Population of the freshwater amphipod Gammarus fossarum was investigated in a calcareous stream with almost constant temperature (7-8• C) in the Chočské Vrchy Mts (West Carpathians, Slovakia). Quantitative samples of G. fossarum taken during 2005 showed population densities varying from 100 m −2 in August to 585 m −2 in late November. The population was split into juveniles, mature males, mature females without eggs and females with eggs. The percentage of juveniles (40-64%) was always the highest of any of the categories. Ovigerous females occurred throughout the year. The mean sex ratio was 1 : 2.4 (male: female), although its values varied considerably with the time of year. Breeding was continuous, although juvenile recruitment peaked in early spring, summer and early winter. Three discrete cohorts were distinguished from the size frequency distributions. The life span was 6-7 months and the individuals matured approximately in the half of life cycle. The mean fecundity was 9.6 embryos per brood. Variation in fecundity was mostly explained by size of the incubating females. The absolute growth of this species was best described by the Gompertz growth function. Relative growth rates (% body DM day −1 ) fluctuated in a nonlinear manner with size and age. The highest values of daily growth (2-4% of dry mass per day) were noted approximately in the half of life cycle. Annual production, estimated by the size-frequency method, was 1618.9 g dry mass m −2 and P/B ratio was 5.15.

No abstract

A method is presented for defining the five classes of ecological quality based on a multimetric index (MMI) of macroinvertebrates, as required for implementation of the Water Framework Directive for small (catchment area 10-100 km 2 ), medium (101-1000 km 2 ) and large (> 1000 km 2 ) streams. Our method (expert judgment) allows us to overcome an absence of reference sites for some stream types. The key was selection of suitable metrics for all stream types. The whole procedure was divided into two parts. 1. Small streams with reference sites: suitable metrics were selected according to their ability to distinguish reference and monitoring sites -SI, Oligo [%], BMWP, RhiTI, Rheoindex, IBCR, % Aka+Lit+Psa [%] and EPT. Here the high-good boundary value was set as the 25 th (for metrics decreasing with increasing pollution) or 75 th percentile (for metrics increasing with increasing pollution). 2. Medium and large streams which lack reference sites: here the idea was applied that some metrics, the values of which change along an altitudinal gradient, also react to anthropogenic stress -SI, Oligo [%], BMWP, [%] metarhithral, RhiTI, Aka+Lit+Psa [%] and EPT for both medium and large streams with, in addition, IBCR and NFam for medium streams. This assumption was supported by regression analysis of altitude and metrics from small streams. Not all the metrics were related to altitude but metrics with a good ability to separate reference and monitoring sites did show a significant relationship to altitude. The boundary between high and good class for medium and large streams was set as the 95 th or 5 th percentiles.Key words: ecological quality ratio; reference status; streams; benthic invertebrates; multimetric index; Slovakia

The nymphal biology (life cycle, secondary production and feeding) of a population of Protonemura intricata was studied in a calcareous stream with almost constant temperature (7-8 °C) through the year at Prosiek valley (Chočské Vrchy Mts., West Carpathians, Slovakia). The results were compared with those previously known for this species in other areas. According to our data, the species has a complicated life cycle consisting of two cohorts with different duration (probably a cohort splitting). This life cycle seems to be uncommon among the Plecoptera, which usually has simple univoltine or semivoltine life cycles, and could be probably attributed to the constant temperature regime similar to that of tropical environments. One factor, the photoperiod length, was positively correlated with monthly growth rates. The nymphal growth varied throughout the year, but the highest growth was in late spring and summer, and the lowest was in winter. The annual secondary production was very high (909.4 mg · m -2 ) despite not being the most frequent taxon in the stream. The highest monthly production values were observed in the autumnal-winter period (November-December) due to massive hatching of nymphs. The lowest production values were observed in late summer and early autumn. Analyses of gut contents showed that this species behaves mainly as gatherer-collector, but also as shredder and, occasionally, as scraper. Changes in the gut content composition were detected in relation to the size. Comparing our results with those of the literature, it can be inferred that different populations of P. intricata can show notable differences in their life history when inhabiting places with different thermal conditions. IntroductionOne of the most important aspects for understanding freshwater ecosystems is the biology of the species that live in them. In this context, the study of the life history of single species is essential in order to achieve a full knowledge of the ecosystem itself and the relations within it. Many studies have tried to reach this goal through generalizations taken from the study of a reduced number of species, assuming that the rest of the members of their genus or family behave in the same manner. As pointed out by several authors (ZWICK, 1981;STEWART and STARK, 1993), this is neither a good approximation nor an appropriate * Corresponding author 58 Z. KOZÁČEKOVÁ et al.

