We address the impact of systematic changes in the wave directions to the magnitude and direction of wave-induced sediment transport along the southern and eastern sedimentary Baltic Sea shores. The analysis was performed using the CERC approach in terms of potential alongshore sediment transport based on SWAN-reconstructed wave time series forced by ERA5 winds for 1990–2021. The majority of transport is driven by waves approaching from one or two narrow (±15°) ranges of prevailing wave directions. These wave systems produce mostly >60% and in many locations up to 80–90% of the total transport. While either clockwise (CW) or counterclockwise (CCW) transport predominates in a part of the study area, many locations experience a delicate balance of transport under the impact of waves from the south-west and north-west and adjacent directions that generate CW and CCW transport. We show that the prevailing wave directions that drive most of the transport have not changed 1990–2021. Instead, the balance of waves from these directions has changed because of a systematic decrease in the frequency of waves from the north-west and adjacent directions. The overall intensity of transport driven by waves from these directions has considerably decreased in about 1/3 of the study area. The decrease rate of CW transport is up to 16,000 m 3 /yr. Such alterations infringe the balance or even direction of sediment transport in sectors affected by bi-directional wave patterns but usually only affect the magnitude of sediment transport in coastal sectors that develop under the impact of a single-peak wave system. • Prevailing wave directions driving most of sediment transport are identified. • Waves from SW and NW keep fragile balance of transport on the Baltic proper shores. • Significant changes have occurred in sediment transport across the study area. • The reason is a decrease in the frequency of waves from the north-west. • Changes in wave fields have varying impact across the study area.

Accumulation of phenol derivatives and microplastic in ferromanganese nodules (Fe-Mn) from Polish Exclusive Economic Zone - preliminary studies.

The spread of aquatic non-indigenous species (NIS) is recognised as a major threat to the recipient regions ecosystems. The present study reviewed all NIS that have been introduced to the marine waters of the European Union (EU) until 2021, and their introduction pathways. Further, the study statistically analysed temporal trends in new NIS introductions and addressed uncertainties in relation to transporting pathways. Time-series analyses indicated that the observed trends in new NIS introductions have followed smoothly increasing trajectories for the entire study area, Mediterranean Sea, North-East Atlantic Ocean, and the Baltic Sea, whereas abrupt increase was detected for the Black Sea. It is noteworthy that the increasing trends started to slow down at the end of 2010s. Strongly increased research interest towards marine invasions since the early 2000s, and new environmental policies likely affected the observed trends. Future updates will be key to assessing whether this slowdown is truly a persisting trend or only an anomaly in the long term. The pathway assessment suffered from notable uncertainties, as the assigned confidence levels for pathways were low or unassigned for a large proportion of the introduced NIS in all study regions. Transport by shipping vectors was assigned as the most common pathway (51%) for new NIS introductions to EU seas, although there was very rarely direct evidence of this. The study highlights the need to overcome the pathway uncertainties, as robust information on introduction pathways is critical to manage new NIS introductions effectively.

Understanding future shoreline evolution is fundamental to developing adaptive coastal management strategies under climate change scenarios. This study analyzes the Southern Baltic Sea’s ∼37-km stretch comprising Usedom and Wolin islands, where sandy coastlines face intensifying erosion threats under rising anthropogenic and climatic pressures. We introduce an explainable Long Short-Term Memory Recurrent Neural Network (LSTM-RNN) framework designed to bridge the gap between Deep Learning (DL) performance and physical interpretability in decadal forecasting. The results show that the best model achieves a Root Mean Squared Error (RMSE) of 10.40 m, Mean Absolute Error (MAE) of 7.13 m, and R-squared (R 2 ) of 0.55. Deep SHapley Additive exPlanation (DeepSHAP) attribution reveals that erosion is driven by the compound interaction of sea-level rise (SLR), storm surges, and extreme waves. This transferable framework represents a significant methodological contribution, enhancing regional early-warning systems and providing a robust, "white-box" approach for Baltic Sea’s operational coastal management. • A sequence-aware neural network model forecasts decadal shoreline change until 2050. • The best model achieves an R-squared value of 0.55 for decadal shoreline change. • Explainable models show erosion is driven by sea levels and extreme waves. • Widespread erosion intensification is projected for the Southern Baltic by 2050.

