Comparative endocrine disruptive effects of contaminants in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea

We investigated variables related to thyroid, vitamin A and calcitriol homeostasis, immune function and tumour development in ringed seals (Phoca hispida) from the polluted Baltic Sea and a less polluted reference location at Svalbard, Norway. We also examined the relationships between the biological variables and the concentrations of persistent organic pollutants (POPs) and their hydroxylated (OH) metabolites. Our data show higher plasma concentrations of free triiodothyronine (T3), and ratios of free and total T3 in Baltic seals as compared to Svalbard seals. Baltic seals had also higher hepatic mRNA expressions of deiodinase-I, thyroid hormone receptor β, retinoic acid receptor α, growth hormone receptor and interleukin-1β compared to Svalbard seals. Levels of plasma retinol were lower in the Baltic seals as compared to Svalbard seals. No geographical difference was observed for other thyroid hormone levels and hepatic retinoid levels. Ratios of free and total T3 were positively correlated to OH-POPs in plasma. The results of the present study suggest that endocrine homeostasis may be affected by contaminant and metabolite exposure in the Baltic ringed seals with respect to circulating hormones and retinol and hepatic mRNA expressions. In addition, OH-POPs may putatively produce the disruption of thyroid hormone transport in plasma.     

Broad-scale patterns of abundance of non-indigenous soft-bottom invertebrates in Denmark

Quantifying the broad-scale distribution and abundance of non-indigenous species (NIS) is necessary to provide accurate estimations on impacts of invasions, to prioritize research, and to guide national management. Sediment grab-sampling is a standardized method for monitoring marine benthos. In Denmark, ~45,000 grab-samples were collected from 1970 to 2005. Using these samples, we compared densities of NIS and native species among 27 broad spatio-temporal groupings. Eight known NIS and one ‘cryptogenic species’ (the polychaete Neanthes succinea) were found in the samples. Most were present in low abundance, but the bivalve Mya arenaria, likely introduced by the vikings from North America, was particularly abundant. M. arenaria was found in ca. 20% of all samples and was among the 10 most common species in all of Denmark. M. arenaria’s high abundance, high filtration capacity and importance in food-web interactions, suggest that this species has dramatically impacted shallow coastal ecosystems in Denmark. The polychaete Marenzelleria viridis, the gastropod Potamopyrgus antipodarum and N. succinea were also widespread and abundant, and they too are likely to have had broad-scale impacts. In conclusion, 28% of grab-samples collected in Denmark over 35 years were affected by some degree of NIS or cryptogenic species, suggesting that centuries of human-mediated transfer of organisms has had a profound impact on the ecology of soft-bottom systems in Denmark.     

Cell culture and karyotype of Sakhalin sturgeon Acipenser mikadoi

A cell culture of rare and threatened species of Sakhalin sturgeon Acipenser mikadoi was established from a fragment of the pectoral fin and neighboring tissues. Initially, the culture consisted of different cell types including typical fibroblasts as well as cells of epithelial origin, myofibroblasts, etc. After approximately five passages, the culture largely consisted of cells with fibroblast morphology. Under normal culture conditions, these cells grew for more than one year at a constant rate and passed about 80 population doublings. In the absence of serum, cells entered the state of proliferative quiescence (G₀-state). When cultured without medium replacement for a long period of time, cells fused to form myofibers of about 1 cm in length. These myofibers could branch and acquired cross striation with time. About forty days after myofibers emerged, they degenerated, lost their shape, detached from the substrate, and finally died. The induction of adipogenic differentiation arrested cell proliferation and introduced lipophilic inclusions formed in a minor fraction of cells. The number of these inclusions was low, and cells with inclusions demonstrated various morphology distinct from typical adipocytes. The induction of osteogenic differentiation gave rise to cells that produce mineralized extracellular matrix and bone nodules. Chromosome analysis revealed a set of chromosomes typical for “high chromosome” sturgeon species. The variation in the chromosome number was very high (mean, 247 ± 33; modal value, 248). The analysis involving AT- and GC-specific fluorochromes has demonstrated that the telomeric and centromeric regions of all chromosomes are enriched in GC content. The distribution of AT- and GC-rich sequences along the chromosomes was heterogeneous. Long chromosomes were preferentially stained by the AT-specific dye, whereas small chromosomes demonstrated brighter fluorescence after 7-amino-actinomycin D staining; in particular, several small chromosomes fluoresced extremely brightly. This work is the first report of cell culture and karyotype analysis of Sakhalin sturgeon.     

