Baltic Sea Area Research Articles

Multi-year gradient measurements of sea spray fluxes over the Baltic Sea and the North Atlantic Ocean

Abstract. Ship-based measurements of sea spray aerosol (SSA) gradient fluxes in the size range of 0.5–47 µm in diameter were conducted between 2009–2017 in both the Baltic Sea and the North Atlantic Ocean. Measured total SSA fluxes varied between 8.9 × 103 ± 6.8 × 105 m−2 s−1 for the Baltic Sea and 1.0 × 104 ± 105 m−2 s−1 for the Atlantic Ocean. The analysis uncovered a significant decrease (by a factor of 2.2 in the wind speed range of 10.5–14.5 m s−1) in SSA fluxes, with chlorophyll a (chl a) concentration higher than 3.5 mg m−3 in the Baltic Sea area. We found statistically significant correlations for both regions of interest between SSA fluxes and various environmental factors, including wind speed, wind acceleration, wave age, significant wave height, and wave Reynolds number. Our findings indicate that higher chl a concentrations are associated with reduced SSA fluxes at higher wind speeds in the Baltic Sea, while the influence of wave age showed higher aerosol emissions in the Baltic Sea for younger waves compared to the Atlantic Ocean. These insights underscore the complex interplay between biological activity and physical dynamics in regulating SSA emissions. Additionally, in both measurement regions, we observed weak correlations between SSA fluxes and air and water temperature and between SSA fluxes and atmospheric stability. Comparing the Baltic Sea and the North Atlantic, we noted distinct emission behaviors, with higher emissions in the Baltic Sea at low wave age values compared to the Atlantic Ocean. This study represents the first comparative analysis of SSA flux measurements using the same methodology in these contrasting marine environments.

Temperature, sediment resuspension, and salinity drive the prevalence of Vibrio vulnificus in the coastal Baltic Sea

ABSTRACT The number of Vibrio -related infections in humans, e.g., by Vibrio vulnificus , has increased along the coasts of the Baltic Sea. Due to climate change, vibriosis risk is expected to increase. It is, therefore, pertinent to design a strategy for mitigation of the vibriosis threat in the Baltic Sea area, but a prerequisite is to identify the environmental conditions promoting the occurrence of pathogenic Vibrio spp., like V. vulnificus . To address this, we sampled three coastal Baltic sites in Finland, Germany, and Denmark with salinities between 6 and 21 from May to October 2022. The absolute and relative abundances of Vibrio spp. and V. vulnificus in water were compared to environmental conditions, including the presence of the eelgrass Zostera marina , which has been suggested to reduce pathogenic Vibrio species abundance. In the water column, V. vulnificus only occurred at the German station between July and August at salinity 8.1–11.2. Temperature and phosphate (PO 4 3– ) were identified as the most influencing factors for Vibrio spp. and V. vulnificus . The accumulation of Vibrio spp. in the sediment and the co-occurrence with sediment bacteria in the water column indicate that sediment resuspension contributed to V. vulnificus abundance. Interestingly, V. vulnificus co-occurred with specific cyanobacteria taxa, as well as specific bacteria associated with cyanobacteria. Although we found no reduction in Vibrio spp. or V. vulnificus associated with eelgrass beds, our study underscores the importance of extended heatwaves and sediment resuspension, which may elevate the availability of PO 4 3– , for Vibrio species levels at intermediate salinities in the Baltic Sea. IMPORTANCE Elevated sea surface temperatures are increasing the prevalence of pathogenic Vibrio at higher latitudes. The recent increase in Vibrio -related wound infections and deaths along the Baltic coasts is, therefore, of serious health concern. We used culture-independent data generated from three Baltic coastal sites in Denmark, Germany, and Finland from May to October (2022), with a special focus on Vibrio vulnificus , and combined it with environmental data. Our temporal model shows that temperature, combined with sediment resuspension, drives the prevalence of V. vulnificus at intermediate salinities in the coastal Baltic Sea.