The major goal of this study was to identify long term (1998–2022) changes within the macrobenthic communities in the Sound (Öresund), with special emphasis on climate change. Bottom trawling in this area has been banned since 1932. This was compared to changes of the same species at the surrounding Swedish west coast in the north (the Kattegat and the Skagerrak) and the Baltic Sea in the south. Results are also related far back in time in the Sound as the benthic fauna has been unusually well-studied since the 1800s. It is of special interest to study the faunal response to the rise in bottom water temperature which has been recorded in later years. The Sound between Denmark and Sweden is situated between the Baltic Sea, one of the largest brackish waters, and the Kattegat, an extension of the Atlantic. This location provides special conditions for a benthic fauna with a northern touch. Brackish water species typical of the Baltic occur here, but also marine cold-water species typical of the Arctic. Many species therefore live on their edge of distribution in the Sound. The development in abundance 1998–2022 in the Sound with its trawl-ban was similar to heavily trawled areas along the Swedish west coast. Species with a northern distribution were found to decrease parallel with an increase in species with a southern distribution. The sharper reduction in abundance in the Sound compared to surrounding seas may be due to the fact that many species here live at the extreme edge of their range. Indications of disturbed reproduction and submergence in some northern species were also recorded. The most likely explanation of these changes is the increase in temperature which affects many processes that may act in synergy. The transition from a Haploops community to an Amphiura community probably started with hypoxia and high temperatures. Also, temperature and decreasing levels of nitrogen, which control primary production, may have created relative food shortages as Haploops especially seems to benefit from a high trophic level. The change in faunal composition implied a reduction in gamma diversity but also a loss in nutritional value for commercial fish. Increased temperature is likely an explanation why northern species with non-pelagic larvae have decreased and why southern species with pelagic larvae have increased in recent years. This study, where comparisons are difficult because of many complicating factors, verifies that broken time series is an urgent problem for long-term ecological and environmental studies. It is important for the future to preserve long-term series of data collected at the same location and with the same methods.

Breeding phenological responses to changing environments affect demographics and population persistence. However, inter-individual variation in adjustment of reproductive timing to predation risk has been overlooked. We thus tested whether increasing natural predation risk enhanced or homogenized reproductive timing of females differing in risk sensitivity. Using behavioral (flight initiation distance, FID) and cognitive (relative head volume) proxies of risk sensitivity, we analyzed laying dates of female common eiders (Somateria mollissima) breeding in SW Finland (Baltic Sea) relative to conspecifics under fluctuating predation pressure, while accounting for breeding experience and body condition. We found that high predation risk was associated with a divergence of female eider breeding phenologies depending on cognitive but not behavioral proxies of risk sensitivity. Accordingly, relatively large-headed females, assumed to be more risk-sensitive, bred later than small-headed ones following years of high adult or nest predation risk-plausibly reflecting extended nest prospecting in risk-sensitive individuals-leading to greater laying asynchrony. In contrast, females displaying longer FIDs (more risk-sensitive) bred earlier than those displaying shorter FIDs, but this response was irrespective of the level of predation risk. Because FID was measured late in incubation, we hypothesize that it may more strongly reflect state-dependent parental investment in the current breeding attempt than risk sensitivity during nest initiation, with higher parental investment promoting delayed escape. Additionally, experienced breeders bred earlier than inexperienced ones. More attention should be given to cognitive traits and behaviors associated with risk sensitivity to better understand variation in individual breeding phenology and synchrony.

Abstract Cryptic introductions often remain unnoticed, but can have unforeseen consequences for the invaded ecosystems. A sudden eastward range expansion of the Rockpool shrimp Palaemon elegans into the low-salinity part of the Baltic Sea in the 2000s could genetically be identified as a cryptic introduction of a distinct Black Sea lineage. To understand the risk of its expansion westwards into the North Sea and Atlantic and competitive displacement of the native Atlantic lineage, we surveyed the distribution of both mitochondrial lineages at different salinities along the Baltic and North Sea, investigated the temporal stability of this pattern over 15 years and the pre-introduction distribution of the native Atlantic lineage in the Baltic Sea. Salinity correlated significantly with the frequency of the lineages, while the time series did not indicate an increase in relative abundance over time and the historical distribution of the assumed Atlantic lineage aligns with its current distribution. We conclude that the non-native Black Sea lineage is unlikely to expand further into the Atlantic, and has not replaced the Atlantic lineage.

