Volume 41 (2012): Issue 2 (June 2012)

Populations of three sympatric species (Daphnia cucullata, Daphnia galeata, and Daphnia hyalina (Daphnia longispina complex)) inhabiting three lakes in northeastern Poland (Roś, Mikołajskie, Wigry) were checked for interspecific hybrids. Hybrid Daphnia coexisting with parental individuals were detected in each of the investigated lakes. Several classes of hybrids (F1, F2, backcrosses), including D. cucullata×galeata×hyalina individuals, have been detected. Hybrids constituted a substantial (13%–38%) part of the total abundance of individuals of the D. longispina complex. Deficiency of heterozygotes (hybrids) detected may indicate the existence of barriers for gene flow between the sympatric Daphnia taxa.

The middle course of the Neman River is the habitat of 120 water beetle species. Water beetles were most abundant in the Neman River, its major tributaries and oxbow lakes. They consisted of four synecological groups: rheobiontic and rheophilic organisms, type “a” and “b” stagnobionts. The diverse types of aquatic environments constitute faunal centers which, in addition to the specific and dominant Coleopteran populations, also feature migrational elements. The presence of close relations between the fauna of different environments indicates that they form a single, faunistically integrated hydrological system.

The article presents the research into the taxonomic diversity of cyanobacteria and algae, as well as the relationships between these organisms and the habitat conditions of certain water ecosystems varying in origin and location (both rural and urban reservoirs in the Lower Silesia region — Poland). Another issue addressed in the paper is the influence of ecological conditions and the origins of the reservoirs on the structure of phytoplankton. The RDA enabled to identify the most important biological parameters (the biodiversity of cyanobacteria and algae described using the Shannon-Weaver Index) and the physicochemical properties of the studied basins. The results distinguished four groups of basins (I — artificial basins within urban areas; II — old river-beds within urban areas; III — ponds in rural areas; IV — an old river-bed in forest areas). This distinction shows major relevance of the reservoirs’ origins and their presence in the landscape. Additional PCA and RDA analyses of the studied basins have shown that the biological parameters are more efficient in diversifying the basins in respect of their origins than the physicochemical parameters.

The species composition of phytoplankton and quantitative parameters of its abundance are indicators of ecological conditions in a water body. This paper deals with the analysis of phytoplankton in the Irkutsk Reservoir, which was formed more than 50 years ago on the Angara River flowing out of Lake Baikal. The level of phytoplankton development in the reservoir is directly dependent on the abundance of diatoms in Lake Baikal. The dominant assemblage of algal species is stable and consists mainly of diatoms, chlorophytes, and chrysophytes. Cyanobacteria are represented by a small number of species with low abundance. According to the composition of indicator species, the water in the lower reaches of the Irkutsk Reservoir can be classified as clean. The saprobity index in the open-water period is 1.2, increasing to between 1.3 and 1.5 in small bays. The values of phytoplankton biomass and chemical parameters of water recorded in 2008 indicate that the Irkutsk Reservoir is an oligotrophic water body. Its trophic status has not changed significantly since the time of impoundment (1956–1958).

The interactions of Ipomoea aquatica and Utricularia reflexa with phytoplankton densities were studied in a small water body in Zaria, Nigeria from June to November 2007. The negative effects of both macrophytes on 10 out of 15 phytoplankton taxa, including Staurastrum sp., Netrium sp., Ulothrix sp., Marssionella sp. and Closterium sp. were differentiated from other environmental effects. U. reflexa, on the other hand, showed positive associations with species like Actinocyclus sp., Palmellopsis sp., Spirotaenia sp., Microcystis sp. and Marssionella sp. Qualitative phytochemical screening and FT-IR analyses confirmed the presence of glycosides, anthraquinone, saponins, steroids, triterpenes, flavonoids, and alkaloids in Ipomoea aquatica and Utricularia reflexa. The observed variations in phytoplankton community dynamics were closely related to the presence of these macrophytes as well as the environmental conditions in the pond.

