A submerged Stone Age hunting architecture from the Western Baltic Sea.

The Baltic Sea basins, some of which only submerged in the mid-Holocene, preserve Stone Age structures that did not survive on land. Yet, the discovery of these features is challenging and requires cross-disciplinary approaches between archeology and marine geosciences. Here, we combine shipborne and autonomousunderwater vehicle hydroacoustic data with up to a centimeter range resolution, sedimentological samples, and optical images to explore a Stone Age megastructure located in 21 m water depth in the Bay of Mecklenburg, Germany. The structure is made of 1,673 individual stones which are usually less than 1 m in height, placed side by side over a distance of 971 m in a way that argues against a natural origin by glacial transport or ice push ridges. Running adjacent to the sunken shoreline of a paleolake (or bog), whose youngest phase was dated to 9,143 ±36 ka B.P., the stonewall was likely used for hunting the Eurasian reindeer (Rangifer tarandus) during the Younger Dryas or early Pre-Boreal. It was built by hunter-gatherer groups that roamed the region after the retreat of the Weichselian Ice Sheet. Comparable Stone Age megastructures have become known worldwide in recent times but are almost unknown in Europe. The site represents one of the oldest documented man-made hunting structures on Earth, and ranges among the largest known Stone Age structure in Europe. It will become important for understanding subsistence strategies, mobility patterns, and inspire discussions concerning the territorial development in the Western Baltic Sea region.

Estimation of functional diversity and species traits from ecological monitoring data.

The twin crises of climate change and biodiversity loss define a strong need for functional diversity monitoring. While the availability of high-quality ecological monitoring data is increasing, the quantification of functional diversity so far requires the identification of species traits, for which data are harder to obtain. However, the traits that are relevant for the ecological function of a species also shape its performance in the environment and hence, should be reflected indirectly in its spatiotemporal distribution. Thus, it may be possible to reconstruct these traits from a sufficiently extensive monitoring dataset. Here, we use diffusion maps, a deterministic and de facto parameter-free analysis method, to reconstruct a proxy representation of the species' traits directly from monitoring data and use it to estimate functional diversity. We demonstrate this approach with both simulated data and real-world phytoplankton monitoring data from the Baltic Sea. We anticipate that wider application of this approach to existing data could greatly advance the analysis of changes in functional biodiversity.

Population dynamics of Baltic herring since the Viking Age revealed by ancient DNA and genomics.

The world's oceans are currently facing major stressors in the form of overexploitation and anthropogenic climate change. The Baltic Sea was home to the first "industrial" fishery ∼800 y ago targeting the Baltic herring, a species that is still economically and culturally important today. Yet, the early origins of marine industries and the long-term ecological consequences of historical and contemporary fisheries remain debated. Here, we study long-term population dynamics of Baltic herring to evaluate the past impacts of humans on the marine environment. We combine modern whole-genome data with ancient DNA (aDNA) to identify the earliest-known long-distance herring trade in the region, illustrating that extensive fish trade began during the Viking Age. We further resolve population structure within the Baltic and observe demographic independence for four local herring stocks over at least 200 generations. It has been suggested that overfishing at Øresund in the 16th century resulted in a demographic shift from autumn-spawning to spring-spawning herring dominance in the Baltic. We show that while the Øresund fishery had a negative impact on the western Baltic herring stock, the demographic shift to spring-spawning dominance did not occur until the 20th century. Instead, demographic reconstructions reveal population trajectories consistent with expected impacts of environmental change and historical reports on shifting fishing targets over time. This study illustrates the joint impact of climate change and human exploitation on marine species as well as the role historical ecology can play in conservation and management policies.

120-years of ecological monitoring data shows that the risk of overhunting is increased by environmental degradation for an isolated marine mammal population: The Baltic grey seal.