Dreissena polymorpha, the zebra mussel, is one of the most widespread and ecologically disruptive invasive species in European freshwater systems. Despite its long presence in Latvia, genetic information on local populations has been lacking. This study provides the first comprehensive assessment of genetic diversity and population structure of D. polymorpha across seven Latvian waterbodies, representing lakes, a reservoir, and a river system. Individuals were genotyped using five polymorphic microsatellite loci. Genetic variation was analysed through the standard genetic parameters, namely, number of alleles and frequency, heterozygosity estimates and genetic differentiation was estimated using FST statistics, Bayesian clustering, PCA, and Nei’s genetic distance. All loci were polymorphic, and no evidence of null alleles or recent bottlenecks was detected. Populations exhibited high genetic diversity. Significant heterozygote deficits were found in most populations. Genetic differentiation among populations was moderate overall, though three geographically proximate lakes showed minimal differentiation. Bayesian clustering and PCA identified four distinct genetic groups, indicating that hydrological isolation and limited dispersal contribute to population structuring. These findings demonstrate that Latvian D. polymorpha populations maintain substantial genetic diversity and exhibit clear spatial genetic structuring. This genetic information provides an essential foundation for monitoring invasion dynamics and informing management strategies aimed at limiting further spread and ecological impact.

Modern agriculture is increasingly reliant on imported fertilizers and subject to price volatility, compounded by environmental pressures arising from the overuse of synthetic fertilizers. This study assessed the impact of Furcellaria lumbricalis algal biostimulant, produced by anaerobic fermentation, on dry matter yield and plant development indicators of garden radish (Raphanus raphanistrum subsp. sativus) in five soil substrate types. Biostimulant doses aimed at reducing mineral fertilizer application to 75% of the full rate while maintaining or improving yield were evaluated; yet no statistically significant effect on dry matter yield was observed, and the hypothesis was therefore not statistically confirmed. The experiment included five substrate types (sandy clay, sandy clay with organic matter, sand, sand with organic matter, and peat) and six fertilizer/biostimulant treatments, including 75% mineral fertilizer combined with 3%, 6%, and 12% algal biostimulant concentrations. Linear mixed models showed that substrate type (F = 19.58; p < 0.001) and fertilizer variant (F = 5.00; p < 0.001) had statistically significant effects on total dry matter yield, but their interaction was not statistically significant. All 75% and 100% mineral fertilizer variants with and without biostimulant produced statistically significantly higher yields than the unfertilized control (p = 0.0016–0.0337). The leaf development indicator (AtLeaf) index was statistically significantly higher in all biostimulant variants compared to the unfertilized control. Principal component analysis (PCA) and redundancy analysis (RDA) demonstrated that substrate type determines the primary structure of the substrate–plant system, while biostimulant effects were expressed as modulation of existing processes within the substrates. The results indicate substrate-specific responses to Baltic Sea algal Furcellaria lumbricalis digestate with statistically significant effect observed only in peat, consistent with previous findings, while no significant effects were detected in other substrates. Although the effects of the biostimulant on dry matter yield were not consistently statistically significant, the observed trends in plant development indicators and substrate–plant system responses suggest that Furcellaria lumbricalis digestate may have potential as a nutrient recycling component within a circular bioeconomy framework.

There is no denying either the importance of the Baltic Sea or the strategic importance of the Kola Peninsula to Russia’s military deterrent. It is in Russia’s interest to secure the use of these areas for all eventualities. The country’s armed forces are expected to increase in size in the coming years, and this will result in both changes to the force structure and the establishment of new forces, especially on the borders of north-west Russia. Alongside this, the inevitable thawing of the Northeast Passage will bring new challenges and actors to the region, impacting the general security situation there. In the current situation, where transatlantic relations are in a state of flux, it is important that the EU and NATO’s European member states also prepare for China to become more aggressive in terms of its military capabilities in the northern regions.

Abstract Marine nematodes of the genus Anisakis are shaped by complex life cycles and heterogeneous marine environments, yet the molecular basis of their developmental and population differentiation remains poorly understood. Here, we analyzed mRNA and long non-coding RNA expression in third- and fourth-stage larvae of Anisakis simplex (s. s.) collected from the Baltic Sea and the Northeast Atlantic using high-throughput RNA sequencing. Larval development was associated with extensive transcriptional remodeling involving cuticle organization, metabolism, proteolysis, and host-interaction pathways. Comparisons between populations revealed pronounced geographic divergence, including population-specific gene expression and reversal patterns shared across developmental stages. A subset of long non-coding RNAs was linked to the regulation of developmentally and population-biased genes, targeting pathways related to energy metabolism, ion transport, and protein synthesis. These findings demonstrate that developmental progression and geographic origin jointly shape the transcriptomic architecture of Anisakis simplex (s. s.), providing insight into molecular mechanisms underlying parasite adaptation with potential relevance for ecology, evolution, and anisakiasis risk.

