Volume 46 (2017): Issue 4 (December 2017)

The main objectives of this work were to investigate the range of habitat conditions (in terms of water chemistry and hydromorphological parameters) at sites colonized by Elodea canadensis and to analyze the species composition of communities with this plant species. We analyzed physicochemical, hydromorphological and biological data from 1135 sites located in Polish rivers to identify environmental factors that determine the occurrence of Elodea canadensis. Canadian waterweed was present at 18.1% of the analyzed river sites, located mainly in the lowlands (26.2% of all lowland sites).The results show that Elodea canadensis prefers moderately mineralized water (545 ± 329 μS cm⁻¹), rich in calcium and magnesium carbonates (174 ± 63 mg CaCO₃ l⁻¹, 84.1 ± 31.4 mg Ca²⁺ l⁻¹ and 11.1 ± 6.4 mg Mg²⁺ l⁻¹), with moderate concentrations of chlorides and sulfates (38.9 ± 59.1 mg Cl^- l⁻¹ and 62.3 ± 50.9 mg SO₄²⁻ l⁻¹) and in terms of nutrients, it prefers water from moderately rich to mesotrophic and eutrophic. This plant has high light requirements and grows mainly in unshaded sections of shallow rivers. The studied species avoids sections of rivers strongly transformed and those with reinforced banks and bottoms. Canadian waterweed occurs mostly in the company of vascular macrophytes associated with slow-flowing rivers with sandy bottom material, indicating mesotrophic and eutrophic water.

Substrate specificity of the periphyton community is usually underestimated in both periphyton ecology and biomonitoring studies, thus different kinds of both natural and artificial substrates (of organic and inorganic origin) are employed. Periphyton colonization and successional trajectories are particularly debatable processes when different kinds of substrates are considered. In our field experiment, we deployed four kinds of artificial substrates (two inorganic ones – glass and ceramic, and two organic ones – willow and yew wooden tiles) for the development of periphyton in an urban reservoir referred to as Lake Savsko (Belgrade, Serbia). We comparatively investigated the structure, colonization process, diversity and successional trajectories of periphyton. We also assessed the relationship between the dynamics of algae growth forms (ecological groups) on different substrates and selected abiotic limnological factors. Our objective was to determine whether the type of substrate affects periphyton characteristics at various levels and whether an artificial substrate potentially affects the bioindication capacity of ecological groups. We concluded that all substrates behave similarly at the level of structure and colonization phases, but when considering diversity and successional trajectories, the substrate specificity was demonstrated. Our results suggest that communities developed on inert substrates (glass and ceramic) could provide more realistic insight into complex environmental changes.

The abundance and horizontal distribution of three pteropod species, Limacina helicina, Limacina retroversa and Clione limacina were examined in the western entrance of the Barents Sea (Polar Front region) in August 2011. Sixteen samples were collected from 8 sampling sites located along a latitudinal transect. The southern part of the study area (south of 73°N) was dominated by L. retroversa, while L. helicina was mostly observed north of 73°N. Surface water temperature differences between the coldest and the warmest station were around 8°C. The highest density of L. retroversa was found in the south, near the Norwegian coast (nearly 52 000 ind. 1000 m⁻³), while the highest density of L. helicina was observed in the region of the Arctic water masses (nearly 13 000 ind. 1000 m⁻³). The sampled population of pteropods comprised mainly juvenile stages. Redundancy analysis (RDA) of the relationships between environmental factors (mean and surface salinity, mean temperature, sampling depth, chlorophyll concentration) and the population structure showed that mean temperature was the most important factor in the study area, explaining 70.5% of the pteropod community variation.

The objective of this study was to compare the distribution patterns of macroinvertebrate species between the Northeastern Levantine Sea and the Northeastern Aegean Sea. A total of 157 hauls were carried out by commercial trawlers at depths ranging from 30 to 410 m in both areas. The result of SIMPER analysis shows clear differences between the two surveyed areas except for the 300-410 m depth range. Ninety five species were found in the Northeastern Aegean Sea and 100 species in the Northeastern Levantine Sea. Of these species, Pyrosoma atlanticum is newly reported for the Turkish coast. Forty three species were common to both areas.

Histology has been used in the past to investigate the effects of diseases and parasite infections in native mussel populations that are often used as sentinel species in coastal environmental monitoring and as stock in mariculture. This paper presents the first study of parasite diversity using cryosections of the Mytilus galloprovincialis Lamarck, 1819 digestive gland. Mussels were sampled across the annual cycle at two sampling sites: St. Andrew and ACI Marina in the Northern Adriatic (Croatia). The protozoan of the genus Nematopsis Schneider, 1892 (Apicomplexa, Gregarina) was detected in digestive tubules, while the turbellarian (Urastomidae) Urastoma cyprinae von Graff, 1913 was found in the connective tissue at the edge of the digestive gland. The filamentous fungus Alternaria sp. (Fungi, Ascomycota) was detected in epithelial cells of the digestive tubule in cryosections. Nematopsis sp. occurred with the prevalence ranging from 20 to 100%, and the intensity of infection in less than 30 oocysts in most of the cases. U. cyprinae was detected in mussels sampled at St. Andrew and had a prevalence of 20% in September. Conidia of Alternaria sp. were found in mussels sampled at St. Andrew in September and November. Cryosections provide a useful and affordable means for monitoring parasites and endobiotic fungi.