The Baltic Sea is home to a genetically isolated and morphologically distinct grey seal population. This population has been the subject of 120-years of careful documentation, from detailed records of bounty statistics to annual monitoring of health and abundance. It has also been exposed to a range of well-documented stressors, including hunting, pollution and climate change. To investigate the vulnerability of marine mammal populations to multiple stressors, data series relating to the Baltic grey seal population size, hunt and health were compiled, vital demographic rates were estimated, and a detailed population model was constructed. The Baltic grey seal population fell from approximately 90,000 to as few as 3000 individuals during the 1900s as the result of hunting and pollution. Subsequently, the population has recovered to approximately 55,000 individuals. Fertility levels for mature females have increased from 9% in the 1970s to 86% at present. The recovery of the population has led to demands for increased hunting, resulting in a sudden increase in annual quotas from a few hundred to 3550 in 2020. Simultaneously, environmental changes, such as warmer winters and reduced prey availability due to overfishing, are likely impacting fecundity and health. Future population development is projected for a range of hunting and environmental stress scenarios, illustrating how hunting, in combination with environmental degradation, can lead to population collapse. The current combined hunting quotas of all Baltic Nations caused a 10% population decline within three generations in 100% of simulations. To enable continued recovery of the population, combined annual quotas of less than 1900 are needed, although this quota should be re-evaluated annually as monitoring of population size and seal health continues. Sustainable management of long-lived slowly growing species requires an understanding of the drivers of population growth and the repercussions of management decisions over many decades. The case of the Baltic grey seal illustrates how long-term ecological time series are pivotal in establishing historical baselines in population abundance and demography to inform sustainable management.

Impact of health spending on hospitalization rates in Baltic countries: a comparative analysis.

INTRODUCTION: This study examines the association between healthcare indicators and hospitalization rates in three high-income European countries, namely Estonia, Latvia, and Lithuania, from 2015 to 2020. METHOD: We used a sex-stratified generalized additive model (GAM) to investigate the impact of select healthcare indicators on hospitalization rates, adjusted by general economic status-i.e., gross domestic product (GDP) per capita. RESULTS: Our findings indicate a consistent decline in hospitalization rates over time for all three countries. The proportion of health expenditure spent on hospitals, the number of physicians and nurses, and hospital beds were not statistically significantly associated with hospitalization rates. However, changes in the number of employed medical doctors per 10,000 population were statistically significantly associated with changes of hospitalization rates in the same direction, with the effect being stronger for males. Additionally, higher GDP per capita was associated with increased hospitalization rates for both males and females in all three countries and in all models. CONCLUSIONS: The relationship between healthcare spending and declining hospitalization rates was not statistically significant, suggesting that the healthcare systems may be shifting towards primary care, outpatient care, and on prevention efforts.

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, Slupsk Farrow and the Gulf of Gdansk) 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.

Diversity of Sarcocystis parasites in southeastern Baltic Sea catchment ecosystems.

Currently, research on apicomplexan Sarcocystis parasites is mainly carried out by analyzing animal carcasses. However, environmental studies would not only allow faster detection of possible sources of infection but also avoid the use of animals for investigations. Therefore, in the current study, we aimed to identify tested Sarcocystis species in sediment collected from water bodies located in the southeastern Baltic countries. A total of 99 sediment samples were collected during the summer from different types of water bodies in Estonia, Latvia, Lithuania, and Poland. Species-specific nested PCR targeting cox1 gene was used for the detection of selected Sarcocystis species (S. cruzi, S. bovifelis, S. hirsuta, S. arieticanis, S. tenella, S. capracanis, S. miescheriana, and S. bertrami) infecting livestock. The results showed a statistically lower (p < 0.05) occurrence of Sarcocystis parasites in Estonia (50%) compared to three countries, where the detection rate of Sarcocystis spp. DNA was remarkably higher, ranging from 88 to 100%. Among Sarcocystis species tested, S. cruzi (83.8%) and S. arieticanis (55.6%) using cattle and sheep as their intermediate hosts were most commonly identified. The detection rates of some of the analyzed Sarcocystis species were significantly different in southeastern Baltic countries. It is discussed that the detection rates of certain Sarcocystis species depend not only on the number of animals per 1 km2 but also on various ecological factors and farming practices that differ in the amount of contact domestic animals have with predators and the potential for animals to become infected through natural water or food sources.