ABSTRACT This study quantifies operational variability across major ship types and size classes in the North and Baltic Seas using one year of AIS data. A framework of twelve operational metrics is developed to capture key dimensions of ship operations and aggregated into variability scores at ship-type and size-class level. Results reveal clear structural differences: cargo segments such as container, vehicle, and bulk carriers exhibit low variability and highly standardized operations, while passenger and service vessels show pronounced heterogeneity. Variability generally decreases with vessel size, indicating increasing operational standardization. Decomposition analysis identifies engine performance and energy use as primary drivers of variability, followed by routing and loading, while speed plays a minor role. Sensitivity analyses confirm robustness across weighting schemes. The findings provide empirically grounded reference values for improving fleet-level emission and compliance models and support more realistic assessments of maritime decarbonization strategies.

The spatiotemporal dynamics of marine microplastics remain obscure and pose significant challenges for global marine protection. To address this knowledge gap, we compiled a global data set of marine surface microplastic observations (0-5 m, 1998-2023) and employed data-driven models coupled with statistical methods to quantify the spatiotemporal dynamics and driving mechanisms of marine microplastics. The total quantity of marine surface microplastics (primarily 0.33-5 mm) is approximately 3.29 × 1014 items, which represents an update to previous estimates. Microplastic concentrations significantly increased in 72.59% of global marine areas, with an annual growth rate of 4.53%. Ocean dynamics under thermohaline regulation facilitates microplastic transport and seasonal accumulation, a process that may be intensified by climate warming. Total microplastic loads in the Northern Hemisphere are 18.31% (95% confidence interval: 13.75%-27.57%) greater during summer than in winter, highlighting seasonal exposure variations for marine ecosystems. Notably, targeted policy interventions resulted in an 82.54% reduction in potential loading in the Baltic Sea. The unique spatiotemporal dynamics of marine microplastics revealed in this study provide key insights for microplastic risk assessment and control.

Climate change affects all organisms, including mosquitoes. Shorter, milder winters and prolonged vegetation period are expected to increase mosquito populations, thereby heightening the risk of mosquito-borne disease transmission. West Nile fever exemplifies a disease that has expanded northward in recent decades, now endemic in Germany as far as the Baltic Sea coast. Additionally, mosquito species are shifting their geographical distribution. For instance, Culex modestus, known for transmitting West Nile virus, was first identified in Sweden in 2016. Invasive species like Aedes albopictus are also expanding with concurrently autochthonous transmissions of Dengue fever to humans in Europe. In 2023, two Aedes albopictus introductions were recorded in Sweden, likely occur-ring regularly, though no established populations have been confirmed. Malaria, once widespread in Sweden during the 18th and 19th centuries, disappeared, yet reintroduction due to climate change seems highly unlikely. Swedish health care must be prepared to diagnose Dengue and Chikungunya in travelers to southern Europe as well as for the emergence of West Nile virus in southernmost Sweden.

Abstract Warming temperatures, heat waves, and altered conditions associated with climate change affect biodiversity and ecological processes across environments, with coastal zones being particularly vulnerable. Biofilm-forming organisms in shallow coastal areas are taxonomically diverse and include bacteria, fungi, and algae that contribute to energy and nutrient cycling along with providing habitats and food for species at the base of the food web. To understand how biofilm-forming organisms respond differently to spatiotemporally changing environmental conditions, seasonal sampling was performed in a Baltic Sea bay that has undergone 50 years of thermal heating, an unaffected nearby control bay, and a temperature gradient along an exposed coastline between the bays. The diversity, composition, and seasonal dynamics of the biofilm communities differed between the three environments largely due to temperature and water chemistry, with biofilms in the heated bay being more similar across seasons compared with the control bay and the gradient, and with prokaryotes exhibiting stronger spatial heterogeneity and seasonal dynamics compared to micro-eukaryotes. In the gradient, the dominating taxonomic groups were distinct, community composition was primarily influenced by seasonal turnover and wave exposure, and alpha diversity of prokaryotes decreased with increasing temperature. Seasonal shifts in the composition of micro-eukaryotic heterotrophs, phototrophs, and mixotrophs differed between environments, with heterotrophs being more dominant at higher temperatures. In conclusion, these contrasting responses indicated that climate warming may disproportionately impact different components of coastal biofilm communities, potentially decoupling key ecological processes and reducing community resilience in Baltic Sea coastal habitats.

