Ilmaston muuttuessa meriekosysteemien keskinäinen vuorovaikutus Euroopassa muuttuu

Uusin tutkimuksemme tuo vahvistusta näkemykselle, että Itämereltä Pohjanmereen purkautuvalla murtovedellä on aiemmin tiedettyä voimakkaampi vaikutus paitsi Pohjanmeren suolapitoisuuteen ja kasvi- ja eläinplanktonin määrään, myös silikaattiravinteen saatavuuteen Pohjanmeren ulappaekosysteemissä.</p

Long-term data reveal the associations of the egg quality with abiotic factors and female traits in the Baltic Herring under variable environmental conditions

In fish, the lipid resources of the female form a link between the environment and progeny, contributing to the contents of the egg yolk. Variation of the environmental conditions is therefore expected to affect the egg quality via maternal pathways, reflecting the female’s response to the environmental factors before spawning. We investigated the content of lipids and thyroid hormones in the ovary and eggs of the Baltic herring during 1988–2019, when salinity of the Baltic Sea first declined and then stabilized to a lower level, and winters varied between severe and mild. The total lipid resources of spawning females decreased by 40–50% during the study, and the ovarian lipid concentration followed this trend resulting in a decrease of the lipid content of eggs. The concentration of thyroid hormones in the ovary suggested a hormonal response in females to salinity and winter temperature and was observable also in the content of thyroid hormones in the eggs. A change in the egg lipid content took place approximately around 1998 (SE ± 3 years) suggesting that in declining salinity, egg quality was associated with salinity and intrinsic factors in the female, i.e., fecundity and amount of lipids deposited into the ovary. However, during the period of stable salinity, egg quality was mainly limited by the female’s lipid resources. As also the body size of the females decreased over the years, it is suggested that small body size can be a key phenotypic trait to reduce the environmental impact on egg quality in variable environmental conditions.</p

The blue mussel color polymorphisms and growth rates in the Archipelago Sea, northern Baltic Sea

The blue mussel (Mytilus trossulus × edulis) is one of the most abundant benthic animals in the Archipelago Sea in the northern Baltic. The mussel is considered a key species, because it participates in the biomass and nutrient cycles by filtering water, serves as a growth platform and is a food source for many organisms. The mussel exhibits a genetic polymorphism in its shell color, in which a recessive allele causes a dark blue color, whereas the dominant allele causes brown. Earlier studies have hypothesised about a relation between mussel color forms and growth rates. In this study, we examined the occurrence of the mussel’s color forms in the Finnish Archipelago Sea and investigated the differences in mussel growth rates between the color forms. We analysed 524 individuals from regional mussel populations representing four sampling sites with varying environmental conditions. The study revealed that presently the distribution of both color forms is relatively even. The dark blue color form indicated only a slight dominance in abundance at the study sites. We did not detect differences in growth rates among mussels of the color forms. This was likely due to a large variation in the individual growth rates of mussels. Instead, differences in the average growth rates among the sampling sites were observed. This indicated that other factors that limit the survival of mussels in the Archipelago Sea habitats, such as salinity and temperature, play an important role in the growth rates of the color forms. In the future, the dark blue form can likely be expected to be proportionally more common in the Archipelago Sea, if the global climate warming and seawater temperature together with turbidity increase continues as expected. Numerically the brown color form will be preserved because it can tolerate higher temperatures

Morphological abnormalities in gonads of the Baltic herring (Clupea harengus membras) in the northern Baltic Sea.

Reproductive disorders are a major environmental concern in the Baltic Sea, due to heavy anthropogenic influence and long- and short-term variations taking place in the natural environment. We report here an increasing prevalence of gonadal malformations in the Baltic herring (Clupea harengus membras),a key species of the Baltic ecosystem and important in commercial fishery.</p

Environmental conditions, population density, and prey type influence the lipid reserves of Baltic herring in the northern Baltic Sea

Change of climate is expected to influence the energy content of fish by affecting the environmental conditions  here lipids are produced, transferred, accumulated and consumed. We examined the lipid content of the Baltic herring (Clupea harengus membras) spawning in the Archipelago Sea during a period of declining salinity, high variability in temperature, and increasing population size in the Bothnian Sea. Contemporary samplings of zooplankton in the feeding area (Mäkinen et al. 2017) enabled comparisons of fatty acid (FA) composition between herring and its prey Limnocalanus macrurus, which forms a major source of energy in the Bothnian Sea in May-June (Rajasilta et al. 2015).</p

Formation of lipid reserves, fatty acid composition and reproduction of Limnocalanus macrurus (Copepoda, Calanoida) during summer in the Bothnian Sea, northern Baltic Sea

