Volume 39 (2010): Issue 4 (December 2010)

The aim of this study was to distinguish the early succession stages of the fouling community in Puck Bay at depths of 3-7 m, to evaluate its biodiversity and to find the point at which the biodiversity of the assemblages achieved similarity. The depth at the study site was 8 m. The investigation lasted from 24 July to 22 September 2008 (61 days) when the colonisation and succession process of fouling communities is most intensive. During this period five sets of samples were collected. The investigations were focused on sessile organisms that established themselves on 105 PVC settlement panels (15 × 15 cm, 0.2 cm thick), 21 panels being deployed at each of five depths - 3, 4, 5, 6 and 7 m. A total of twelve sessile taxa and eight mobile (accompanying) taxa were identified over the course of the experiment. The panels became overgrown with fouling organisms in a characteristic manner - a layer of barnacles became covered with a layer of mussels. This type of community development created a double-layered structure (multi-strata growth). Assemblages reached a thickness of 2 cm as a result of the stratified fouling process. The species diversity was highest on 12 August (the first sampling day) at 7 m depth. Biodiversity differences during the study indicated that communities from all examined depths in Puck Bay became similar after a two-month colonisation period. By the end of the study Balanus improvisus and Mytilus trossulus were dominant in the communities at all depths.

Seasonal changes in gametogenesis, spawning behaviour and morphometric parameters of Macoma balthica and Mytilus trossulus from two depth zones in the Gulf of Gdańsk (Southern Baltic Sea) were investigated. The studies allowed the authors to make observations of the ecophysiological features of both species and revealed major differences in the weight index between deep and shallow water subpopulations. Both condition and gametogenesis probably depend mainly on the availability of nutrients and on temperature changes. The data showed that Mytilus trossulus spawned earlier at the shallow water station than at the deeper one. No differences were observed between the run of the Baltic clam's reproductive cycle at 10 m and at 75 m depths.

In the present work we have studied some of the indicators of oxidative damage of the digestive gland tissue of two populations of mussels Mytilus galloprovincialis: native mussels cultured in an aquaculture farm and contaminated mussels collected from the polluted marine area of the French Mediterranean coast located nearby Tamaris and La Seyne-sur-mer - small towns in close proximity to Toulon.

The phytoseston flora and heterotrophic bacteria from the two intersecting rivers were studied during the intensive water flow (from October 2006 to May 2007). The physical and chemical measurements indicated that the water quality in the rivers regarding their purity, had slightly improved in the Nielba River and deteriorated in the Wełna River, at the sites behind the intersection zone. It was in the agreement with the studied phytoseston diatom communities (dominated by eutraphentic taxa). Phytoplankton during the winter months was dominated by Aulacoseira granulata. The importance of species from the genera Oscillatoria, Planktolyngbya, Tychonema, Planktothrix, Scenedesmus/Desmodesmus, Nitzschia and Fragilaria increased in spring and autumn. Heterotrophic bacteria occurred in considerably higher numbers in the Wełna River than in the Nielba River, with a significant decrease in the waters of the Wełna River behind the river-intersection. All analyses revealed that the waters in the Wełna River were more polluted with organic compounds than in the Nielba River locations.

The aim of this study is to present short-term changes in the spatial structure of water vegetation in Lake Rotcze. Field studies were carried out during the growing seasons of 2000 and 2005. The obtained results allowed to estimate the following parameters that characterize the spatial structure of macrophytes: species frequency in particular ecological groups, the average vegetation cover in these groups, the average cover of particular species, both in the whole reservoir and in different depth ranges, as well as the PVI (Percent Volume Infested) coefficient for ecological groups. The frequency and cover of some species and ecological groups of macrophytes changed during the study period.