Coastal flooding in Kołobrzeg (Kolberg) area, southern Baltic Sea, in the light of historical and geological data

The Baltic Sea is not a typical tsunami area, but there are reports of coastal flooding, with its traces preserved in deposits from Germany, Finland and Sweden, and more recently from Poland. In this study an attempt was made to verify historical and legendary accounts of the ‘Sea Bear’ (‘der Seebär’) phenomenon. In the descriptions of folk accounts, the phenomenon has the features such as suddenness, speed, short duration, independence from the atmospheric conditions on land and sea. The search for coastal flooding deposits was conducted around the town of Kołobrzeg (Kolberg), located on the southern coast of the Baltic Sea. For the study area in chronicle record exist information about two events (17 September 1497 and 1 March 1779). For both events no record has been found in geological profiles, probably due to strong anthropogenic transformation of the subsurface layers. However there is quite precise information from chronicle records on the extent of the event from 17 September 1497 and on the thickness of the sandy layer left by the flooding. Based on this information in the Kołobrzeg area the range of the sand layer was 1400 m from the seashore, and its thickness locally reached approximately 10 cm. The flood height estimated according to the above-presented assumptions was 4.9 m a.s.l. In the Baltic Sea area, coastal flooding is possibly due to atmospheric forcing which can be responsible for an external waves event and devastating long waves, which have the same spatial and temporal scale as typical tsunami waves.

Sustainable Methods of Soybean Cultivation in Poland

Many countries in Europe are struggling with a shortage of feed protein; moreover, efforts are being made to limit the import of post-extraction soybean meal, most often from GMO crops. To achieve the above assumptions, varietal progress is necessary and, above all, breeding work should aim at greater adaptation to regional conditions. This study was designed to evaluate the potential for growing Ukrainian soybean ‘Annushka’ in the southeastern Baltic Sea area, in accordance with the application of mineral nitrogen fertilizer and the inoculation of seeds with Bradyrhizobium japonicum. Soybean ‘Annushka’ yielded 0.98–1.68 t ha−1 in the conditions of central Poland. Our experiments have shown significant variations in seed, protein, and fat yields over the years. The maximum amounts of these characteristics were recorded in 2017. Nitrogen fertilization combined with seed inoculation with B. japonicum has proven to be an important factor in improving soybean yields; however, it slightly modified the content of organic compounds in seeds. Improvement in seed and protein yields relative to the control amounted, respectively, to Nitragina + 30 kg N ha−1 (58.8%; 72.6%), HiStick® Soy + 30 kg N ha−1 (57.6%; 68.3%), and Nitroflora + 60 kg N ha−1 (57.6%; 71.9%).

The first documented and characterized Norwegian acid sulfate soils

AbstractAcid sulfate soils (ASS) containing hypersulfidic material (pH >4) can, when drained, transform to ASS with a thionic horizon (pH <4), which can cause environmental effects due to the formation of sulfuric acid and the consequent mobilization and leaching of metals and acid into waterways, as well as cause geotechnical problems. Yet, the occurrence of ASS has till now not been a topic of research in Norway. The present pilot study was carried out on an area along the northern coast of Norway. Thirty‐nine localities were sampled and analysed near Alta. Of these, six were classified as ASS with either hypersulfidic or parahypersulfidic material. ASS is not as widespread as within the Baltic Sea area, but the analyses document the occurrence of ASS with hypersulfidic material with high acidifying potential in certain areas if oxidized. This pilot study shows that ASS occurs in specific areas. Three localities with documented ASS were studied in greater detail. Here, sections were excavated and analysed to help with the understanding of the geological context of these occurrences. In this way, the geological prerequisites considered of importance of soils with ASS with hypersulfidic material are outlined. The prerequisites for ASS occurrence that evolved during this study include young, marine, fine‐grained deposits and a low relief environment subjected to episodic sedimentation but otherwise calm water and little water exchange. The results are a starting point for further studies of ASS occurrences along the Norwegian coast.

Effect of fuel prices on sailing speeds in short-sea shipping

ABSTRACT In this paper, we estimate fuel price elasticities of sailing speed for general cargo vessels using data covering the Baltic Sea and Norwegian coastal areas during the years 2007–2018. To disentangle the correlation between fuel prices and freight rates arising from changes in global demand, we instrument fuel prices on price changes triggered by supply shocks. The shocks are derived from the structural vector autoregressive (SVAR) model proposed by Kilian (2009). In a sensitivity analysis, we use unanticipated oil supply shocks derived from oil supply outages as an alternative instrument for fuel prices. We find that disregarding the correlation between fuel prices and freight rates yields biased parameter estimates, which can partly explain the mixed results in the previous literature. Our preferred estimate for the fuel price elasticity of speed is −0.08.