Hemicypris vulgaris Okubo, 1990, Stenocypris bolieki Ferguson, 1962 and Bradleystrandesia parva (Hartmann, 1964) are reported from a tributary of the Gönen River (Balikesir) in Turkey. Hemicypris vulgaris is reported for the first time from Turkey. The finding of Bradleystrandesia parva is especially important as its original description is brief and inadequate. This paper provides details of redetection of the three species and comments on their variability and possible cryptic speciation.

Dinophysis species are distributed worldwide and cause diarrheic shellfish poisoning (DSP). This paper documents the first successful culture of a Dinophysis (DAYS01) strain taken off Xiaoping Island, the Yellow Sea, China. The strain was identified as Dinophysis acuminata Claparède & Lachmann by morphological and phylogenetic analysis. The effects of temperature and different Mesodinium prey on the physiological and toxigenic characteristics of D. acuminata DAYS01 were also investigated. The results showed that the toxin concentration (toxin amount per ml of culture) increased with an increase in cell densities. Okadaic acid (OA), dinophysistoxin 1 (DTX1) and pectenotoxin 2 (PTX2) were the major toxin components of DAYS01, with the highest recorded toxin content of 5.66, 0.56 and 192.87 ng ml^-1 culture medium, respectively. The prey type significantly influenced the growth yield in Dinophysis cultures. There was an effect of prey on the total toxin content, suggesting that the origin or strain of ciliate directly impacted the D. acuminata blooms and the overall toxin concentration in the system

The aim of this work was to assess the adaptive capabilities of the spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) in the open coastal waters of the Baltic Sea. The results could help to predict the likely further expansion of this species and its colonization of brackish waters. The following aspects were discussed in the paper: the occurrence of the species in the Polish coastal zone of the Baltic Sea, the plasticity demonstrated in the body size of individual crayfishes, food preferences, hemolymph osmolality and reproduction in waters of different salinities, which enable the species to colonize brackish waters. In the Vistula Lagoon (salinity 2-3 PSU), where the population of O. limosus is stable, the length of individuals ranged from 77 to 118 mm. These crayfish mostly fed on fodder; the second and the third food preferences were crayfish abdominal muscle and green algae. O. limosus is a hyper-regulator in freshwaters and at low salinities (up to 13 PSU), and a hyporegulator at higher salinities (14, 21, 28, 35 PSU). Laboratory studies showed that the embryonic development of O. limosus at salinities of 3 and 7 PSU was normal and a high level of reproductive success was achieved. Salinity of 3 PSU is more favorable for the development of juveniles than 7 PSU. It seems to be just a matter of time before this crayfish starts to form populations in the brackish, coastal waters of the Baltic Sea.

Diatoms of the genus Surirella are considered to be a very diverse group, many of them are endemic species found in old lakes as well as in tropical regions worldwide. This study describes a new location of Surirella barrowcliffia. In 2005-2007, algological research on the taxonomic composition of benthic diatoms was conducted in the middle section of the Pilica River (Central Poland). A total of 23 benthic samples were collected from a single sampling site located in the town of Sulejów (159.8 km upriver). Altogether 242 diatom species were identified in the collected material. One of the most interesting taxa in this community was S. barrowcliffia. According to the information available in the world’s algological databases, such as Algaterra and AlgaeBase, S. barrowcliffia has so far been found only in England, France, Finland, northern Germany – in the Weser and the Kleine Wumme rivers, near Bremen, and in Romania in the Crapina-Jijila lake complex. S. barrowcliffia has not been recorded in the previous research conducted not only in the middle section of the Pilica River, but also in other Polish aquatic ecosystems.

In order to understand the silver eel migration behavior of the Japanese eel Anguilla japonica, the life history of both the yellow stage (immature stage) and the silver stage (early maturing stage) was examined during the silver eel migration period, using otolith microchemical analysis of strontium (Sr) and calcium (Ca) concentrations. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicate eels of several general categories of migratory histories, including sea eels (average Sr:Ca ratios, ≥ 6.0 × 10^-3), estuarine eels (average Sr:Ca ratios, 2.0 × 10^-3 ≤ Sr:Ca < 6.0 × 10^-3) and river eels (average Sr:Ca ratios, < 2.0 × 10^-3), based on the criteria reported previously in A. japonica. A significant negative correlation was observed between the gonadosomatic index (GSI) and the mean Sr:Ca ratios during the growth phase after recruitment. Gonads of river eels were more developed compared to eels with other migratory histories. It thus appears that the maturation level for the silver eel migration to the open ocean varies depending on the life history.