The species structure of epizoic communities of Rotifera was analyzed on three species of freshwater bivalves: Anodonta anatina (Linnaeus), A. cygnea (Linnaeus) and Unio tumidus (Philipsson) from lakes and rivers of north-eastern Poland. Epizoic rotifer communities were abundant and relatively rich in species. The communities were mostly built of common littoral species, like Colurella uncinata, Lecane flexilis, Lepadella quadricarinata, Ptygura melicerta. They were accompanied by species typical for pelagic waters (e.g. Trichocerca pusilla, T. similis). Bivalves inhabiting outflows of rivers from Knyszyn Forest had the most diversified and abundant epizoic communities. Large differences were also observed as regards particular species occurrence in different habitats. Maximum numbers of Ptygura melicerta living on the surface of bivalves from rivers accounted for 150 individuals per bivalve specimen, whereas those living on animals from lakes - up to 10 individuals. All studied bivalves were colonized by very large numbers of bdelloids.

In the year 2008, studies on ichthyofauna were carried out in the Kończak stream. The stream was divided into four sections representing the variability of the water course. In each section, a research segment (100-150 meters long) was defined. In the ichthyofauna structure analysis, the indices of quantitative biocenotic domination and biomass were used. Furthermore, on the basis of the obtained data, the Shannon-Wiener indices of species diversity (H), as well as the abundance and the biomass (ABC index) were calculated. Altogether, in all research localities, 667 fish specimens were collected, with a total weight of 8,760 g and classified into 19 species. The caught fish were classified into 8 reproductive groups. Significant differences in the species composition and the number of fish were recorded between the particular sections. The number of species occurring in the studied sections oscillated between 2 and 17. The richest ichthyocenoses were recorded in the transitional and forest sections characterized by a comparatively small transformation of the habitats and good environmental conditions. In the remaining two sections, located in the middle and in the upper stream course, there was a distinct impoverishment of ichthyocenoses caused by the decreased attractiveness of the habitats.

Investigations of the distribution of benthic macroinvertebrates in Lake Czarne were conducted in fall 2005 and spring 2006. Samples were taken in three transects (at a depth of 0.5 m and at 5 m intervals).

It was noted that macrobenthos only inhabit depths to 10 m. Laminar sediments from 15 m to 29 m indicate that macrobenthos never inhabit the deepest part of the lake in spite of temporary oxygen abundance (between 15 and 20 m during the winter and spring mixing periods). The largest diversity and biomass of macrozoobenthos was observed in the littoral zone at a depth of 0.5 m. At a depth of 5 m in the characean stands and at a depth of 10 m the number and biomass of benthic macroinvertebrates were significantly smaller. The reason for the decrease of benthos density seems to be gradual oxygen depletion.

Relationships between ciliates and the presence of emergent and submerged vegetation were studied in a shallow lake in eastern Poland. Samples were collected in zones of Phragmites, Typha, Batrachium, Elodea, Stratiotes and from the open water zone. The abundance and biomass of ciliates were significantly higher at sites with structurally most complex plants than in the open water or sparsely vegetated sites. The redundancy analysis indicated that bacterial abundance and total organic carbon were the most influential variables that determine the distribution of ciliates. However, chlorophyll a and P_tot have a lesser influence on the distribution of these microorganisms. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of three vegetation zones of sparse stem structure and the open water zone, the second group comprised submerged macrophyte species, which were more complex.

Studies on the role of Ceratophyllum demersum L. as a substratum for epiphytic midges in relation to lake status were conducted within two shallow polymictic lakes of Polesie Lubelskie. Lake Skomielno is classified as macrophyte dominated (MD), clear water state and Lake Syczyńskie represents phytoplankton dominated (PD), turbid water state. The results demonstrated that lake status is a determinant of community composition of epiphytic chironomids. Both species richness and abundance showed significantly higher values in the macrophyte dominated lake. The studied ecosystems differ in the composition of dominant chironomid taxa. In the clear state lake, the group of dominants included four taxa: Psectrocladius sp. (gr. sordidellus), Glyptotendipes sp., Ablabesmyia phatta and Paratanytarsus austriacus, the contribution of which changed during the studied months. In the turbid state lake two midge taxa dominated: Cricotopus sp. (gr. sylvestris) and Endochironomus albipennis. The CCA ordination showed the important differences between the studied lake types. In the MD lake, four environmental factors (temperature, chlorophyll-a, total P, P-PO₄) influenced mostly the distribution and composition of epiphytic chironomids. In the MD lake, five variables (periphyton biomass, total suspension, N-NH₄, total P, pH) affected the structure of midges.