The aim of this study was to examine the community structure and vertical micro-distribution of psammonic ciliates in two lakes of different trophic status in eastern Poland. Additionally, the size and trophic structure of these microorganisms, and the influence of physical and chemical water parameters on their abundance, were analysed. Psammon samples were collected during spring, summer, and autumn of 2010. In each of the lakes samples were collected in the euarenal, higroarenal, and hydroarenal zones of the psammolittoral. In order to determine the micro-vertical distribution of ciliates, each sample was divided into two sub-samples: the upper part (0–1cm) and the lower part (1–2cm). The species diversity of ciliates decreased with depth. The tendency was particularly clear in mesotrophic lakes. Irrespective of the lake’s trophic type and arenal zones, significantly higher numbers and biomass of ciliates were recorded in the surface layer of the psammolittoral. The upper layer of sand was dominated by omnivorous taxa, whereas the deeper layer showed increases in the proportions of bacterivore species. The factors limiting the occurrence of ciliates are mainly concentrations of total organic carbon and nutrients.

The composition and the content of lipids, fatty acids and sterols during spawning (spring) in different tissues of herring Clupea harengus membras were compared with quantities of lipid compounds in abdomen muscle of brown shrimp Crangon crangon. The largest quantity of fatty acids in lipids (93.7%), was observed in fish muscle. The liver was characterized by a higher content and variety of sterols (about 4.6 times more than in fish muscle), and in fish sperm, additional fatty acids were identified and the highest amount of EPA and DHA (22% and 34% of fatty acids, respectively) was recorded. The brown shrimp, despite its small size, contained significantly more lipids than the Baltic herring per g of tissues. Fatty acids were at the same level (83% of the total lipids in shrimp muscle and 93.7% in fish muscle), but the amount of sterols was significantly higher in the muscle of shrimp (5.50 ±0.31 mg g−1, 17% of total sterols, n=10) than in fish muscle (1.33 ±0.04 mg g−1, 6.3% of total lipids, n=6). And thus, shrimp is a good source of food for higher trophic levels, and in consequence — a good source of PUFAs for humans. With these results we prove that shrimp and herring play an important role in the supply of EFAs, which has great pharmaceutical and medical benefits.

Cod (Gadus marrhua L), a fish caught in the Baltic Sea, is very popular with consumers. Research on the distribution of mercury in cod tissues and organs was conducted on a group of adult (27) and juvenile (49) individuals in the years 2006–09. Total mercury concentration values in mature cod were always, on average, 1.7 times higher than those in juveniles. The highest HgT concentrations were found in the heart, while the lowest ones were found in the gills and gonads. The essential age-specific differences manifest in a relationship between the mercury concentration in fish muscles and brain. Mature individuals, i.e. of length >80 cm, accumulated Hg in muscles, most likely in an attempt to protect the nervous system from toxic exposure. In young individuals, more mercury was concentrated in the brain than in the muscles.. The distribution of HgT in organs as well as the low value of the [HgT]liver/[HgT]muscle ratio testify to relatively low-level mercury contamination in southern Baltic waters.

Sulfur is an element commonly occurring in the environment. It is present in the atmosphere, in the hydrosphere, and in live organisms; it is one of the most important physicochemical and geological indicators. Depending on the natural conditions, sulfur compounds in the environment may play the role of electron acceptor or donor in the redox processes. These compounds influence the ion concentration and ion balance in benthic sediments. They also determine the speciation, bioavailability and toxicity of heavy metals. Comprehensive knowledge of the processes mediated by sulfur can be a valuable source of information about the past and present state of the ecosystem.

We conducted a snapshot study to check the importance of non-native Ponto-Caspian gobies (monkey and racer goby) in the diet of native obligate (northern pike, pikeperch) and facultative (Eurasian perch) predators in the Vistula River 3–4 years after the appearance of aliens. In total 71 fish with non-empty stomachs, taken randomly from net catches from various parts of the river were analyzed, including 32 pike, 20 pikeperch and 19 perch specimens. We found that gobiids prevailed in the diet of smaller (<30 cm standard length, SL) individuals of pike and pikeperch, as well as larger (>15 cm SL) specimens of perch, although the effect of predator size on the presence of gobiids in the diet was not significant in the case of perch. Our results indicate that gobiids as a prey fish can stimulate considerable changes in local food webs, which require further studies.