Department of Ecology

The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates. One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores obtained from macroinvertebrate indices vary naturally between seasons, confounding the detection of anthropogenic environmental change. We investigated this problem in a 4th order calcareous stream in the western Carpathian Mountains of central Europe, the Stupavský potok brook. We divided our 100 m study site into two stretches and took two replicate samples every other month alternately from each stretch for a period of 1 year, sampling in the months of February, April, June, August, October and December. Multivariate analysis of the macroinvertebrate communities (PCA) clearly separated the samples into three groups: (1) April samples (2) June and August samples (3) October, December and February samples. Metric scores were classified into two groups those that were stable with respect to sampling month, and those that varied. Of the metrics whose values increase with amount of allochthonous organic material (ALPHA_MESO, hyporhithral, littoral, PASF, GSI new, DSI, CSI), the highest scores occurred in February, April, October and December, while for metrics whose values decrease with content of organic material (DSII, DIS, GFI D05, PORI, RETI, hypocrenal, metarhithral, RP, AKA, LITHAL, SHRED, HAI) the highest values occurred in February, April, June and December. We conclude that sampling twice a year, in early spring and late autumn, is appropriate for this type of metarhithral mountain stream. Sampling in summer is less reliable due to strong seasonal influences on many of the metrics examined while sampling in winter is inappropriate for logistical reasons.

The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates. One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores obtained from macroinvertebrate indices vary naturally between seasons, confounding the detection of anthropogenic environmental change. We investigated this problem in a 4th order calcareous stream in the western Carpathian Mountains of central Europe, the Stupavský potok brook. We divided our 100 m study site into two stretches and took two replicate samples every other month alternately from each stretch for a period of 1 year, sampling in the months of February, April, June, August, October and December. Multivariate analysis of the macroinvertebrate communities (PCA) clearly separated the samples into three groups: (1) April samples (2) June and August samples (3) October, December and February samples. Metric scores were classified into two groups those that were stable with respect to sampling month, and those that varied. Of the metrics whose values increase with amount of allochthonous organic material (ALPHA_MESO, hyporhithral, littoral, PASF, GSI new, DSI, CSI), the highest scores occurred in February, April, October and December, while for metrics whose values decrease with content of organic material (DSII, DIS, GFI D05, PORI, RETI, hypocrenal, metarhithral, RP, AKA, LITHAL, SHRED, HAI) the highest values occurred in February, April, June and December. We conclude that sampling twice a year, in early spring and late autumn, is appropriate for this type of metarhithral mountain stream. Sampling in summer is less reliable due to strong seasonal influences on many of the metrics examined while sampling in winter is inappropriate for logistical reasons.

The occurrence of preimaginal stages of Diptera (excluding Chironomidae and Simuliidae) in the Tatra Mountain lakes, their inlets and outlets, and the influence of acidification on the presence of these taxa were assessed. At 21 sites, 18 Diptera taxa were recorded in 2000 and 2001. The most frequent were Dicranota sp. (73%), Pedicia (C.)rivosa (50%) and Wiedemannia sp. (14%). Diptera were ordinated by RDA; relationships between taxa and environmental variables were significantly determined by temperature and habitat characteristics (altitude, habitat, alkalinity, Ca 2+ , pH, temperature, conductivity). The RDA diagram confirmed the existence of four Diptera assemblage groups corresponding with four habitat types. Group 1 -alpine and subalpine oligotrophic lakes at higher altitudes threatened by acidification, with the acid tolerant taxa Tipula rufina, T. alpium, Dicranota sp. and Rhypholophus sp. Group 2 -subalpine oligotrophic lakes not threatened by acidification with the acid sensitive taxa Wiedemannia sp., Hemerodromia sp., Tipula (S.)benesignata, Orimarga sp.,Chionea sp., Pedicia (C.)rivosa and Bazarella subneglecta which prefer higher temperature. Group 3 -subalpine oligotrophic lakes, with the acid sensitive speciesBerdeniella illiesi, which prefers cold water. Group 4 -outlets of submontane oligotrophic lakes with characteristic taxa Tricyphona sp. and Tipula goriziensis. Acidified alpine and subalpine Tatra lakes are situated mostly at higher altitudes (1705-2145 m a.s.l.) and have specific taxonomic composition.

Tento príspevok bol po redakčných úpravách vytlačený 18. 1. 2004 20:22:00. Číslovanie strán nezodpovedá číslovaniu, ktoré bude v konečnej podobe časopisu. Po označení potrebných opráv (štandardnými korekčnými značkami) a úpravách podľa požiadaviek redakčnej rady ho vráťte redakcii.

Thirty taxa of aquatic Diptera (excl. Chironomidae and Simuliidae) were found in the Gidra river basin in the years 1998-1999. On the basis of the occurrence of dominant and characteristic taxa 3 categories of biotopes have been specified: 1. Crenal and hypocrenal with the occurrence of crenophilous (Dixa nubilipennis Curtis, 1832, Dixa maculata c.f., Oxycera meigenii Staeger, 1844) and rhithrophilous (Liponeura cinerascens minor Bischoff, 1922, Liponeura vimmeri Mannheims, 1954, Pneumia stammeri (Jung, 1956, Pedicia (C.) straminea (Meigen, 1838)) species 2. metarhithral with high water content and characteristic taxa Ibisia marginata (Fabricius, 1781), Atherix ibis (Fabricius, 1798), Hemerodromia spp., 3. potamal with high dominance of eurytop taxon Dicranota spp. In the year 1999, less favourable from hydrological point of view, abundance, biomass and mass of an average individual in the population of species belonging to the Dicranota spp. genus were rising with rising pollution. One can assume wider availability of food consisting mainly of Tubificidae and larvae of Chironomidae increasing their abundance in organically more polluted biotopes.