Experimental research conducted on bottom sediments from the eutrophic Lake Rusałka (Poznań, Poland) indicated that the phosphorus release process has a significant influence on the functioning of the ecosystem. Internal loading was very intense in the deepest part of the lake, where it reached up to 29.84 mg m^-2 d^-1 P under anaerobic conditions. This part of the lake, however, was insignificant to overall internal loading. The highest loading was from the lake shallows, which covered 92% of the bottom area. Total mean annual loading to the ecosystem was 1214.5 kg year^-1 P, i.e., 3.31 g m^-2 year^-1 P.

This paper reports the results of Mn accumulation in two species of green algae: Chara globularis and Chara hispida. The results of laboratory and field experiments show a rapid accumulation of Mn by charophytes and demonstrate that deposit formation on the plant surface in the so-called adsorption phase occurs in Mn accumulation. Both species can be an important factor in Mn circulation in lakes.

One hundred thirty eight taxa of plankton algae were identified in the Żur Reservoir (Cyanoprokaryota 27, Dinophyta 5, Euglenophyta 4, Chrysophyceae 6, Bacillariophyceae 40, Chlorophyta 56). The biomass of spring and summer plankton consisted mainly of diatoms. Based on the species composition, phytoplankton biomass, concentration of chlorophyll a and TSI, the Żur Reservoir was generally classified as moderately eutrophic with distinct trophic diversification of the water at particular studied sites.

The present study describes for the first time the toxin production by Microcystis aeruginosa blooms in three rainwater ponds in Saudi Arabia. The cell density of M. aeruginosa correlated with chlorophyll-a, temperature and nutrient concentrations. Microcystis blooms produced the hepatotoxin microcystin (MCYST) with concentrations of 0.988-3.04 mg g^-1 dry weight, and a toxin profile consisting mainly of MCYST-RR, -YR and -LR. MCYSTs were also detected in pond waters at levels exceeding the WHO guideline value (11.2-34.6 μg l^-1). The study suggests the monitoring of toxic cyanobacteria in such potable water sources to protect the public from potent toxins.

Variations in physical and chemical conditions were investigated at Wadi Al-Arab Dam Reservoir (Jordan). Mean surface water temperature was 22.5°C and two distinctive temperature layers, epilimnion (down to 15 m, mean temperature 28.6°C) and hypolimnion (down to 35 m, mean temperature 21.1°C) were recognized in May. Minimum water transparency was recorded at 32 cm in July and maximum at 135 cm in August. The mean surface pH (8.0) and salinity (1.54 mg l^-1) showed no pattern of variation, with pH values of 9.31-8.1 and 5.1-3.1 recorded between February and July at 0-15 m and 15-35 m, respectively; and higher values of salinity (1.88 mg l^-1 and 1.84 mg l^-1) in the wet season. Electrical conductivity values ranged between 912 and 1257 μS cm^-1, with the highest values in summer. Records at station I and II showed a mean total alkalinity of 541.04 mg l^-1 CaCO₃ and dissolved oxygen (DO) levels of 6.2-8.9 mg l^-1 with the observation of the highest (8.0 mg l^-1) and lowest (4.0 mg l^-1) DO values in April at the surface and 15 m, respectively. In May, DO values dropped from 7.31 mg l^-1 in the upper layer to 3.85 mg l^-1 in the deepest layer. Nutrients as nitrate revealed minimum (0.7 mg l^-1 N-NO₃) and maximum (30.4 mg l^-1 N-NO₃) concentrations at the surface in station I and II, respectively. Levels of P-PO₄ were also high at stations I and II (0.73 mg l^-1 PO₄ and 1.02 mg l^-1 PO₄) in May and June, respectively. However, the minimum value (0.14-0.16 mg l^-1 PO₄) was recorded in October at both stations. Disolved reactive silica (DRS) levels showed low values of 2.55-11.46 mg l^-1 (station I in June) and 2.33-7.60 mg l^-1 (station II in May and December), respectively.