ABSTRACT Climate factors shape the spring phenology of migrant birds in Europe. We examined carry-over effects of temperature and rainfall in four regions of Europe on the spring migration timing of a medium-distance migrant, Eurasian Wren, at the southern Baltic coast over 60 years. We modelled the effects of these climate factors on the timing of the start (10%), median (50%) and end (90%) of wrens’ spring passage at the bird ringing station Hel (N Poland) during 1964–2023. The dates of start and median of spring passage have not changed, but the end shifted earlier by 5.7 days over these 60 years. The start, median and end dates of wren passage on the Baltic coast were early after warm autumn, winter or spring, but delayed after high autumn and winter rainfall in central and northern Europe. Analogous climate conditions in southern and south-western Europe had the opposite effect on wrens’ timing of passage. High spring rainfall in central and southern Europe delayed spring passage at Hel. High rainfall in early summer in northern Europe was related to early wren passage the following spring, but such conditions in late summer resulted in a delay of spring passage. We assume that temperature and rainfall in these regions influence the timing of wren spring passage through their effect on food availability, individual fitness, migration distance and proportion of immatures among migrants. We suggest that varied humidity, which caused different insect abundance for wrens, explains the varied effects of rainfall in various regions of Europe on the timing of wren spring passage at Hel. We show that wrens’ spring migration phenology in the Baltic region is shaped by a combination of carry-over effects of many environmental factors. They affect wrens in regions of Europe where they stay previously, even months before their spring migration.

Very little is known about the origins and history of domestic chickens (Gallus gallus domesticus) in northern Europe due to a lack of existing documentary and ancient DNA evidence from this region. Therefore, we conducted ancient DNA analyses and radiocarbon dating of archaeological chicken bones from the Baltic Sea region (Finland, Estonia, and Lithuania). We sequenced a 201-bp long fragment of the mitochondrial control region as well as SNPs (single nucleotide polymorphisms) from the thyroid-stimulating hormone receptor (TSHR) gene and the β-carotene dioxygenase 2 (BCDO2) gene, comparing with modern Finnish and Estonian landrace chickens, as well as with other ancient and modern chickens. All studied ancient chickens belonged to a prevalent E1 mitochondrial haplogroup, except one individual from the Åland Islands (haplogroup B). Allele frequencies differed between ancient Baltic and Finnish chickens from Åland Islands in TSHR and BCDO2 genes, with Åland harbouring more individuals with grey skin. Interestingly, yellow-skinned chickens were more common in mainland Finland and Baltic countries during ancient times than in central and southern Europe. Mitochondrial haplogroup A was present in modern Finnish landrace chickens but not in ancient samples from the early Finnish Iron Age to the early modern period (3rd-18th century CE), indicating later introgression. Both Estonian and Finnish landrace chickens had a higher frequency of the TSHR wild-type allele than the modern reference samples. Based on our results, the ancient chickens from the Åland Islands differed from other ancient chickens from the Baltic Sea region, and the landrace chickens differ from other modern chickens.

ABSTRACT Microalgae from ice and under-ice water communities can serve as valuable models for studying how unique physiological adaptations influence the phylogeography of single-celled eukaryotes. Gymnodinium baicalense is a freshwater planktonic dinoflagellate, historically recognized as one of the few freshwater dinoflagellates with a restricted distribution, primarily within the Lake Baikal region. However, we found a similar morphospecies far from this area – in Lake Ilmen – which differs from Lake Baikal in numerous characteristics including age, depth, trophic status, oxygen saturation, transparency, and chemical stability. Genetic analyses, combined with morphological and ecological data revealed the close evolutionary relationships between these freshwater lineages and Gymnodinium corollarium from the Baltic Sea. We propose that the Lake Baikal and Lake Ilmen lineages belong to the same species, though the Baikal lineage due to its remote location has accumulated some unique mutations in its rDNA. A single episode of marine–freshwater transition, with further G. baicalense colonization of various lakes is suggested as the most likely scenario of the species dispersal. This discovery challenges the notion of G. baicalense as an endemic species and prompts to check of under-ice dinoflagellate blooms in other northern freshwater lakes.

Undersea communication cables have become strategic infrastructure because they sit at the intersection of economic connectivity, military resilience, and information stability. Generally, privately financed and operated, and routinely damaged by accidents, they carry almost all international data traffic and are increasingly probed through ambiguous, below-threshold disruption. The papertherefore provides a forward-looking assessment of risks and governance gaps in cable security. It argues that cable security is best understood as a problem of resilience governance under uncertainty. It also argues that network signalling under uncertainty can reduce leverage created by ambiguous incidents when attribution remains probabilistic. It develops a framework in which governments, operators, local authorities, regulators, Northern and Indigenous governments, and communities signal collectively through operations, law, repair readiness, and public communication. Empirically, the paper treats Canada’s Arctic and North Pacific approaches as the core case and the Baltic Sea and adjacent North Sea as a learning environment. It uses Baltic incidents and NATO–EU responses to identify building block practices and to specify what a credible Canadian signalling posture could require. This includes cooperation with Japan and the Republic of Korea to extend this logic into the wider North Pacific.

Changes in sediment characteristics after a sand nourishment at the German Baltic Sea coast