Volume 38 (2009): Edizione 4 (December 2009)

In this paper the relationship between temporal changes in the occurrence of water masses and Trichiuridae and Gempylidae larvae composition and distribution in the Southwest Atlantic ocean were analysed between 25° and 40° S. Ichthyoplankton was collected during the three expeditions of the Subtropical Convergence Project: Winter and Spring 1977, Autumn 1978 and Summer 1981, realized in the Southwest Atlantic waters. Oblique tows were conducted using a Hensen net with 250 μm mesh size. Steep salinity and temperature gradient were found, where the river outflows from La Plata river (Argentina) and Patos Lagoon (Brazil) met the Tropical Water over the continental shelf between 32 and 36° S. We examined 524 Hensen-net samples that contained about 283 larvae from five species of Trichiuridae and Gempylidae. The most abundant and frequent specie were Trichiurus lepturus Linnaeus 1758 and Diplospinus multistriatus Maul 1948. The mesopelagics species D. multistriatus, Nealotus tripes Johnson 1865 and Lepidopus altifrons Parin&Collette, 1993 were associated with Tropical Water. The benthopelagic T. lepturus and the epipelagic Thyrsitops lepidopoides (Cuvier 1832) were associated mainly with Coastal Water and Subtropical Shelf Water.

Three cores recovered from the Gulf of Gdańsk in 2006 contain magnetic spherules of different origins. According to their chemical compositions and morphological features the magnetic grains were divided into two groups: (1) anthropogenic spherules primarily composed of SiO₂, Al₂O₃ and Fe₂O₃; (2) Fe-oxide spherules of extraterrestrial origin. These two groups are present in the surface sediments, indicating they are products of both man-made pollution and an influx of extraterrestrial matter. The presence of anthropogenic dust in the marine sediments is a record of pollution from nearby industrialized areas. On the basis of the presence of these spherules a tool could be developed for studying sedimentation rates in the marine sediments. However more precise studies are required to develop this method.

In this study, the influence of a combination of different photoperiods and temperatures on the final maturation and social interactions in three-spined sticklebacks was investigated. Water temperature appears to be the principal signal affecting gonadal development and breeding activity of sticklebacks in pre-spawning and spawning periods. Males can mature independently of photoperiod and a stimulatory effect of high temperature is not diminished by light deprivation. On the other hand, low temperature can inhibit the development of secondary sexual characters in males exposed to long day or constant light. In females, lighting seems to be more decisive for complete maturation and the lack of light delays the maturation rate, even in high temperature. While kept under the same conditions, males mature quicker than females. The presence of light and visual information are crucial to establish the social position of individuals in the group. In light, a rigid social hierarchy with one dominant, sexually active male is observed. In constant darkness, however, several males in the group demonstrate every sign of sexual activity.

The mud crab is the only non-indigenous xanthid encountered in the River Odra estuary. In 2007-2008, the crabs were collected, using fish traps, to determine sex and to follow variations in individual weight and carapace length and width over a year. Sex-dependent differences in the crab morphometry were studied as well. The largest catch was that obtained in September (23.48% of the total number of 264 individuals) and October (31.82%). Male crabs accounted for 56.44% of the total number; males dominated in autumn (September-December) and spring (March, May, June) catches. Males showed significantly wider carapaces (16.81 ±3.98 mm; range: 5.60-22.90 mm) and mean individual weight (2.15 ±0.94 g; range: 0.15-3.93 g) than females (mean carapace width of 15.05 ±3.33 mm; range: 5.30-19.80 mm, and mean individual weight of 1.47 ±0.60 g; range: 0.13-2.56 g). Of the 11 morphometric characters analyzed, expressed in relative values (%), related to the carapace width, males showed significantly larger claw dimensions (CHL₁, CHW₁, CHH₁, CHL₂, CHW₂, CHH₂) and smaller abdomen widths (AW).

In this paper, the results of research on phytoplankton species composition along the 145 km section of the Lower Vistula are presented. The research was carried out during the growing season in 1998. All sites were located in the mainstream, both in the river and in the dam reservoir, which is situated in the middle part of the studied river section. As regards the number of species, diatoms and green algae were the most numerous. Most of the species were identified at the site located above the dam reservoir. The fewest number of species were identified at the sites below the reservoir. Damming the river, and therefore changing the water flow velocity, had a clear effect on the species composition and diversity of plankton algae.

During 2004 and 2005 research on the malacocenoses existing in oxbow lakes differ in terms of hydrological connectivity was conducted in the valley of the Łyna River. The results showed that the connection of an oxbow lake with the river is the key factor influencing the abundance and biomass of molluscs in the lake. Three types of oxbow lakes representing lentic, semi-lotic and lotic environments were considered. In the lentic oxbow lake Mollusca was dominated by Potamapyrgus antipodarum Gray, the semi-lotic by Viviparus viviparus L., and the lotic by Pisidium sp. The most hospitable conditions for the molluscs' development were found in the semi-lotic reservoir where contact with the river was maintained by backwater in the downstream arm. The separation of the reservoir from the river caused a total reduction of the Bivalvia representatives. Diversity of the malacocenoses resulted mainly from different abilities to adapt to temporary oxygen deficits. Each type of oxbow lake is characterized by an individual pattern of oxygen distribution. To avoid anaerobic conditions and enable the development of biodiversity in floodplains, water bodies should be supplied by well-aerated river water.