A metabarcoding analysis of the wrackbed microbiome indicates a phylogeographic break along the North Sea-Baltic Sea transition zone.

Sandy beaches are biogeochemical hotspots that bridge marine and terrestrial ecosystems via the transfer of organic matter, such as seaweed (termed wrack). A keystone of this unique ecosystem is the microbial community, which helps to degrade wrack and re-mineralize nutrients. However, little is known about this community. Here, we characterize the wrackbed microbiome as well as the microbiome of a primary consumer, the seaweed fly Coelopa frigida, and examine how they change along one of the most studied ecological gradients in the world, the transition from the marine North Sea to the brackish Baltic Sea. We found that polysaccharide degraders dominated both microbiomes, but there were still consistent differences between wrackbed and fly samples. Furthermore, we observed a shift in both microbial communities and functionality between the North and Baltic Sea driven by changes in the frequency of different groups of known polysaccharide degraders. We hypothesize that microbes were selected for their abilities to degrade different polysaccharides corresponding to a shift in polysaccharide content in the different seaweed communities. Our results reveal the complexities of both the wrackbed microbial community, with different groups specialized to different roles, and the cascading trophic consequences of shifts in the near shore algal community.

Salinity and host drive Ulva-associated bacterial communities across the Atlantic-Baltic Sea gradient.

The green seaweed Ulva is a model system to study seaweed-bacteria interactions, but the impact of environmental drivers on the dynamics of these interactions is little understood. In this study, we investigated the stability and variability of the seaweed-associated bacteria across the Atlantic-Baltic Sea salinity gradient. We characterized the bacterial communities of 15 Ulva sensu lato species along 2,000 km of coastline in a total of 481 samples. Our results demonstrate that the Ulva-associated bacterial composition was strongly structured by both salinity and host species (together explaining between 34% and 91% of the variation in the abundance of the different bacterial genera). The largest shift in the bacterial consortia coincided with the horohalinicum (5-8 PSU, known as the transition zone from freshwater to marine conditions). Low-salinity communities especially contained high relative abundances of Luteolibacter, Cyanobium, Pirellula, Lacihabitans and an uncultured Spirosomaceae, whereas high-salinity communities were predominantly enriched in Litorimonas, Leucothrix, Sulfurovum, Algibacter and Dokdonia. We identified a small taxonomic core community (consisting of Paracoccus, Sulfitobacter and an uncultured Rhodobacteraceae), which together contributed to 14% of the reads per sample, on average. Additional core taxa followed a gradient model, as more core taxa were shared between neighbouring salinity ranges than between ranges at opposite ends of the Atlantic-Baltic Sea gradient. Our results contradict earlier statements that Ulva-associated bacterial communities are taxonomically highly variable across individuals and largely stochastically defined. Characteristic bacterial communities associated with distinct salinity regions may therefore facilitate the host's adaptation across the environmental gradient.

Plutonium Signatures in a Dated Sediment Core as a Tool to Reveal Nuclear Sources in the Baltic Sea.

Plutonium distribution was studied in an undisturbed sediment core sampled from the Tvären bay in the vicinity of the Studsvik nuclear facility in Sweden. The complete analysis, including minor isotopes, of the Pu isotope composition (238Pu, 239Pu, 240Pu, 241Pu, 242Pu, and 244Pu) allowed us to establish the Pu origin in this area of the Baltic Sea and to reconstruct the Studsvik aquatic release history. The results show highly enriched 239Pu, probably originating from the Swedish nuclear program in the 1960s and 1970s and the handling of high burn-up nuclear fuel in the later years. In addition, the 244Pu/239Pu atomic ratio for the global fallout period between 1958 and 1965 is suggested to be (7.94 ± 0.31)·10-5. In the bottom layer of the sediment, dated 1953-1957, we detected a higher average 244Pu/239Pu ratio of (1.51 ± 0.11)·10-4, indicating the possible impact of the first US thermonuclear tests (1952-1958).

An overview of cervical cancer epidemiology and prevention in the Baltic States.

