Volume 38 (2009): Issue 1 (March 2009)

In 2006 the spatial distribution and seasonal variations in chlorophyll concentration were measured, at about two-week frequency, in Lake Gardno. In general, chlorophyll concentrations in the central part of the lake were high throughout the growth season. The minimum chlorophyll concentration was recorded in March (7.5 mg m^-3), and the maximum value in September (303 mg m^-3). Higher chlorophyll concentrations and lower temporal variability were measured in the central part of the lake, compared to lower concentrations and higher variability in the vicinity of the Łupawa River input to the lake. Chlorophyll concentrations were measured fluorometrically along several vertical and horizontal profiles, enabling direct observations of the dynamics of changing chlorophyll concentrations in Lake Gardno throughout the year.

Two rivers situated in Central Poland, the Bzura and the Pilica, were selected for analysis of their water quality using benthic diatom species as indicators. The Bzura River has previously been strongly contaminated with organic pollutants, while the Pilica River has been classified as having good water quality. Samples were collected from nine sites along the Bzura in April 2003 and seven sites along the Pilica in April 2006. The main aims of the study were to determine the dominant diatom species present in the rivers and to assess their usefulness as biological indicators. Water quality of the rivers was estimated on the basis of the SPI - Specific Pollution sensitivity Index (CEMAGREF 1982) and the GDI - Generic Diatom Index (Coste, Ayphassorho 1991) while trophic status was estimated using TDI - Trophic Diatom Index (Kelly, Whitton 1995).

Indices determining saprobic water pollution (SPI, GDI) indicated water quality of class III and IV for the Bzura River and class II and III for the Pilica River. The trophic status determined on the basis of the TDI index revealed the Bzura water to be classified in the eutrophic-to-hypertrophic zone and that of the Pilica River to the oligo-mesotrophic-to-eutrophic zone.

The diatom taxa that dominated in the Bzura River were species that are generally considered to be tolerant and resistant with respect to organic water pollution, including: Cyclotella meneghiniana Kützing, Gomphonema parvulum (Kützing) Kützing, Nitzschia palea (Kützing) W. Smith, Nitzschia paleacea Grunow, Sellaphora pupula (Kützing) Mereschkovsky, Stephanodiscus hantzschii Grunow, Ulnaria ulna (Nitzsch) Compere. In the Pilica River diatoms from groups that are sensitive and tolerant to organic pollution were seen to dominate, such as: Achnanthidium minutissimum (Kützing) Czarnecki, Aulacoseira granulata (Ehrenberg) Simonsen, Cocconeis neodiminuta Krammer, Cocconeis placentula Ehrenberg, Cocconeis placuntula var. lineata (Ehrenberg) Grunow, Cyclotella radiosa (Grunow) Lemmermann, Fragilaria crotonensis Kitton, Geissleria decussis (Øestrup) Lange-Bertalot et Metzeltin, Melosira varians Agardh, Navicula reichardtiana Lange-Bertalot, Planothidium frequentissimum (Lange-Bertalot) Lange-Bertalot, Pseudostaurosira brevistriata (Grunow) Williams & Round, Rhoicosphenia abbreviata (Agardh) Lange-Bertalot and Staurosira pinnata Ehrenberg.

QuickBird satellite images were processed using object-based analysis to map the spatial structure of seagrass in sandy shoal habitat in the southern Baltic Sea. A three-level ecological model of seagrass landscape, composed of meadows, beds and patches/gaps, was implemented in the multi-scale object domain. Image segmentation was performed at different spatial scales. In order to determine representative scales for bed level and patch/gap level objects, histograms of delineated objects were analyzed. Using object-oriented classification methods, two hierarchically nested maps of seagrass spatial structure were created. The map of patches/gaps was created using the nearest neighbor classification method in the feature space defined by the mean value of band 2 and the value of the proposed seagrass index. Overall map accuracy was 83%. The second map, which depicted the cover density of seagrass beds, was created on the basis of hierarchical relationships between objects at two chosen spatial scale levels. Both maps were exported as vector objects to GIS. Vector-based mapping of seagrass landscape structures at two scales simultaneously provides new possibilities for using landscape metrics and time change detection methods.

The effects of abiotic environmental conditions, such as water oxygen content, pH and temperature, on the release of biogenic substances (mainly orthophosphates) from bottom sediments were examined in freshly collected samples from Lake Góreckie, Wielkopolski National Park. It was observed that their release was favoured by anaerobic conditions, alkaline pH and elevated temperatures, which are conditions naturally occurring in surface waters, especially in reservoirs of higher trophy.

Phytoseston studies were carried out at two sites near the town of Łask in the third orderstream segment of the Grabia River and the first order-stream segment of the Brodnia River, in two study periods: 1992-1993 and 2005-2006. Water and seston were sampled twice a month. The chemical parameters of N-NO₃, P-PO₄ and chlorophyll a were also determined. The aim of the studies was to determine the changes in the nutrient load of these ecosystems in the rivers studied over the course of 12 years and their influence on quantitative and qualitative phytoseston differentiation.

No important differences in the taxonomic composition of the phytoseston between the two rivers were observed. A high participation of diatoms (over 50%), in relation to other algal groups, was recorded in both rivers. Vegetation in the Brodnia River begins to develop one month earlier than in the Grabia River. The greatest changes in the seasonal rate of algal succession occurred in the spring and summer periods, while no considerable changes in seston composition were recorded in the fall or winter periods. A decrease in phytoseston quantity was observed in the second study period. Chlorophyll a content was significantly lower in 2005-2006 than that in 1992-1993.

