Search

The influence of river flow dynamics on the functioning and structure of microcrustacean assemblages (Copepoda, Cladocera, Ostracoda) in the shallow (SHz) and deep (DHz) hyporheic zone were studied in a Sava River (Slovenia) gravel bar over a 3 year period. Temperature, conductivity, dissolved oxygen concentrations, po- tential food resources (nitrates, dissolved organic carbon - DOC, particulate organic matter - POM, and electron transport system activity of biofilm - ETSA) were measured in the deep hyporheic zone (DHz, 210 - 240 cm, n = 39) on six sampling occasions (2007- 2010) and in the shallow hyporheic zone (SHz, 30 - 200 cm, n = 10) during the first two sampling dates. Microcrustaceans were collected using the Bou-Rouch pumping method. The physical and chemical properties of the deep hyporheic water, such as conductivity, pH, SO4 and POM varied significantly over time and distance from the river. Less variability was observed in ETSA. Altogether 28 microcrustacean species were recorded within the two distinct habitat types (SHz and DHz). In the latter, mainly stygobiotic species oc- curred, with Acanthocyclops venustus (Norman and T. Scott, 1906) being the most frequent and abundant. During periods of low flow, patchiness of physical and chemical properties and microcrustacean assemblages increased in comparison to periods of moderate or high flow. Similarly, the patchiness was high after severe flooding with extensive sediment movements and increased clogging of interstitial spaces by fine sediments. Fine sediments and nitrates had the strongest influence on assemblage composition. The study demonstrated a strong connection between river flow dynamics, hyporheic processes and distribution of microcrustaceans, spatially and temporally .

Spatial and temporal variation in invertebrate drift during in-stream gravel extraction in a gravel-bed river in south western Slovenia (SE Europe) was investigated. Drift samples were collected at three sites (an upstream control site and two downstream impacted sites) on the first and third days of gravel extraction. Drift measured during gravel extraction was compared to the hyporheic invertebrate community at the site of gravel extraction. Significant differences in drift were observed between the sites (ANOVA, n = 18, F = 23.29, p

Invertebrates inhabiting alpine water bodies are sensitive to environmental variability and lake faunal communities can therefore be important indicators of long-range airborne pollution, climate change and other human impacts. Information about the trophic structure and species composition of alpine lake ecosystems over space and time should therefore give important insights into environmental change effects.To explore the sensitivity of the faunal communities to environmental variability at local and regional scales we sampled biological and environmental variables from alpine lakes in seven dif- ferent alpine lake districts in six European mountain regions. The fauna of the lakes was mainly com

Ecosystem health index (EHI) and respiratory electron transport system (ETS) activity were measured in plankton and sediment communities from two Slovenian lakes differing in their trophic status. The EHIs for Lake Bled and Lake Bohinj corresponded to a health status "Middle" and "Good", respectively. The negative correlations that were found between EHI on the one hand and ETS activities of zooplankton and sediment and total ETS activity on the other indicated a higher ETS activity of zooplankton, sediment and total ETS activity at higher trophic status. The low seasonal variation of respiratory potential in the sediment, and its importance in degradation of organic matter and recycling of nutrients in the lakes, makes the measurement of the biological oxidation capacity of sediment appropriate for monitoring changes in ecosystem functioning in comparison to plankton communities. Thus, sediment ETS activity is a valuable source of information on the lake ecosystem, its functioning and its health, in combination with other indicators or information about the system. However, the interpretation of measured ETS activities of sediments needs knowledge on the specific characteristics of the lakes under investigation.

Cladocera and calanoid Copepoda are ubiquitous in surface freshwater, each with about 500-600 species and subspecies distributed worldwide. Both groups also contain some subterranean species, which occur in karst and porous aquifers. The first stygobiotic calanoid, Microdiaptomus cokeri, was described in 1942, and the first cladoceran, Alona smirnovi, in 1973. Currently, seven species of Cladocera are confirmed and three more are possible stygobionts. In Calanoida, nine species are recognized stygobionts and three more are possible. In the last few years the number of described stygobiotic taxa has increased and may continue to do so, as caves and gravel-beds are more intensively studied. Stygobionts are probably derived from a Miocene fauna that, under the constraint of a worsening climate, took advantage of the development of caves and found subterranean refugia. The Pleistocene glaciations accelerated this colonization process, which persists to the present. Both groups do not contribute much to the overall subterranean biodiversity, but they exhibit adaptations that may help to reveal the mechanisms of colonization of the subterranean realm. Some of their characteristics are related to feeding and to maintaining their position during cave floods, and are shared with other stygobionts. In addition, stygobiotic Cladocera and Calanoida have distinct life-histories and morphological adaptations. In karst-dwelling Cladocera, parthenogenesis supports fragmented populations, whereas karst-dwelling Calanoida are planktonic, a unique way of life among freshwater stygobionts.