AIMS: To inform future Baltic States-specific policy analyses, we aimed to provide an overview of cervical cancer epidemiology and existing prevention efforts in Estonia, Latvia and Lithuania. METHODS: A structured desk review: we compiled and summarized data on current prevention strategies, population demography and epidemiology (high risk human papillomavirus (HPV) prevalence and cervical cancer incidence and mortality over time) for each Baltic State by reviewing published literature and official guidelines, performing registry-based analyses using secondary data and having discussions with experts in each country. RESULTS: We observed important similarities in the three Baltic States: high burden of the disease (high incidence and mortality of cervical cancer, changes in TNM (Classification of Malignant Tumors) stage distribution towards later stage at diagnosis), high burden of high-risk HPV in general population and suboptimal implementation of the preventive strategies as low screening and HPV vaccination coverage. CONCLUSIONS: Cervical cancer remains a substantial health problem in the region and the efforts in addressing barriers by implementing a four-step plan for elimination cervical cancer in Europe should be made. This goal is achievable through evidence-based steps in four key areas: vaccination, screening, treatment, and public awareness.

Horizontal transmission of disseminated neoplasia in the widespread clam Macoma balthica from the Southern Baltic Sea.

Disseminated neoplasia (DN) is one of the most challenging and unrecognised diseases occurring in aquatic fauna. It has been diagnosed in four bivalve species from the Gulf of Gdansk (Southern Baltic Sea) with the highest frequency in Macoma balthica (formerly Limecola balthica), reaching up to 94% in some populations. The aetiology of DN in the Baltic Sea has not yet been identified, with earlier studies trying to link its occurrence with environmental pollution. Taking into account recent research providing evidence that DN is horizontally transmitted as clonal cells between individuals in some bivalve species, we aimed to test whether DN is a bivalve transmissible neoplasia (BTN) in the population of M. balthica from the Gulf of Gdansk highly affected with cancer. We examined mitochondrial cytochrome c oxidase I (mtCOI) and elongation factor 1α (EF1α) sequences of genomes obtained from haemolymph and tissues of neoplastic and healthy individuals. Sequence analysis resulted in detection of an independent transmissible cancer lineage occurring in four neoplastic clams that is not present in healthy animals. This study describes the first case of BTN in the clam M. balthica (MbaBTN), providing further insights for studies on this disease.

The burden of mental health-related mortality in the Baltic States in 2007-2018.

BACKGROUND: The problem of underestimating the burden of mental health-related mortality is widely discussed in the public health literature. Relevant scientific evidence from societies experiencing the largest burden of mental health mortality is important for better understanding global and national mental health challenges and improving policies. Three Baltic States - Estonia, Lithuania, and Latvia - are countries in the Central and Eastern European region that experienced post-soviet transition trauma and showed among the highest suicide and alcohol-related mortality rates in Europe. This study aimed to examine the change in the burden of mental health-related mortality in three Baltic States in the context of consistent growth in life expectancy in 2007-2018. METHODS: We calculated age-standardized years of life lost due to specific mental health-related causes of death in three Baltic countries from 2007 to 2018. Four mental health-related causes of death groups were analyzed: (i) all mental and behavioural disorders; (ii) intentional self-harm; (iii) main substance use-related causes of death; and (iv) external causes of death. The number of deaths came from the WHO Mortality Database; population exposures were extracted from the Human Mortality Database. RESULTS: We found that the proportion of age-standardized years of life lost due to mental disorders was relatively low in all three countries. It varied from 0.2% for females in Lithuania in 2009 to 2.4% for males in Estonia in 2007. However, the proportion of age-standardized years of life lost from self-harm and substance use remained high. In 2018, the proportion of age-standardized years of life lost due to self-harm was highest among males in Lithuania (4.1%) while the highest proportion due to substance use-related causes of death was among males in Estonia (7.3%). CONCLUSIONS: Our findings indicate that the burden of mental health-related mortality remained high and showed divergent temporal changes across the three countries. In the context of the Baltic States and other post-soviet countries, fractions of various external causes of death and alcohol-related causes of death should be considered in assessing the total burden of mental health-related mortality.