Salinity gradient shapes distance decay of similarity among parasite communities in three marine fishes

Published data were used to compare the distance decay of similarity in parasite communities of three marine fish hosts: Atlantic cod Gadus morhua, the dab Limanda limanda and the flounder Platichthys flesus in two adjacent areas that differ with respect to the strength of a salinity gradient. In the Baltic Sea, which exhibits a strong salinity gradient from its connection with the North Sea in the west to its head in the north‐east, parasite communities in all three fish hosts showed a significant decline of similarity with increasing distance. In contrast, among host populations in the North Sea, which is a fully marine environment, there was no such decline or only a weak relationship. The results suggest that environmental gradients like salinity can be strong driving forces behind patterns of distance decay in parasite communities of fishes.     

Changes in Phytoplankton Biomass and Nutrient Quantities in Sea Ice as Responses to Light/Dark Manipulations during different Phases of the Baltic Winter 2003

The response of Baltic Sea ice communities to changing light climate was studied in three subsequent 3 week in situ experiments on the SW coast of Finland. The investigation covered three different winter periods, short day with low solar angles leading to limited light in the ice, late winter with deep snow cover and early spring with melting snow and increasing light availability. The experimental setup consisted of transparent (no snow) and completely darkened (heavy snow cover) plexiglass tubes in which the ice cores were incubated in situ from 1 to 2 weeks. Changes in the concentrations of inorganic nutrients (NO₃⁻-–N, PO₄³⁻-–P, SiO₄⁻-–Si) and chlorophyll-a concentration in the phytoplankton community composition were recorded as responses to different light manipulations. Changes in inner ice light intensity in untreated ice as well as the temperature both in air and ice were recorded over the entire study period. Increased irradiance in late winter/early spring and during meltdown affected the chlorophyll-a amount in the sea ice. During these periods the phytoplankton community in the top layers decreased possibly as a consequence of photo-acclimation. Closer to the bottom of the ice, however, the increased inner ice light intensity induced algal growth. Complete exclusion of light stopped the algal growth in the whole ice column. Darkening the ice cores also slowed down the ice melting opposite to accelerated melting caused by increased light. The significant differences found in nutrient concentrations between the light and dark treatments were mostly explicable by changes in algal biomass. No obvious changes were observed in the phytoplankton community composition due to light manipulation, diatoms and heterotrophic flagellates dominating throughout the study period.     

Towards better Understanding of Successful Management of the Gulf of Riga Herring Stock

The Baltic herring is one of the key elements of the pelagic ecosystem of the Baltic Sea, being of the most important commercial species of the sea. The structure and dynamics of herring populations (stocks) have been assessed and managed on international level since 1970s. Since 1990, all local herring populations have been combined and assessed as one stock (Central Baltic Herring in Sub-divisions 25–29 and 32). However, the continuously decreasing trend in stock biomass throughout almost 30-years period of observations indicates the failure of the stock management implementation of the scientific advice. The separate assessments of different stocks and results of hydro-acoustic surveys of different sub-units (herring in Sub-divisions 25–27, Sub-divisions 28, 29 and 32 and the Gulf of Riga herring) have revealed rather different situation within combined assessment unit: e.g. fishing mortality of the Gulf of Riga herring has decreased while a sharp increase in mortality is observed in the herring stocks of the North-eastern Baltic (Sub-divisions 28, 29 and 32). At the same time stock abundance and biomass of the Gulf of Riga herring have increased to record high in early 2000s allowing also higher catches. It is concluded that only separate analytical assessment of local populations combined with regular acoustical surveys and following different protection measures have proved to be a successful way in managing the herring stocks. Joint assessment and management of several populations with different structure and dynamics as one combined stock do not allow revealing the real situation and trends in its parts.     