Strong economic incentives of ship scrubbers promoting pollution

In response to stricter regulations on ship air emissions, many shipowners have installed exhaust gas cleaning systems, known as scrubbers, allowing for use of cheap residual heavy fuel oil. Scrubbers produce large volumes of acidic and polluted water that is discharged to the sea. Due to environmental concerns, the use of scrubbers is being discussed within the International Maritime Organization. Real-world simulations of global scrubber-vessel activity, applying actual fuel costs and expenses related to scrubber operations, show that 51% of the global scrubber-fitted fleet reached economic break even by the end of 2022, with a surplus of €4.7 billion in 2019 euros. Within five years after installation, more than 95% of the ships with the most common scrubber systems reach break even. However, the marine ecotoxicity damage cost, from scrubber water discharge in the Baltic Sea Area 2014–2022, amounts to >€680 million in 2019 euros, showing that private economic interests come at the expense of marine environmental damage.

Advances and prerequisites for strontium isotope analyses through laser ablation in an aquatic context – Targeting Mid-Neolithic Baltic Sea harp seal (Pagophilus groenlandicus) mobility and breeding grounds

Harp seals (Phoca groenlandicus), once present in the Baltic Sea, now stand extinct. During the Middle Neolithic period, they held significant dietary importance for the Pitted Ware Culture hunter-fisher-gatherers in Scandinavia. Because they are no longer available for ecological studies, little is known about their specific behavioural intricacies, such as diet, mobility, and reproductive strategies. Because of the seal's pivotal role in these human societies and because they provide an interesting ecological case study on post-isolation ecological adaptation to new environmental conditions, a comprehensive investigation into Baltic Sea harp seal behaviour is warranted.In this pursuit, we employ sequential analysis of strontium isotope ratios (87Sr/86Sr) in harp seal teeth sourced from archaeological contexts across three study regions. This data is harmonized with osteometric analyses from fifteen archaeological sites from the Baltic Sea area, establishing a methodological framework for comprehending the Sr isotopic pathway in a brackish water inland sea. By adopting this approach, we unveil breeding and mobility patterns of the long-extinct Baltic Sea harp seals, approximate specific breeding areas connected to each group of seals and delve into the ontogenic temporal frame governing these observed patterns. This endeavour culminates in an enriched understanding of the adaptive behaviours exhibited by Baltic Sea harp seals and equips us with the insights necessary to decipher the lifestyle of the human societies intricately intertwined with them.

Thiamine Deficiency M74 Developed in Salmon (Salmo salar) Stocks in Two Baltic Sea Areas after the Hatching of Large Year-Classes of Two Clupeid Species—Detected by Fatty Acid Signature Analysis

Lipid-related thiamine (vitamin B1) deficiency of Baltic salmon (Salmo salar), the M74 syndrome, is generally caused by feeding on abundant young sprat (Sprattus sprattus) in the Baltic Proper, the main foraging area of these salmon. In 2014, a strong year-class of sprat was hatched in the Baltic Proper, and a strong herring (Clupea harengus) year-class was hatched in the Gulf of Bothnia, where herring is the dominant salmon prey. The fatty acid (FA) signatures of prey fish in muscle or eggs of second sea-year spawners suggested that 27% of wild River Simojoki and 68% of reared River Dal salmon remained in the Gulf of Bothnia in 2014 instead of continuing to the Baltic Proper. In 2016, 23% of the M74 females of the River Simojoki and 58% of the River Dal originated from the Gulf of Bothnia, and 13% and 16%, respectively, originated from the Baltic Proper. Some salmon from the River Neris in the southern Baltic Proper had also been feeding in the Gulf of Bothnia. In general, low free thiamine (THIAM) concentration in eggs was associated with high lipid content and high docosahexaenoic acid (DHA, 22:6n−3) and n−3 polyunsaturated FA (n−3 PUFA) concentrations in muscle but not in eggs. A higher THIAM concentration and lower proportions of DHA and n−3 PUFAs in Arctic Ocean salmon eggs, despite higher egg lipid content, indicated that their diet contained fewer fatty fish than the Baltic salmon diet. Hence, M74 originated by foraging heavily on young fatty sprat in the Baltic Proper or herring in the Gulf of Bothnia.