Varying frequency of vateritic otoliths in the Baltic herring Clupea harengus membras.

We report observations of vateritic crystallization in the sagittal otoliths of the Baltic herring Clupea harengus membras in the northern Baltic Sea. While the existence of vaterite in the calcium carbonate matrix of sagittal otoliths has been observed in various species globally, reports from the brackish Baltic Sea are few in number. Large variation in the frequency of vaterite in 1984, 1988, 1997, 2010 and 2017 was observed, suggesting that the phenomenon is not static and more long-term studies should be conducted in search of the ultimate causing factors.

Disentangling seasonal from maternal effects on egg characteristics in western Baltic spring-spawning herring Clupea harengus.

In marine fishes, the timing of spawning determines the environment offspring will face and, therefore, the chances of early life stage survival. Different waves of Atlantic herring Clupea harengus spawn throughout spring in the western Baltic Sea, and the survival of offspring from early in the season has been low in the most recent decade. The authors assessed changes in egg traits from early, middle and late phases of the spawning season to examine whether seasonal and/or maternal effects influenced embryo survival. At each phase, fertilized eggs of six to eight females were incubated at two temperatures (7 and 13°C), and egg size, fertilization success, mortality and time to hatch were recorded. A compilation of data from 2017 to 2020 spawning seasons indicated that mean total length of females decreased with progression of the season and increasing in situ water temperature. For the sub-set of females used in the laboratory study, early spawners were 7.6% larger and produced 14.2% larger eggs than late-spring spawners. Fertilization success was consistently high (>90%), and mortality to hatch was low (<3%). Neither the former nor latter were influenced by season, but both were influenced by maternity. This significant female effect was, however, not related to any maternal trait measured here (total length, Fulton's condition factor or age). There was no maternal effect on development rate at 7 or 13°C. The results suggest that intrinsic differences among females or among spawning waves are unlikely to markedly contribute to the poor survival observed for progeny from early in the season in this population and point towards other extrinsic factors or processes acting on eggs or early larval stages (e.g., seasonal match-mismatch dynamics with prey) as more likely causes of mortality.

A century of genetic homogenization in Baltic salmon-evidence from archival DNA.

Intra-species genetic homogenization arising from anthropogenic impacts is a major threat to biodiversity. However, few taxa have sufficient historical material to systematically quantify long-term genetic changes. Using archival DNA collected over approximately 100 years, we assessed spatio-temporal genetic change in Atlantic salmon populations across the Baltic Sea, an area heavily impacted by hydropower exploitation and associated with large-scale mitigation stocking. Analysis was carried out by screening 82 SNPs in 1680 individuals from 13 Swedish rivers. We found an overall decrease in genetic divergence and diminished isolation by distance among populations, strongly indicating genetic homogenization over the past century. We further observed an increase in genetic diversity within populations consistent with increased gene flow. The temporal genetic change was lower in larger wild populations than in smaller wild and hatchery-reared ones, indicating that larger populations have been able to support a high number of native spawners in relation to immigrants. Our results demonstrate that stocking practices of salmon in the Baltic Sea have led to the homogenization of populations over the last century, potentially compromising their ability to adapt to environmental change. Stocking of reared fish is common worldwide, and our study is a cautionary example of the potentially long-term negative effects of such activities.

DNA metabarcoding reveals trophic niche diversity of micro and mesozooplankton species.

Alternative pathways of energy transfer guarantee the functionality and productivity in marine food webs that experience strong seasonality. Nevertheless, the complexity of zooplankton interactions is rarely considered in trophic studies because of the lack of detailed information about feeding interactions in nature. In this study, we used DNA metabarcoding to highlight the diversity of trophic niches in a wide range of micro- and mesozooplankton, including ciliates, rotifers, cladocerans, copepods and their prey, by sequencing 16- and 18S rRNA genes. Our study demonstrates that the zooplankton trophic niche partitioning goes beyond both phylogeny and size and reinforces the importance of diversity in resource use for stabilizing food web efficiency by allowing for several different pathways of energy transfer. We further highlight that small, rarely studied zooplankton (rotifers and ciliates) fill an important role in the Baltic Sea pelagic primary production pathways and the potential of ciliates, rotifers and crustaceans in the utilization of filamentous and picocyanobacteria within the pelagic food web. The approach used in this study is a suitable entry point to ecosystem-wide food web modelling considering species-specific resource use of key consumers.