Linking denitrifier community structure and prevalent biogeochemical parameters in the pelagial of the central Baltic Proper (Baltic Sea)

The oxic-anoxic interface of the water column of the Gotland Basin (central Baltic Sea) is characterised by defined biogeochemical gradients and is hypothesised to be a zone of pronounced denitrification. Our aim was to analyse the composition and distribution of pelagic denitrifying microorganisms in relation to the physico-chemical gradients in the water column. PCR-amplified nirS genes--coding for dissimilatory nitrite reductase--were analysed as functional markers by terminal restriction fragment length polymorphism and cloning. The overall nirS diversity was low, with the lowest levels found at the oxic-anoxic interface. Only a few terminal restriction fragments dominated the denitrifier communities throughout the water column, and these could be assigned to several new Baltic Sea clusters that were revealed by phylogenetic analysis. The novel clusters were separated in two groups corresponding to the oxygen concentrations within specific layers of the water column. Gradients of prevalent biogeochemical parameters (H(2)S, NH(4) (+), NO(3) (-) and O(2)) largely determined the composition of the nirS-type denitrifier communities within the water column of the Gotland Basin.     

Effects of organic and inorganic nitrogen compounds on the activity of bacterial alkaline phosphatase

The stimulation of bacterial alkaline phosphatase activity (APA) by inorganic and organic nitrogen compounds was investigated in the southern Baltic Sea monthly between February and August 2001, by adding albumin, casein, leucine, ammonium, nitrate, ammonium + glucose or nitrate + glucose to 0.8 µm filtered seawater. The following questions were addressed: (1) Are there seasonal changes in the stimulation of APA by these substances?; (2) Does nitrogen alone stimulate this activity or only in combination with organic carbon?; (3) Is there a relationship between ambient nutrient concentrations and the degree of stimulation? The addition of the mentioned compounds stimulated the APA in bacteria to a high degree, however, there were seasonal variations. Stimulation was low in February and March but high from May to August when the stimulation, e.g., by ammonium + glucose, was up to 6000-fold higher compared with February. In most experiments, the addition of the amino acid leucine and of inorganic nitrogen alone resulted in an inhibition of the bacterial APA. A relationship between ambient nutrient concentrations and the stimulation of the bacterial APA was only observed for albumin, which correlated negatively with dissolved inorganic nitrogen (DIN) and phosphate concentrations and for casein, which correlated only with DIN. The results indicate that the regulation of bacterial APA and the DOP degradation can be significantly influenced by the availability of nitrogen and organic carbon.     

Early sex identification of 18‐month cultured beluga sturgeon (Huso huso) using ultrasonography,small surgery and plasma steroid hormones

Since sturgeons do not show clear sexual dimorphism particularly when are small in size, attempts were made to determine the best methods to identify early sex in farmed beluga sturgeon (Huso huso). The present study describes the ultrasonography, small surgery and plasma steroid hormone methods to determine gender at 18‐month fish, which no research has been conducted yet into the fish at such small ages. Twenty one cultured beluga sturgeon's gonad were imaged using an ultrasonograph unit with a 9–13 MHz linear transducer. Overall accuracy of sex determination using ultrasonography was 80.95%. Plasma testosterone (T) levels were significantly higher in males than in females whereas 17α,20βOH‐P levels were significantly higher in females than in males. Testosterone (T) and 17α,20βOH‐P were not correlated with morphometric parameters (TL, SL, W, CF) in 18‐month beluga sturgeon. Results of this study indicated that sex could be identified by each of ultrasonography, small surgery and analysis of blood plasma in such a small size (18‐month). Although direct observation was more efficient than the other methods, ultrasonography was the simplest and cost‐effective tool in sturgeon's sex determination compared to other methods, and the least invasive.