated with reduced air quality (816 million €2010) and climate change (737 million €2010). The framework and the results from the current study can be used in future socio-economic assessments of ship emissions to prioritize cost efficient measures. The framework can be used globally but the damage costs presented on the marine environment are restricted to emissions on the Baltic Sea and Kattegat region as they are based on willingness to pay studies conducted on citizens around the Baltic Sea where eutrophication and emissions of chemicals are particularly threats to the state of the Baltic Sea.

Wave height return periods from combined measurement–model data: a Baltic Sea case study

Abstract. This paper presents how to account for the lack of sampling variability in model data when they are combined with wave measurements. We addressed the dissimilarities between the types of data by either (i) low-pass filtering the observations or (ii) adding synthetic sampling variability to the model. Measurement–model times series combined with these methods served as the basis for return period estimates of a high wave event in January 2019. During this storm northerly wind speeds in the Baltic Sea rose to 32.5 m s−1 and an unprecedented significant wave height of 8.1 m was recorded in the Bothnian Sea sub-basin. Both methods successfully consolidated the combined time series but produced slightly different results: using low-pass-filtered observations gave lower estimates for the return period than using model data with added sampling variability. Extremes in both types of data followed the same type of theoretical distributions, and our best estimate for the return period was 104 years (95 % confidence 39–323 years). A similar wave event can potentially be more likely in the future climate, and this aspect was discussed qualitatively.

Submarine groundwater discharge as a source of pharmaceutical and caffeine residues in coastal ecosystem: Bay of Puck, southern Baltic Sea case study

Even though the occurrence of pharmaceuticals in the water environment is thought to be a potential problem for human health and aquatic organisms, the level of knowledge of their sources and presence in the marine ecosystem is still insufficient. Therefore, this study was designed to determine the emergence of sixteen pharmaceuticals and caffeine in groundwater, submarine groundwater discharge (SGD), rivers and coastal seawater in the southern Baltic Sea. It has been recognized that chemical substances load associated with SGD can affect coastal ecosystems equally or even greater than surface runoff. Hence, the Bay of Puck, which is an active groundwater discharge area, has been chosen as a model study site to assess the preliminary risk of pharmaceutical and caffeine residues supply in coastal ecosystem. A special focus was placed on tracing the possible sources of pollution for groundwater and SGD based on the composition of collected samples. Five pharmaceuticals (carbamazepine, sulfapyridine, sulfamethoxazole, ketoprofen and diclofenac) and caffeine were detected in varying concentrations from below the detection limit to 1528.2 ng L−1. Caffeine and diclofenac were the most widespread compounds. Groundwater was mostly enriched in the analysed compounds and consequently SGD has been recognized as an important source of identified pharmaceutical and caffeine residues to the Bay of Puck. A predicted no-effect concentration (PNEC) was determined in order to perform an environmental risk assessment of five pharmaceuticals and caffeine detected in water samples. Finally, future challenges and potential amendments in monitoring strategies are discussed.

Characterising the relaxation distance of nearshore submarine morphology: A southern Baltic Sea case study

A method for defining the length of coast with alongshore uniformity of nearshore submarine morphology is required in many shore-normal, nearshore profile modelling approaches. Here, we introduce a new variable, the ‘relaxation distance’, to describe the alongshore spacing between two adjacent shore-normal profiles characterised by distinct morphologies. Within this distance, alongshore morphological changes are too small to distinguish, so the nearshore submarine morphology is regarded as uniform along the coast. We apply a semi-variogram approach, which expresses decreased spatial correlation of the nearshore submarine morphology with alongshore distance, to quantify relaxation distances. We apply this morphological variable to analyse 225 measured shore-normal submarine profiles at 500 m intervals in three distinct sites of the tideless, wave-dominated southern Baltic coast: Swina, Łeba, and Hel. The relaxation distances of these three sites are approximately 4500 m, 3000 m, and 2200 m. Of the three sites, Swina has the smoothest nearshore submarine morphology and the weakest wave energy. The relaxation distances of different quasi-straight segments at each site appear similar but those at different sites decrease with enlarged morphological perturbations, which are residuals resulting from detrending the shore-normal profiles. The standard deviations of these morphological perturbations are correlated with the incidence wave angles and wave energy. We also found that large perturbations (such as longshore bars and channels) have a significant impact on the estimation of underwater volume using shore-normal profile trends. Therefore, relaxation distance can indicate morphological smoothness, the length of shore-parallel uniform nearshore submarine morphology, and the impact of local processes on submarine morphology.

Risk assessment for exemptions from ballast water management – The Baltic Sea case study

The International Convention for the Control and Management of Ship’s Ballast Water and Sediments sets requirements to prevent organism transfers. Vessels on certain routes can be exempted from such requirements based on risk assessment (RA). As the convention nears its entry into force, the interest in exemptions increases. Such RA should be conducted according to the International Maritime Organization G7 Guidelines. We present a RA study for exemptions applied to intra-Baltic shipping considering different RA methods, i.e., environmental matching, species specific method including target species and species biogeographical aspects. As reliable species data in the ports considered are unavailable and following the precautionary principle, no exemptions should be granted. To ensure data reliability, port baseline surveys and regular monitoring programs should be undertaken during the exemption period as new species found influence the RA result. The RA model prepared is considered as of value to other areas worldwide.