The paper presents the application of the hydrodynamic 1D unsteady model for calculating hydro-ecological flood characteristics in the Lower Biebrza River Basin located in northeastern Poland. The 1D model is combined with the Digital Elevation Model for determining of flood extent. The model was calibrated using measurements of flood extent and verified comparing calculated flood extent to satellite images. Consequently, the flood characteristics important for plant communities of the riparian wetland were calculated for vegetation season (February-September) daily time series (1961-1996). Then, their relations to particular generalized groups of vegetation were analyzed. The results show a significant congruity between the type of vegetation and calculated flood characteristics. The hydrodynamic model was confirmed to be a useful tool for calculating flood characteristics.

Denitrification rates in the bottom sediment of the Rzeszów Reservoir (southeastern Poland) were measured using the isotope pairing technique. At the stations studied rates were reported in the range of about 26 to 610 μmol N₂ m^-2 h^-1, with the figures generally highest in summer. Simple and multiple regression analyses of relationships with selected abiotic factors gave rise to a model that revealed a statistically significant influence on rates of denitrification in the bottom sediment of the Rzeszów Reservoir due to concentrations of nitrate in overlying water, temperature, and the organic matter content in the sediment. The present study confirms that nitrate concentration in the overlying water is the main factor controlling sedimentary denitrification.

Physico-chemical variables of water quality and benthic community structure were assessed in order to evaluate the need for reinstating the use of the preliminary Jedlice Reservoir. The waters of the Mała Panew River carry a significant load of nutrient compounds, particularly nitrates and phosphates. Deteriorating water quality results in permanent algal blooms and changes in the macrofauna structure. It was confirmed that the use of a preliminary reservoir could contribute to the protection of the Turawa Dam Reservoir against pollutants transported by the waters of the Mała Panew River.

The study applied qualitative and quantitative phytoplankton analysis as a tool for determining algal community characteristics and identifying the directions and general trends of changes caused by the restoration of Lake Głęboczek through phosphorous inactivation before and during its application.

The method applied in the studied lake aimed at reducing phosphorous availability through the chemical precipitation of its excess mineral forms in the water body and limiting their mobility in the bottom sediments. Restoration efforts led to shifts in the phytoplankton domination structure followed by the inhibition of blue-green algae development. In consequence, a significant decrease was recorded in the growth rate of the phytoplankton community.

The main aim of the study was to analyze diurnal changes in the composition and dynamics of the cladoceran community among three stations located along a horizontal transect that included the central part of a Myriophyllum verticillatum bed at the perimeter of a macrophyte stand and the open water zone of neighboring vegetated stations.

Typically littoral species distinctly dominated the material examined. Ceriodaphnia quadrangula significantly influenced the total crustacean community.

The maximum abundance of littoral species was noted in the middle part of the plant stand while the minimum was in the open water. These species revealed a similar pattern of diurnal distribution, irrespective of the station, with the highest numbers at night and the lowest during the day and morning. A similar pattern of diurnal distribution was also observed for pelagic species that exhibited significant differences in the open water zone between the day (the lowest numbers) and night (the highest) samplings.

It was suggested that the diurnal distribution of cladoceran representatives between the macrophyte bed and the open water zone of Lake Wielkowiejskie might have been influenced by young fish predation (pelagic species) and by typical adaptations of particular species to living within the heterogeneous habitat of a macrophyte stand (littoral species).

The study was conducted on a degraded Lake Długie in Olsztyn (surface area 26.8 ha, max depth 17.3 m) restored in 1987 - 2000 with the method of the artificial aeration with destratification. The aim of the study was to determine the influence of the applied method on the exchange of nitrogen compounds between the bottom sediments and overlying water. The results revealed that the applied method caused a decrease of nitrogen release from the bottom sediments and influenced the content of this component in the sediments. The observed changes may have been the effect of the intensification of the coupled nitrification-denitrification processes occurring in the aquatic conditions modified by the restoration.

Marine algae in inland waters in Poland have been rarely recorded. The distribution of 5 species and 1 subspecies of the Ulva genus (syn. Enteromorpha, Chlorophyta) observed in different inland aquatic ecosystems is reported. The algal distribution was established on the basis of the available literature, unpublished material, and oral reports. Information about the algal morphology and habitat conditions, from all of the 58 reported locations of ulvas in Poland, were assimilated and are presented here.

The most widespread species of Ulva in inland waters in Poland was U. intestinalis (syn. Enteromorpha intestinalis) reported at 34 sites, while the rarest species was U. paradoxa (syn. Enteromorpha paradoxa), recorded at 2 sites.

Species of Ulva have been reported at a range of inland aquatic ecosystems, but most commonly in lakes and small water-courses, such as ditches, channels and creeks. Most of the reported sites of penetration of Ulva (Enteromorpha) inland are concentrated in northwestern and central Poland.

The use of benthic macroinvertebrates has become an important tool for monitoring the quality of freshwaters. A review is given of the development of the Biological Monitoring Working Party scheme in the United Kingdom (BMWP-UK) and how this has been modified in Poland (BMWP-PL). Methodologies are also described showing how basic data sets collected for the BMWP scheme can be used for the assessment of flow conditions and to identify sites for special conservation measures.