Near seafloor methane flux in the world's largest human-induced dead zone is regulated by sediment accumulation rate

The vast oxygen-depleted area of the central Baltic Sea is the largest human-induced dead zone in the world with 70,000 km2 or approximately three times the second largest one in the Gulf of Mexico. Methane occurs in high concentrations in bottom waters (3200 nM) and sediments (30 mM), and its dynamics is better constrained for the water column, but still poorly understood on sediments. Here we show that sediment accumulation rate plays a major role in regulating the quantity of organic matter and its residence time in the sulphate reduction and methanogenesis zones and, therefore, affects methane generation, consumption, and diffusive flux in sediments near the seafloor (< 1 m). High fluxes found in high sediment accumulation rate areas and competition for substrate (organoclastic sulphate reduction vs. anaerobic oxidation of methane with sulphate), compromise the ability of the thin microbial filter to consume and prevent methane diffusion through the seafloor.

Examining the performance of along-track multi-mission satellite altimetry – A case study for Sentinel-6

Abstract Satellite altimetry (SA) is one of the most valuable techniques that measure the sea level data at both the near-coast and offshore. There exists, however, multiple challenges and hindrances in determining and using accurate sea level data. The most pertinent is that evaluation of SA performance requires that all data sources (such as tide gauges (TG) and hydrodynamic models (HDMs)) refer to the same vertical datum. Thus, knowledge of the geoid (equipotential surface of the earth) is essential in linking different sources of sea level. Accordingly, this study examines performance of along-track data for three satellite missions (Sentinel-3A, Jason-3, and Sentinel-6A) to obtain realistic sea level variation and to determine the accuracy of the various missions in the complex area of the eastern Baltic Sea. The methodology consisted of utilizing SA, HDM, and TG data and a high-resolution geoid model. Results show that root-mean-square error (RMSE) varied for Jason-3 within a range of 1.68–50.14 cm, Sentinel 3A with a range of 2.8–46.27 cm, and Sentinel 6A with a range of 3.5–43.90 cm. Sentinel 6A was determined to be the most accurate and reliable satellite mission. Results also showed higher RMSE (15.7–46.2 cm) during (i) the seasonal sea ice month (e.g. March 2018); (ii) at locations of several islands (e.g. eastern section of Gulf); and (iii) at locations where rivers discharged into the Gulf (e.g. Nava, Kemi, Luga, and Neva rivers). These features tended to show up as peaks in the final results even though robust data processing for outliers were undertaken. These results suggests that improvements can still be made in the SA retrackers and also in the data-processing techniques utilized.

Knowledge co-production around the cormorant-fishing conflict using a joint fact-finding approach

The great cormorant (Phalacrocorax carbo) has been a persistent source of human–wildlife conflicts in the Baltic Sea area. Fishers have perceived cormorants as competitors for fish resources, while conservationists have resisted mass hunting of the birds. In this paper, we analyse the cormorant conflict in Finland, with a special focus on its factual dimensions and the previous attempts to address the conflict at the national and regional levels. We also present the results from a knowledge co-production process, structured as a joint fact-finding process to address the contested knowledge claims concerning cormorant-fishing interactions. The results suggest that the factual controversy about the cormorant effect on fishing livelihood is essentially a frame conflict resulting from different scales of analysis. Our findings support the assumption that knowledge co-production processes have the potential to address science-intensive environmental conflicts and create practically useful and contextually appropriate knowledge, which integrate scientific knowledge with place- and practice-based knowledge. The process developed a shared understanding of the fishers’ practical wildlife-induced problems and several other questions, including cormorant impacts on migratory fish in Finland. A key to generating shared information was that the participants had control over information used in the process. Furthermore, third-party facilitation was important to ensure effective dialogue. While interpersonal conflicts have not been the original source of the impasse, they have become an important part of it and prevented efforts to constructively address the conflict.

