An analysis of the species composition of zooplankton of Lake Gardno was based on the materials collected in the years 1998–2002, from July to August. It was found that the numbers of zooplankton species, their abundance and biomass were greatly variable, and depended on abiotic factors and lake trophy. An analysis of the structural characteristics of zooplankton as bioindicators of lake eutrophication revealed the presence of some species of rotifers and crustaceans in the zooplankton community, considered good indicators of lake trophy. The zooplankton-related trophic state indices enabled to classify Lake Gardno as eutrophic and meso-eutrophic.
Alien species are now found all over the world. New fish parasites have been unintentionally introduced with infected alien fish imported for aquaculture or have sometimes spread with their intermediate invertebrate hosts transported in the ballast waters of ships. Four alien fish parasites have been recorded in Polish coastal lakes and lagoons, all parasitising eels. Three were introduced with the final host – the Japanese eel – introduced for aquaculture (Anguillicola crassus, Pseudodactylogyrus anguillae and Pseudodactylogyrus bini) and one (Paratenuisentis ambiguus) with its sole intermediate host (Gammarus tigrinus).
An account is given of the occurrence of Pediastrum (Chlorophyceae, Sphaeropleales) in five eutrophic coastal lakes (Jamno, Bukowo, Gardno, Łebsko and Sarbsko) in northern Poland, together with morphological data of the species and more detailed taxonomic and ecological information for three taxa which appear to be rare world wide. These are P. musterii, P. orientale and P. alternans; the first is recorded for the first time from central Europe. P. orientale and P. alternans show considerable morphological variability under different environmental conditions, indicating the need for further studies. The studied lakes seem to be especially favourable for Pediastrum, with a total of eight species (15 taxa) in the phytoplankton noted during the summer. However, the relative frequency of the genus in the overall algal communities was low. The most frequent species were P. boryanum, P. kawraiskyi and P. duplex and these were accompanied by cyanobacteria, coccal green algae (Chlorophyceae, Chlorococcales) and diatoms (Bacillariophyceae). All the Pediastrum taxa were documented using LM and SEM.
The paper presents the results of the study of abundance, production and respiration in surface layers and subsurface water in the coastal lake Dołgie Wielkie. Indicate that the total numbers of neustonic bacteria were higher than planktonic bacteria. The level of production and respiration rate were higher in the subsurface water than in surface layers. Bacterial abundance, production and respiration rate were changing with seasons.
The paper presents the analysis of thermal conditions of coastal Lake Jamno. The long observation series (1971-2013) for the course of surface water temperature suggests its considerable warming (0.28°C∙dec-1). In the monthly cycle, an increase in surface water temperature is observed in all cases except for the winter period (December, January, February). Water was heated the fastest in April (0.58°C∙dec-1) as well as May and September (0.46°C∙dec-1). Mean annual air temperature increased at a similar rate (0.27°C∙dec-1), but the coefficient of correlation of both media equalled 0.40. This suggests that other factors could contribute to the change in surface water temperature. One of such factors could be marine water intrusions. The strongest positive correlations of water temperature in Jamno and water level in the Baltic Sea occurred in the cold half-year, and negative in the warm half-year. From 2013, on the canal connecting Lake Jamno with the Baltic Sea, a storm gate was constructed that altered many processes and phenomena occurring in the lake so far. The paper covers the natural (quasi-natural) period of functioning of the lake, and provides a point of reference for future research on its thermal regime considering among others the effect of human pressure in the form of hydrotechnical infrastructure.
The paper presents studies on level hydrolytic activity of extracellular enzymes in the surface microlayer and subsurface water in the coastal lake Dołgie Wielkie. The ranking order of the potential enzyme activity rates in the studied water layers was as follows: aminopeptidase > lipase > α-glucosidase > β-glucosidase. The level of activity of all studied hydrolases was higher in the surface microlayer than subsurface water. Activity of extracellular enzymes was influenced by the season.