This study determined the numbers and distribution of heterotophic and lipolytic bacteria and the activity of lipases in the water of the Słupia River, in the section of the river that flows through the city of Słupsk. From spring to fall the mean number of heterotrophic bacteria remained at a relatively constant level (158.3 × 10³ cells cm^-3-169.4 × 10³ cells cm^-3), whereas in winter a sudden drop to only 18.3 × 10³ cells cm^-3 was found. The numbers of heterotrophic bacteria in the whole studied section of the river were similar. The mean number of lipolytic bacteria reached a maximum in spring (12.9 × 10³ cells cm^-3), was high in summer (10.5 × 10³ cells cm^-3), and reached a minimum (1.3 × 10³ cells cm^-3) in winter. Lipolytic bacteria accounted for only 5 to 8% of the total number of heterotrophic bacteria. No marked differences in the numbers of lipolytic bacteria were determined within the section of the river studied. The highest levels of lipase activity were determined in spring (18.9 nM MUF dm^-3 h^-1) and fall (19.9 nM MUF dm^-3 h^-1), while the lowest (11.0 nM MUF dm^-3 h^-1) were noted in winter. There were no differences in the level of activity of lipolytic enzymes among the sites studied.

Six small dam reservoirs in northeastern Poland, with different hydrologic and catchment characteristics were selected for research from March to October (2001-2003). There was a significant correlation between DOC and TP in the reservoirs and the water retention time (WRT). The highest values of electrical conductivity (EC) were recorded in reservoirs with an agricultural basin. In almost all reservoirs a statistically significant decrease of EC, compared to inflowing waters, was noted. Nitrates were substantially reduced in afforested catchment reservoirs. The highest TP concentration was recorded in a newly flooded reservoir. In reservoirs with long retention time, phosphorus sedimentation takes place more intensively. This caused phosphorus reduction in outflowing waters.

Forms of nitrogen (N-NO₃^-, N-NH₄⁺, N-org) and phosphorus (P-PO₄^-3, P-org) were investigated in ground and surface water as well as in precipitation and run-off. The highest concentration of all the investigated compounds was determined in the drain and in run-off. This investigation shows that afforestations and small ponds function as very efficient biogeochemical barriers with regard to N-NO₃^- and P-PO₄^-3. They do not, however, limit the spread of P-org.

The study aimed at estimating the reliability of river classification based on macrophytes under differentiated habitat conditions. The studies were carried out between 2002 and 2005, within the EU STAR project and two other local projects. Factors taken into consideration included: shading, habitat modification, and lengths of the survey sections. Polish lowland watercourses were surveyed. The analyzed streams represented a wide range of degradation. Several macrophyte-based metrics were evaluated, including major European systems (MTR, IBMR, TIM, MI, RI) and diversity metrics (number of species, Shannon diversity index, total cover). The reaction of the macrophyte-based metrics examined to habitat factors was compared. It was proved that some of the metrics appeared to be resistant to different sources of variability, thus confirming their usefulness for river monitoring.

Physicochemical and microbiological examinations were conducted on the meromictic Lake Starodworskie located in Olsztyn. The temperature profile revealed a characteristic, small increase in temperature at a depth between 13 and 14 m, and permanent anaerobic conditions in the deeper water layers. Accumulation of dissolved mineral substances enhanced the thermal stability of the lake waters; electrolytic conductivity values in the water deeper than 15 m oscillated within the range of 533 - 568 μS cm^-1.

The examination of total amounts of heavy metals (Hg, Cd, Cu, Pb, Cr, Ni, Zn) was conducted in the outflow from a sewage treatment plant and in the waters and sediments of ponds supplied with them. As the water passed through the pond system, a decrease of heavy metal concentrations in the post-treatment sewage water supplying the ponds was observed. The highest concentrations of heavy metals were found in the outflow from the sewage treatment plant and lower concentrations were observed in the water of pond 1 (except for Zn), which was the direct receiver of post-treatment sewage, while the lowest values were noted in the final pond. The concentration of heavy metals in the sediments decreased in consecutive ponds. The highest concentrations were determined in the sediment of pond 1 that received the post-treatment sewage directly from the sewage treatment outflow, whereas the lowest values were estimated in the sediments of pond number 4, which was the final pond in the system.

The aim of the study was to evaluate the trophic conditions of the waters of twelve small ponds based on the analysis of their physical and chemical parameters according to Carlson's Trophic State Index and OECD. Great differentiation in the trophic status of ponds located in different varieties of landscape was observed and ranged from mesotrophic to weak eutrophic conditions in mid-forest ponds and clay-pits, eutrophic conditions in pastoral ponds, and hypertrophic conditions in urban water bodies. Throughout the analysis, a number of limitations in the classification methods of trophic conditions in the examined water bodies were noted. The specific problems were the shallow depth of ponds, which often corresponded with the depth of the Secchi disc transparency, or the complete overgrowing of the pond water column by macrophytes.

This paper presents a current study on the morphology, genetic variability, and ecological requirements of the gametophytically diploid S. denticulatum (Bryophyta, Sphagnaceae). Its broad variations in morphology and physiology, coupled with its low genetic variability, may be explained by epigenetic remodeling in response to environmental heterogeneity.

Phenotypes initiated via a plastic response can be canalized in the stable and predictable conditions on the bottom of Lobelia lakes. The problem of the different development of these isolated populations is a matter for further taxonomic studies and discussion.

Taking into account the great physiological tolerance and massive development of S. denticulatum, predominantly in man-made and man-modified habitats, the question arises: how far should we go to protect this species? This is particularly important at sites where it threatens the survival of other protected plants.