Pavel Beracko

Life history, secondary production and population dynamics of Gammarus fossarum (Koch, 1836) in a constant temperature stream

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.

Assessment of running waters (Slovakia) using benthic macroinvertebrates — derivation of ecological quality classes with respect to altitudinal gradients

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 km2), medium (101–1000 km2) and large (> 1000 km2) 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 25th (for metrics decreasing with increasing pollution) or 75th 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 95th or 5th percentiles.

Effects of land use on black fly assemblages (Diptera: Simuliidae) in submontane rivers (West Carpathians, Slovakia)

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.

Blackfly (Diptera, Simuliidae) communities and species richness estimation in Carpathian montane streams

The present work gives the result of blackfly fauna research of the Slovenský raj (West Carpathians, Slovakia). Our aim was to describe the composition of blackfly communities, find indicator species for communities, describe environmental factors affecting communities and determine the potential changes in species richness. Research was carried out in 2007 and 2008. The presence of 22 species of blackflies was confirmed at 20 sites in the area of Slovenský raj. 12 species were recorded for the first time in this area. The potential for further increase in diversity was calculated by a nonparametric estimation of species richness. Two main groups of sites with their typical blackflies communities were indentified using a TWINSPAN analysis. The presence of Simulium ornatum, S. variegatum and S. argyreatum was typical in larger streams in broad valleys. The absence or low abundance of these species was typical for smaller streams in canyons. Based on the species composition of blackflies communities, we identified 6 groups of sites: 1. anthropogenically disturbed submountain rivers (typical species: Simuliumornatum, S. reptans, S. equinum), 2. undisturbed metarhithral (typical species: Simulium bertrandi, S. codreanui, S. costatum, S. vernum, S. argenteostriatum, S. degrangei, S. argyreatum, S. variegatum), 3. undisturbed hyporhithral (typical species: Simuliumtrifasciatum, S. tuberosum), 4. undisturbed epirhithral (typical species: Prosimulium hirtipes, P. rufipes), 5. hypocrenal (typical species: Simulium cryophilum, S. monticola) and 6. anthropogenically disturbed epirhithral (typical species: Simulium brevidens, S. maximum). The most important environmental factors explaining differences in species composition like altitude, flow speed, pH, conductivity, oxygen saturation, sulphates concentration and presence of riparian vegetation were identified by the CCA analysis.

Downstream effect of a pumped-storage hydropower plant on river habitat conditions and benthic life – a case study

Abstract In spite of many investigations about the impact of reservoirs on river continuum, the downstream effects of a pumped-storage hydropower plants (PSHP) still have been less known. The aim of the study was to evaluate the downstream effect of the PSHP Čierny Váh in regard to the Serial Discontinuity Concept assumptions or studies assessing more frequent types of hydropower reservoirs. We predicted that the increase of water temperature and the alteration of food sources will hierarchically be the most relevant factors determining macroinvertebrate community composition. We focused on mayflies, caddisflies and non-insect benthic invertebrates due to their appropriate responses to discontinuity. We also determined the influence of the hydropower plant on life cycles and productions of the most abundant species of mayflies and caddisflies. We recorded the unique effect of the PSHP Čierny Váh on its downstream environmental variables. According to the nested ANOVA results, temperature regime, transported organic matter, benthic fine particulate organic matter and periphyton biomass were the environmental variables significantly modified by the river discontinuum. Significant differences were also found in the case of macroinvertebrate species richness, density and diversity. Nevertheless, based on the forward selection test for predictor effects, none of the environmental variables affected the macroinvertebrate assemblages significantly. However, the redundancy analysis revealed a separated group of macroinvertebrates preferring conditions characteristic for the site immediately below the reservoir. Regarding the impact of the reservoir on life histories, we revealed the shift in hatching, emergence and duration of life cycles of the abundant mayflies (except Baetis rhodani) and caddisfly Ecclisopteryx dalecarlica. Total annual production of mayflies as well as caddisflies was several times higher at the site immediately below the reservoir. Although PSHP Čierny Váh matches the SDC assumptions (except thermal stratification), the downstream impact resembles much more the effects of small reservoirs or epilimnetic-release reservoirs.

Bioassessment of streams based on macroinvertebrates — can sampling of some substrate types be excluded?

Abstract Attempting to help reduce the costs of bioassessment of aquatic habitats, the aim of this study was to estimate how particular substrate types influence the ecological quality evaluation based on a multihabitat scheme proposed by the AQEM/STAR consortium. Samples of macroinvertebrates were taken from the Stupavský potok brook, a small, 4th order calcareous stream in the Small Carpathians in Slovakia (Central Europe). Eight most suitable metrics for small Slovakian streams forming the Slovak multimetric index on seven substrate types were tested and compared with the multihabitat sample. The Saprobic Index (SI) and Index of Biocenotic Region (IBR) showed considerably worse (higher) values in the psammal and the best (lowest) values on coarse mineral substrates (lithal, akal). Similarly, values of the metrics Oligo (%), BMWP Score, Rheoindex, Rhithron Typie Index (%) and EPT reached their worst (lowest) values on psammal and the best (highest) values on coarse mineral substrates. Psammal sample showed the worst ecological quality expressed by the lowest EQR (Ecological Quality Ratio) value, most significantly differing from the multihabitat sample (Multiple Comparisons of Means: Dunnett Contrasts: –8.25, P < 0.01). We conclude that substrate types considerably influence selected metrics. Because of a relatively substantial proportion of psammal in some small Slovakian streams and its marginal influence on the overall ecological quality of the site, we suggest conduct further research addressing the effectiveness of its usage in the water management.

Influence of land use on hyporheos in catchment streams of the Velka Fatra Mts

The historical influence of landscape on the quantitative variables and a special group of hyporheos in streams with similar origin but different catchment landscapes and forest management was studied. The study was conducted in two streams: (i) a preserved forested natural stream where critical ecosystem processes were unaltered by human activities and (ii) a stream with the strong anthropogenic stressors (e.g., logging, agriculture, pasture), impacting the system for the last 500 years. Some parameters were strongly related to these land use: conductivity, fine benthic organic matter (FBOM), orthophosphate (P_PO4) and periphyton content all increased along the gradient from the natural stream to the urban-dominated catchment. The density of interstitial assemblages corresponded with the conductivity (at P < 0.05) and was higher on the stream in urban-dominated catchments; and the Harpacticoida taxa richness, dominated by the family Canthocamptidae, was also greater here. The Multiple Regression Analysis shows that the rate of deforestation had had the most significant effect on the density of hyporheos. Among of crustacean fauna the representatives of epigean harpacticoids from (of) family Canthocamptidae, dominated.