Abstract:The effects of land use on black fly assemblages were investigated in submontane rivers (the Ľubochnianka River, the Revúca River, upper Váh River catchment) in the Carpathians. We recorded 11 black fly species in the Ľubochnianka River and 10 species in the Revúca River. Land use differs between the catchments; the Ľubochnianka is a primarily forested catchment, and the Revúca is markedly deforested catchment. Fifteen environmental variables were analysed. Based on the results provided by CANOCO, phosphorus level and stream slope are the most important variables and have significant influences on the variability of black fly assemblages. In spring, Prosimulium rufipes occurred along the entire lengths of the streams. The black fly assemblage of the Revúca River differs from the assemblage of the Ľubochnianka River mainly by its higher abundances of Simulium variegatum and Simulium ornatum, by the presence of Simulium carthusiense, and by the absence of Prosimulium hirtipes.

Changes in land use practices have affected the integrity and the quality of stream water worldwide. Effective catchment management, in terms of land use alteration, depends on our ability to quantify ecologically significant changes and to discriminate among varying levels of impact. In this study, we assessed the structural and functional changes upstream and downstream of eight small water reservoirs in western Slovakia and the relationship between these changes and shifts in physicochemical parameters as a consequence of stream damming and catchment land use. Dams were categorized into two groups, the first with both inlet and outlet situated in deforested and agricultural landscape and the second with inlet flowing through natural and forested landscape, while outlet is situated in deforested and urban region. Using a "between-groups" principal components analysis and a "between-groups" fuzzy principal components analysis, we found significant differences in structural and functional composition of macroinvertebrate communities between inlets with forested catchment and outlets flowing through agricultural, urban landscape. The structural dissimilarity is best explained by the physicochemical and biological characteristics of the aquatic environment, while functional variation of communities is best explained by land use of an area surrounding the stream. The distance in structural and functional community composition between inlet and outlet was linked with difference in environmental conditions between these habitats. The change of structural community composition significantly reflected shift in the water temperature and phosphorus concentration, while the change of functional community composition was determined by change of nutrient concentrations (e.g., PO4, NO3, NH4) and pH.

This study was based on the complex environmental monitoring of the Danube River in Slovakia. Out of 23 monitored sites, three were chosen for the aim of this study. The three sites were sampled regularly three times per year during a 25-year period, which started in 1990, 2 years before the Gabčíkovo waterworks became operational. Each site represented one of the main potamal types, which we recognised according to the habitat characteristics as eupotamal, parapotamal and plesiopotamal. In order to assess changes which occurred during the 25 years, we studied taxocoenoses of Ephemeroptera, Plecoptera and Trichoptera, which sensitively reflect anthropogenic impacts. The changes caused by the Gabčíkovo waterworks manifested in a decrease of the species diversity in eupotamal because of the disappearance of rheophilous taxa. In the parapotamal and plesiopotamal sites, the initial decrease was followed by a partial recovery of biodiversity due to the artificial floodings. After they were stopped, the decrease occurred again and until 2015, the insect taxa became rare. Conversely, in the eupotamal site, there was an increasing trend in biodiversity since 2011 until 2015. Overall increase in the floodplain index values indicated a loss of connectivity between the floodplain habitats and their fauna with the main channel during the last 25 years. In this paper, we also extended the floodplain index with data on habitat values and indication weight for several stonefly species.

The leech Dina punctata JOHANSON, 1927 inhabits various types of running waters. This species appeared in Slovakia probably after the first Rhine-Main-Danube canal was built. Because little is known about its ecology, the aim of our study was to analyze the life cycle, individual growth rate, reproduction parameters and food composition of D. punctata in the Vydrica Stream. Samples of leeches were taken mainly each month from April 2003 to November 2004. The leech D. punctata had maximal 2-year life cycle there. Mature leeches, which were recognized by the presence of clitella, were present from April to the end of August. The most individuals mature at the age of 1 year. The breeding season of D. punctata peaks in June. The number of eggs per one cocoon is from 3 to 12. The mean successfulness of development of egg to embryo is 58%. Larvae from the family Chironomidae (28%), Gammarus fossarum (20%) and oligochaetes from the subfamily Naidinae (17%) are the dominant components of the feeding niche.