Large spatial variations in coastal <sup>14</sup>C reservoir age – a case study from the Baltic Sea

Abstract. Coastal locations are highly influenced by input from freshwater river runoff, including sources of terrestrial carbon, which can be expected to modify the 14C reservoir age, or R (t), associated with marine water. In this Baltic Sea case study, pre-bomb museum collection mollusc shells of known calendar age, from 30 locations across a strategic salinity transect of the Baltic Sea, were analysed for 14C, δ13C and δ18O. R (t) was calculated for all 30 locations. Seven locations, of which six are within close proximity of the coast, were found to have relatively higher R (t) values, indicative of hard-water effects. Whenever possible, the Macoma genus of mollusc was selected from the museum collections, in order to exclude species specific reservoir age effects as much as possible. When the Macoma samples are exclusively considered, and samples from hard-water locations excluded, a statistically significant correlation between Macoma R (t) and average salinity is found, indicating a two end-member linear mixing model between 14Cmarine and 14Crunoff. A map of Baltic Sea Macoma aragonite R (t) for the late 19th and early 20th centuries is produced. Such a map can provide an estimate for contemporary Baltic Sea Macoma R (t), although one must exercise caution when applying such estimates back in time or to 14C dates obtained from different sample material. A statistically significant correlation is found between δ18Oaragonite and Macoma R (t), suggesting that δ18Oaragonite can be used to estimate Macoma palaeo-R (t), due to the δ18Oaragonite signal being dominated by the salinity gradient of the Baltic Sea. A slightly increased correlation can be expected when δ18Oaragonite is corrected for temperature fractionation effects. The results of this Baltic Sea case study, which show that R (t) is affected by hydrographic conditions and local carbon inputs, have important consequences for other coastal and estuarine locations, where R (t) is also likely to significantly vary on spatial and temporal bases.

Management measures and fishers' commitment to sustainable exploitation: a case study of Atlantic salmon fisheries in the Baltic Sea

Fisheries management aimed at sustainable exploitation may affect fish populations indirectly by influencing human behaviour. We propose a methodology that includes stakeholders’ opinions, perceptions, and resulting behaviour, within assessment models designed to evaluate the impact of different management measures on the stocks. Based on interviews and a questionnaire, we use a Bayesian belief network to examine which factors determine fishers’ commitment to sustainable fisheries goals, what impact commitment has on exploitation rate, and what measures can be taken to improve commitment. In addition to exploring alternative management measures, the analysis evaluates knowledge actions (providing information to fishers) and commitment actions (intended to increase trust, consensus, and cooperation). The method is applied in a Baltic Sea case study in which commitment is important for successful recovery of Atlantic salmon (Salmo salar) stocks. The results indicate that the more fishers rely on fishing as their source of income, the less is their commitment and the smaller is the impact of changes in commitment on subsequent catches. The results suggest that commitment can be improved by selecting management measures favoured by fishers and by combining them with commitment and knowledge actions.

Feasibility of hyperspectral remote sensing for mapping benthic macroalgal cover in turbid coastal waters—a Baltic Sea case study

Quantitative analysis of coastal marine benthic communities enables to adequately estimate the state of coastal marine environment, provide better evidence for environmental changes and describe processes that are conditioned by anthropogenic forces. Remote sensing could provide a tool for mapping bottom vegetation if the substrates are spectrally resolvable. We measured reflectance spectra of green ( Cladophora glomerata), red ( Furcellaria lumbricalis), and brown ( Fucus vesiculosus) macroalgae and used a bio-optical model in estimating whether these algae distinguish optically from each other, from sandy bottom or deep water in turbid water conditions of the Baltic Sea. The simulation was carried out for three different water types: (1) CDOM-rich coastal water, (2) coastal waters not directly impacted by high CDOM discharge from rivers but with high concentration of cyanobacteria, (3) open Baltic waters. Our modelling results indicate that the reflectance spectra of C. glomerata, F. lumbricalis, F. vesiculosus differ from each other and also from sand and deep water reflectance spectra. The differences are detectable by remote sensing instruments at spectral resolution of 10 nm and SNR better than 1000:1. Thus, the lowest depth limits where the studied macroalgae grow do not exceed the depth where such remote sensing instruments could potentially detect the spectral differences between the studied species.

Predation on newly settled bivalves by deposit-feeding amphipods:a Baltic Sea case study

In the Baltic Sea, predation on postlarvae of the infaunal clam Macoma balthlca by adults of the 2 most abundant depos~t-feeding amphipods, Monoporeia affinis and Pontoporeia femorata, has been considered to be a crucial factor in determining the bivalve's recruitment success The functional response of adult M. affjnis to postlarvae of the bivalve was shown in laboratory exper~rnents to be type 111-like, with no levelling off of the number of prey consumed per predator within the postlarval densities tested. Densities included were higher than the highest reported from habitats where both species occur together. In laboratory experiments, adults of P. femorata were also shown to kill M. balthica postlarvae. In neither amphipod species did adults select among sizes of newly settled M. balthica. Juvenile M. affinis were likewise found to kill M. balthica postlarvae. Our results, and a recent field study, confirm the effect of the amphipods on M. balthica postlarvae and their role in controlling bivalve recruitment in Baltic soft sediments. They also support the idea that interactions among juveniles of macrofauna may affect the recruitment success of many benthic specles and therefore be important in structuring benthic communities.

Dissipation and mixing in a coastal jet: A Baltic Sea case study

Vertical profiles of dissipation rate are used to study mixing properties within a shallow water region influenced by a coastal jet.¶In the upper 10-m layer dissipation rates of the order of ɛ∝ 10-6 W kg-1 have been measured. Most dissipation results from local production of turbulent kinetic energy, caused by Reynolds-stress in the coastal jet. Some high-energetic turbulent events are not locally balanced and are most probably advected to the measurement site by the coastal jet.¶Estimates of the associated eddy diffusivities for locally balanced situations are in the order of Kρ∝ 10-4 m2 s-1. This comparably high value is due to the high level of turbulence throughout the water column and high mixing intensity (γmix≈ 0.22). This feature is clearly related to the coastal jet in its stratified environment.