The applicability of ALARO and AROME wind-fields in multi-scale waves forecasting in open sea and coastal areas of the southern Baltic Sea

The main objective of the study was to implement the wave model in two independent systems fed respectively by wind fields with a 4 km resolution in the Baltic-wide area and a 2 km resolution in the shallow coastal regions of the southern Baltic for operational work. The study included the selection the best parameterization, which was carried out using measured data and model data from the verified SWAN-COSMO system. The chosen best parameterization of the model, including the time step, iteration, wind scaling, dispersion coefficients and swell formula, among others, allowed the identification of the optimal system that guarantees the most reliable predictions. The most reliable forecasts reproducing real conditions, both for the model powered by wind fields with a resolution of 4 km and 2 km, were obtained for the configuration characterized by the parameters: 30-min time step, 3 iterations, a wind scaling factor of 32 using DEBIAS equal to 0.89, coefficients related to local dissipation and cumulative of 2.8 × 10–6 and 3.5 × 10–5, respectively, and Ardhiun's swell formula of 1.20. The values of the correlation coefficient with both the measured data and the results of the comparative model for significant wave height and wave period, respectively, were no lower than: 0.95 and 0.73 (Petrobaltic) and 0.96 and 0.90 (Pomeranian Bay). Root mean square error (RMSE) values were <0.23 m and <0.20 s (Petrobaltic) and <0.20 m and <0.74 s (Pomeranian Bay) for significant wave height and mean wave period, respectively. Analysis of the forecast results showed some limitations in using the mesoscale model in coastal areas, and the solution was to use the high-resolution model in this zone. It was shown that the stand-alone high-resolution model (domain: southern Baltic Sea) obtained similar results to the same model system but nested in the mesoscale model (domain: Baltic Sea). In addition, this model showed shorter simulation computation time and represents an independent, less vulnerable to discontinuity in forecast generation (lack of assimilation of boundary and initial conditions from a lower resolution model). A noticeable improvement in the quality of forecasts was shown by the AROME wind-field-powered model, which, due to its high resolution of the computational grid and wind data, maps well the wave dynamics in areas with limited wave exposure (the Vistula Lagoon, the Puck Lagoon) or complex coastline (the Hel Split) and seabed (the shallows of the Pomeranian Gulf and the Słupsk Shoal. The coupled data from the ALARO and AROME models, processed internally at IMWM-NRI, provide continuity and independence from global models and indicate applicability in generating wave forecasts by other Baltic countries.

The Helsinki Convention – a legal obstacle for carbon storage in the Baltic Sea?

The Convention on the Protection of the Marine Environment of the Baltic Sea Area – also known as the Helsinki Convention – was originally signed in 1974 by all Baltic Sea coastal countries, seeking to address the increasing environmental challenges from industrialisation and other human activities and that were having a severe impact on the marine environment. It entered into force on 3 May 1980. The Convention includes the protection of the Baltic Sea from all sources of pollution from land, air and sea. The Helsinki Convention was updated in 1992 to take into account the geopolitical changes and emerging environmental challenges in the region and was extended to ten Contracting Parties, including the European Union. The updated Helsinki Convention of 1992 entered into force on 17 January 2000.According to the articles in the Helsinki Convention [1] dumping in the Baltic Sea is generally forbidden. Carbon storage can be seen as dumping when regarding it as “deliberate disposal at sea or into the seabed of wastes or other matter” (article 2.4 a (i)). If there is not an applicable exemption (article 2.4 b – not seen as dumping, or 11.4 – exception from prohibition due to that safety of human life is threatened, or 29 – prohibition not applicable due to the relation to other Conventions) carbon storage then is forbidden (article 11.1), and that prohibition shall be implemented in national law through its national authorities (article 4.2).There is though a common interest among several countries around the Baltic Sea to be able to store carbon in the Baltic Sea in the future, in order to reduce CO2 emissions and reach the common climate goals. For example, Sweden is right now, through its authority Geological Survey of Sweden, investigating the possibility of storing carbon within Swedish territory in the Baltic Sea.Therefore, there is also a discussion among the countries who have signed the Helsinki Convention about how to go forward making sure carbon storage is in agreement with the Convention. One way could be to look at how this problem was dealt with in the London Protocol – 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, 1972 (see article 4.1, and Annex I 1.8 and 4) [2], where carbon dioxide was added to the list of matter that may be considered for dumping if certain conditions are being met (disposal into a sub-seabed geological formation, consisting overwhelmingly of carbon dioxide, no wastes or other matter are added for the purpose of disposing of those wastes or other matter).

