Volume 36 (2007): Issue 3 (September 2007)

The diatom records of two sediment cores taken in the SW part of the Gulf of Gdańsk indicate paleoenvironmental variability in the last three stages of formation of the Baltic Sea: the Mastogloia, the Littorina and the Post-Littorina. Diatom community compositions of the cores show the influence of several factors on past environmental conditions of the study area: (1) regional salinity changes, (2) changes of the Vistula River inflow, and (3) sedimentary processes connected with the Hel Peninsula development.

Research on the swan mussel population was conducted in 2005 on a sample of 497 individuals inhabiting Binowo and Bobolin Lakes, Szczecin, Poland. Length, width, height and age of individuals was examined. Binowo Lake was inhabited by individuals aged 1+ to 7+ years, while individuals aged 1+ to 6+ inhabit Bobolin Lake. Measurable features of swan mussels inhabiting Binowo Lake were as follows: individuals were 3.80 to 10.20 cm long, 1.70 to 5.70 cm wide, 0.70 to 3.70 cm thick, and in Bobolin Lake, 4.00 to 15.20 cm long, 2.20 to 7.70 cm wide, 0.80 to 5.70 cm thick. The age structure of both populations included individuals of diverse ages, with 3 and 4-year old individuals dominating in both lakes. A modest fraction of the youngest individuals (1, 2-year old) as well as the oldest (6, 7-year old) was observed in the examined lakes. All correlations between shell length, width, height and mussel age showed large positive correlations and results obtained from both lakes were similar.

The structure of the zooplankton community and its spatial distribution were examined in two stratified rheolimnic Pomeranian reservoirs, Rosnowski (7 sampling sites) and Hajka (4 sampling sites), in July 1999. These reservoirs are part of the cascade system situated on the Radew River in northern Poland. In the Rosnowski reservoir 34 species of zooplankton were identified and in Hajka, 32. The two dominant species of rotifers in both reservoirs were Keratella cochlearis f. tecta and Polyarthra vulgaris. The dominant copepod and cladoceran species in both reservoirs were Mesocyclops leuckarti and Daphnia cucullata, respectively. Along the longitudinal axis of both reservoirs, rotifers were the dominant group at all sampling sites, except for the hypolimnion layer in both reservoirs and the metalimnion layer in Hajka reservoir at site H1. This initial study was undertaken in order to determine the spatial distribution of rotifer, copepod and cladoceran communities in riverine reservoirs built in the cascade system.

Phytoplankton species composition, abundance and biomass were studied in samples taken from the epilimnion of Lake Strzeszyńskie in late August of each year from 2000-2005. The number of phytoplankton species was relatively low, with the greatest species diversity observed in the Chlorophyceae. Total phytoplankton abundance was high, with major contributions by picophytoplanktonic cyanobacteria, which formed aggregations. Total phytoplankton biomass was generally low, with the sum of the 2-5 biomass-dominant species always exceeding 50% of the total phytoplankton biomass. The taxonomic composition of the group of biomass dominants was relatively stable inter-annually. On the basis of phytoplankton biomass and chlorophyll a concentration, Lake Strzeszyńskie can be classified as oligo-mesotrophic and mesotrophic, respectively. Trophic index values calculated on the basis of abundance of phytoplankton indicator taxa were higher than the values based on their biomass, and mean values indicate that the lake is mesotrophic or intermediate between mesotrophic and eutrophic.

The aim of this study was to examine levels of persistent organic pollutants (POPs) in cod from the Barents Sea. Samples were collected in two regions, the warm waters of the West Spitsbergen Current, where surface temperatures are typically 3.5-6.5°C, and the cold waters of the East Spitsbergen Current, where the surface temperature is generally -1.5-1.5°C.

The concentrations of selected POPs were analysed in muscle and liver tissues of cod. The observed POPs content were lower than in comparable samples from urban regions. Significant differences were seen between the POPs contents in samples of cod from the two regions. These differences can be attributed to the distinct characteristics of the two water bodies, the West and East Spitsbergen Currents.

The Vistula is the second largest river in the Baltic Sea catchment area and provides one of the main inputs to the Baltic. The river and its tributaries flow through some of the major industrialized and urbanised regions of Poland, making it one of the most highly human-impacted rivers in Europe. Although the river status is monitored routinely, little is known about mercury forms in the sediments. This study examines mercury fractionation in the sediments of the lower part of the Vistula River. The results show that the cities along this stretch of river have a relatively low impact on both the mercury forms found in the sediment and its bioavailability in the floodplain soils. The mean concentration of total mercury in the sediments was 65 ± 14 ng g^-1 dry mass (range 54-92), calculated as the sum of mercury concentrations in the individual fractions. The most abundantly represented of these fractions were mercury bound to sulphides (68 ± 11%, range 55-82%) and humic matter (19 ± 10%, range 10-35%), with lower fractions of water-soluble mercury (6.9 ± 2.9%, range 5.1-13%) and organomercury compounds (6.4 ± 5.3%, range 0.6-13%). The least abundant fraction observed was acid-soluble mercury (0.3 ± 0.2%, range 0.1-0.6%). Similar concentrations and fractionation were observed in floodplain soils from Kiezmark, collected 1, 10 and 50 meters from the riverbed.

Microbiological analysis of shrimp exoskeletons demonstrated considerable differences in abundance of heterotrophic bacteria and fungi. The number of heterotrophic bacteria was greater by two orders of magnitude than that of fungi. The survey, however, did not reveal significant differences in abundances of bacteria and fungi in samples collected during different months of the survey. The percent contribution of chitinolytic fungi in shrimp exoskeletons was greater than that of bacteria that hydrolyze chitin. The activity of chitinase bacteria was always higher than fungi. Chitinases produced by bacteria demonstrated the highest level of activity at 40°C and pH = 8. In contrast, fungal chitinases showed the highest activity at 50°C and pH = 5.

Estuaries are considered adverse environments for many living organisms because of their unstable environmental conditions. Variability in salinity, temperature and oxygen concentration of the water, diverse substrata and geomorphological structures are major contributors to increased ecological stress in estuaries. These variations contribute to the characteristic estuarine spatial and temporal changes of physico-chemical properties, which operate even at small scales.

In terms of biology estuaries represent fascinating environments — transition zones between freshwater and marine biomes. Freshwater entering an estuary has a major influence on the ecology of the system, its productivity, diversity and the distribution of organisms, with a high variability of niches favouring an increase of biodiversity and biomass. Many estuarine species/organisms show broad and efficient physiological adaptations (ecotypes) in response to these environmental factors. Under locally specific conditions, even different genetic clades (groups) can be formed. Estuaries serve as vital nursery systems for many fish and unique feeding grounds for migratory birds. On the other hand, estuaries are often seriously degraded habitats, hence providing an ideal environment for combining studies on ecology, nature conservation and human impact.