Limnocalanus macrurus is a cold-stenothermic copepod that in the Baltic Sea occurs abundantly in low-salinity areas, such as the Bothnian Bay and the Bothnian Sea, where it is one of the most important species of the pelagic ecosystem. Projections for the future of the Baltic Sea suggest that a further decline of salinity will enable the species to expand its distribution southward to the Central Baltic, where it eventually could replace copepod species, e.g. Pseudocalanus acuspes, having higher salinity requirements. Lipids may get a central role in this process as they are crucial in the production and transfer of energy in the food webs. We studied the formation of the lipid reserves in L. macrurus in the Bothnian Sea, with a special emphasis on the fatty acid composition in reproductive adults and their potential food. Our primary interest was the spring and summer season, as it is the main production and feeding period of the plankton community in the southern Bothnian Sea. The study was started at the time of the spring bloom of phytoplankton during May and it was continued until September, when the plankton production ceases.</p

Scenario simulations of future salinity and ecological consequences in the Baltic Sea and adjacent North Sea areas-implications for environmental monitoring

Substantial ecological changes occurred in the 1970s in the Northern Baltic during a temporary period of low salinity (S). This period was preceded by an episodic increase in the rainfall over the Baltic Sea Watershed area. Several climate models, both global and regional, project an increase in the runoff of the Northern latitudes due to proceeding climate change. The aim of this study is to model, firstly, the effects on Baltic Sea salinity of increased runoff due to projected global change and, secondly, the effects of salinity change on the distribution of marine species. The results suggest a critical shift in the S range 5-7, which is a threshold for both freshwater and marine species distributions and diversity. We discuss several topics emphasizing future monitoring, modelling, and fisheries research. Environmental monitoring and modelling are investigated because the developing alternative ecosystems do not necessarily show the same relations to environment quality factors as the retiring ones. An important corollary is that the observed and modelled S changes considered together with species' ranges indicate what may appear under a future climate. Consequences could include a shift in distribution areas of marine benthic foundation species and some 40-50 other species, affiliated to these. This change would extend over hundreds of kilometres, in the Baltic Sea and the adjacent North Sea areas. Potential cascading effects, in coastal ecology, fish ecology and fisheries would be extensive, and point out the necessity to develop further the "ecosystem approach in the environmental monitoring". (C) 2014 The Authors. Published by Elsevier Ltd.Peer reviewe

The blue mussel color polymorphisms and growth rates in the Archipelago Sea, northern Baltic Sea

The blue mussel (Mytilus trossulus × edulis) is one of the most abundant benthic animals in the Archipelago Sea in the northern Baltic. The mussel is considered a key species, because it participates in the biomass and nutrient cycles by filtering water, serves as a growth platform and is a food source for many organisms. The mussel exhibits a genetic polymorphism in its shell color, in which a recessive allele causes a dark blue color, whereas the dominant allele causes brown. Earlier studies have hypothesised about a relation between mussel color forms and growth rates. In this study, we examined the occurrence of the mussel’s color forms in the Finnish Archipelago Sea and investigated the differences in mussel growth rates between the color forms. We analysed 524 individuals from regional mussel populations representing four sampling sites with varying environmental conditions. The study revealed that presently the distribution of both color forms is relatively even. The dark blue color form indicated only a slight dominance in abundance at the study sites. We did not detect differences in growth rates among mussels of the color forms. This was likely due to a large variation in the individual growth rates of mussels. Instead, differences in the average growth rates among the sampling sites were observed. This indicated that other factors that limit the survival of mussels in the Archipelago Sea habitats, such as salinity and temperature, play an important role in the growth rates of the color forms. In the future, the dark blue form can likely be expected to be proportionally more common in the Archipelago Sea, if the global climate warming and seawater temperature together with turbidity increase continues as expected. Numerically the brown color form will be preserved because it can tolerate higher temperatures.</p

The prevalence of Corynosoma parasite worms in the great cormorants and the Baltic herring in the northern Baltic Sea, Finland

During 2014–2019, the prevalence of Corynosoma spp., a parasite species in great cormorants (Phalacrocorax carbo spp.) and in Baltic herring (Clupea harengus membras), was studied in the Archipelago and the Bothnian Seas of the northern Baltic Sea. These results suggest that cormorants may act as a definitive host for these acanthocephalan parasites. Adults were more infected with the parasites than juveniles, which could be due to their larger size. A lower prevalence of Corynosoma spp. in juveniles may be because smaller cormorants eat smaller fish that have less parasites. We found that the most abundant corynosoma species in both the Baltic herring and cormorants were Corynosoma semerme, whereas only a few individuals of C. strumosum and only one C. magdaleni were found. The prevalence of corynosoma in herring increased from 2014 to 2018, and individuals in the Bothnian Sea were infected less frequently than herring in the Archipelago Sea. Results also showed that infected herring individuals were generally larger than non-infected individuals, which could be explained by their size and their feeding habits. Currently, the changing environment of the Baltic Sea may cause an effect on the herring making them more susceptible to infections. Our results, therefore, emphasize the importance of the regular monitoring of infections and the parasite-host relationships in the Baltic Sea