Bottom-trawling signals lost in sediment: A combined biogeochemical and modeling approach to early diagenesis in a perturbed coastal area of the southern Baltic Sea

Trawl-fishing is broadly considered to be one of the most destructive anthropogenic activities toward benthic ecosystems. In this study, we examine the effects of bottom-contact fishing by otter trawls on the geochemistry and macrofauna in sandy silt sediment in an area of the Baltic Sea where clear spatial patterns in trawling activity were previously identified by acoustic mapping. We calibrated an early diagenetic model to biogeochemical data from various coring locations. Fitting measured mercury profiles allowed for the determination of the sediment mixing and burial velocity. For all sites, independent of the trawl mark density, good fits were obtained by applying the model with the same organic matter loading and parameter values, while iron fluxes scaled linearly with the burial velocity. A sensitivity analysis revealed that the fitted sulfate reduction rate, solid sulfur contents, ammonium concentration, and both the isotopic composition and concentration of dissolved inorganic carbon provided reliable constraints for the total mineralization rate, which exhibited a narrow range of variability (around ±20 % from the mean) across the sites. Also, the trawling intensity did not significantly correlate with total organic carbon contents in surficial sediment, indicating limited loss of organic matter due to trawling. The fits to the reactive iron, acid volatile sulfur, chromium(II) reducible sulfur contents, and porewater composition demonstrate that sediment burial and mixing primarily determine the redox stratification. The mixing depth did not correlate with trawling intensity and is more likely the result of bioturbation, as the analyzed macrofaunal taxonomy and density showed a high potential for sediment reworking. The extraordinarily long-lived Arctica islandica bivalve dominated the infaunal biomass, despite the expectation that trawling leads to the succession from longer-lived to shorter-lived and bigger to smaller macrofauna. Our results further suggest that a clear geochemical footprint of bottom-trawling may not develop in sediments actively reworked by tenacious macrofauna.

First record of Pseudoterranova decipiens in sprat (Sprattus sprattus) from the Baltic Sea.

A dispersion of Anisakidae nematodes (particularly Contracaecum osculatum) among marine organisms in the Baltic Sea has been reported over the last decade. This is in line with an increase in the number of grey seal that act as final host for Contracaecum osculatum and Pseudoterranova sp., and are thus indispensable for the completion of their life cycles. Most attention has been paid to zoonotic nematode species, like Pseudoterranova sp., which have been noted in commercially important fish in the area. Little is known about the spread and transmission of Pseudoterranova sp. in the Baltic Sea. The aim of this study was to investigate whether sprat may play a role as a transport host for this Anisakidae. Samples were collected in three areas of the southern Baltic Sea (south and east of Bornholm, Słupsk Farrow and the Gulf of Gdańsk) during a research cruise in August 2019. A visual inspection of the viscera of 556 sprats was conducted. Parasites were identified using anatomomorphological and molecular methods. Nematodes were recorded only in sprat caught southeast of Bornholm (prevalence 2.7%; intensity of infection 1-4; abundance 0.05). Molecular identification revealed the presence of Pseudoterranova decipiens. This is the first report of P. decipiens in sprat from the Baltic Sea. Sprat is likely a transmitter of P. decipiens in the Baltic Sea food web.

Centralized Offshore Hydrogen Production from Wind Farms in the Baltic Sea Area—A Study Case for Poland

In Poland, hydrogen production should be carried out using renewable energy sources, particularly wind energy (as this is the most efficient zero-emission technology available). According to hydrogen demand in Poland and to ensure stability as well as security of energy supply and also the realization of energy policy for the EU, it is necessary to use offshore wind energy for direct hydrogen production. In this study, a centralized offshore hydrogen production system in the Baltic Sea area was presented. The goal of our research was to explore the possibility of producing hydrogen using offshore wind energy. After analyzing wind conditions and calculating the capacity of the proposed wind farm, a 600 MW offshore hydrogen platform was designed along with a pipeline to transport hydrogen to onshore storage facilities. Taking into account Poland’s Baltic Sea area wind conditions with capacity factor between 45 and 50% and having obtained results with highest monthly average output of 3508.85 t of hydrogen, it should be assumed that green hydrogen production will reach profitability most quickly with electricity from offshore wind farms.