Evaluation of Methane Emissions Originating from LNG Ships Based on the Measurements at a Remote Marine Station.

We analyzed pollution plumes originating from ships using liquefied natural gas (LNG) as a fuel. Measurements were performed at a station located on the Utö island in the Baltic Sea during 2015-2021 when vessels passed the station along an adjacent shipping lane and the wind direction allowed the measurements. The ratio of the measured concentration peaks ΔCH4/ΔCO2 ranged from 1% to 9% and from 0.1% to 0.5% for low and high pressure dual fuel engines, respectively. The ratio of the measured concentration peaks of ΔNOx/ΔCO2 varied between 0.5‰ and 8.7‰, which was not explained by engine type. The results were consistent with previously measured on-board or test-bed values for the corresponding ratios of emissions. While the methane emissions from high pressure dual fuel engines were found to fulfill the goal of reducing the climatic impacts of shipping, the emissions originating from low pressure dual fuel engines were found to be substantially high, with a potential for increased climatic impacts compared with using traditional marine fuels. Taking only the global warming potential into account, we can suggest a limit value for the methane emissions; the ratio of the emissions ΔCH4/ΔCO2 originating from LNG powered ships should not exceed 1.4%.

70-Year Anthropogenic Uranium Imprints of Nuclear Activities in Baltic Sea Sediments.

A strongly stratified water structure and a densely populated catchment make the Baltic Sea one of the most polluted seas. Understanding its circulation pattern and time scale is essential to predict the dynamics of hypoxia, eutrophication, and pollutants. Anthropogenic 236U and 233U have been demonstrated as excellent transient tracers in oceanic studies, but unclear input history and inadequate long-term monitoring records limit their application in the Baltic Sea. From two dated Baltic sediment cores, we obtained high-resolution records of anthropogenic uranium imprints originating from three major human nuclear activities throughout the Atomic Era. Using the novel 233U/236U signature, we distinguished and quantified 236U inputs from global fallout (45.4-52.1%), Chernobyl accident (0.3-1.8%), and discharges from civil nuclear industries (46.1-54.3%) to the Baltic Sea. We estimated the total release of 233U (7-15 kg) from the atmospheric nuclear weapon testing and pinpointed the 233U peak signal in the mid-to-late 1950s as a potential time marker for the onset of the Anthropocene Epoch. This work also provides fundamental 236U data on Chernobyl accident and early discharges from civil nuclear facilities, prompting worldwide 233U-236U tracer studies. We anticipate our data to be used in a broader application in model-observation interdisciplinary research on water circulation and pollutant dynamics in the Baltic Sea.

Effects of first intermediate host density, host size and salinity on trematode infections in mussels of the south-western Baltic Sea.

Trematode prevalence and abundance in hosts are known to be affected by biotic drivers as well as by abiotic drivers. In this study, we used the unique salinity gradient found in the south-western Baltic Sea to: (i) investigate patterns of trematode infections in the first intermediate host, the periwinkle Littorina littorea and in the downstream host, the mussel Mytilus edulis, along a regional salinity gradient (from 13 to 22) and (ii) evaluate the effects of first intermediate host (periwinkle) density, host size and salinity on trematode infections in mussels. Two species dominated the trematode community, Renicola roscovita and Himasthla elongata. Salinity, mussel size and density of infected periwinkles were significantly correlated with R. roscovita, and salinity and density correlated with H. elongata abundance. These results suggest that salinity, first intermediate host density and host size play an important role in determining infection levels in mussels, with salinity being the main major driver. Under expected global change scenarios, the predicted freshening of the Baltic Sea might lead to reduced trematode transmission, which may be further enhanced by a potential decrease in periwinkle density and mussel size.