Gas - Escape features along the Trzebiatów fault offshore Poland: Evidence for a leaking petroleum system

New 2D high-resolution seismic and hydro-acoustic data demonstrate the presence of methane in the shallow sediments and its origin in the Pomeranian Bight, south of the Baltic Sea area. Various shallow gas features including chimneys, bright spots, acoustic blanking, pockmarks, and polarity reversal were identified in the Gryfice block, along the inverted Trzebiatów fault zone. Structural and stratigraphic interpretation with support of seismic attributes shows the potential of fluid migration pathways from the Upper Triassic formation reservoirs to shallow sediments below the seafloor. It also helps in the explanation of how this natural gas escapes to the sea bottom. Amplitude-vs-offset (AVO) analysis proved free gas existence in the potential Upper Triassic reservoir, and helped locate free gas deposits within sediments. Hydro-acoustic data illustrated the gas chimneys’ anomalies and the corresponding free gas accumulation in Pleistocene to Quaternary successions. Leaking of gas to the seafloor was also proved by the exposure of pockmarks on multibeam (bathymetry) data at the seafloor. We combine seismic, hydro-acoustic data, and information on petroleum system from previous studies to explain the signatures of free gas and its migration from lower reservoirs to shallow sediments.

Four-Dimensional Variational Data Assimilation and Sensitivity of Ocean Model State Variables to Observation Errors

The use of Four-Dimensional variational (4D-Var) data assimilation technology in the context of sea dynamics problems, with a sensitivity analysis of model results to observation errors, is presented. The technology is applied to a numerical model of ocean circulation developed at the Marchuk Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), with the use of the splitting method and complemented by 4D-Var data assimilation with covariance matrices of background and observation errors. The variational data assimilation involves iterative procedures to solve inverse problems so as to correct sea surface heat fluxes for the model under consideration. An algorithm is formulated to study the sensitivity of the model outputs, considered as output functions after assimilation, to the observation errors. The algorithm reveals the regions where the output function gradient is the largest for the average sea surface temperature (SST) in a selected area, obtained by assimilation. In the numerical experiments, a 4D variational problem of SST assimilation for the Baltic Sea area is solved.

Temporal development of fish communities in brackish lagoons of the Baltic Sea considering the invasion of the non-indigenous round goby (Neogobius melanostomus)

Globally, successful invasions of non-indigenous species affect biodiversity and can push ecosystems beyond tipping points. This study aimed to identify factors that influence round goby (Neogobius melanostomus) abundances and distribution pathways along the eastern German coast of the Baltic Sea over a 12year period. The study further explored how the invasion of round goby affected the local fish and benthos assemblages in terms of species numbers and diversity. Round goby invaded various areas and estuaries and has established self-sustaining populations at low densities with further westward spread along the coast appearing to be ongoing. Salinity emerged as the most important predictor for overall round goby abundance, while the influence of macrozoobenthos abundance, vegetation cover, oxygen concentration, and water temperature were comparably low, indicating that round goby have a high tolerance in this regard. Negative impacts of round goby on benthic organisms and indigenous fish species, such as native gobiids, flounder (Platichthys flesus), ruffe (Gymnocephalus cernua), perch (Perca fluviatilis), pikeperch (Sander lucioperca), and cod (Gadus morhua), were not observed. This could be attributed to the comparably low densities of round goby at the sampling areas (0.0001 to 0.2 fish per m2) in combination with a potential surplus of benthic resources counteracting negative effects of predation and competition. The results suggest that its broad environmental adaptability could have enabled round goby to occupy a vacant ecological niche in coastal areas of the south-western Baltic Sea, which is generally considered to be species-poor due to strong environmental gradients. However, it cannot be excluded that certain effects of the round goby invasion may be too subtle to be detected. Thus, the results of our study underline the need for a specific long-term monitoring of the round goby invasion across taxa and habitats.