Water quality and quantity significantly affects the aquatic fauna in the epikarst and conversely can also reflect the hydrological environment. Intensive, long‐term studies on hydrological and ...hydrochemical parameters were monitored at 4 permanent dripping sites (VP1–VP4) in the Velika Pasica Cave (Slovenian) over a period from 2006 to 2013 concurrently with aquatic fauna sampling. Multivariate methods were applied to elucidate the relationship between the environmental conditions and the resident aquatic ecosystem. Seven major aquatic taxa were collected from the drips, with Copepoda being the dominant taxa; however, the spatial distribution and composition of these species varied distinctively at the 4 study sites; the drip water from different sites had distinct hydrological and hydrochemical characteristics. The most significant parameters influencing community composition were drip water discharge volume and NO3− ion content. The results indicate that hydrology and hydrochemistry significantly influence the microdistribution of aquatic fauna within the epikarstic aquifer.
Groundwater invertebrate drift, collected from the spring outlets at the interface of vadose and phreatic zones, has been examined for its potential for identifying sources of discharge from a karst ...aquifer. Concurrently, major ion geochemistry, dissolved inorganic carbon (δ13CDIC), particulate organic carbon (δ13CPOC), and naturally occurring stable isotopes of oxygen and tritium (δ18O, 3H) were investigated over a period of 1 year in two outlets, a temporary (TS) and a perennial (PS) spring. A few differences in major ion geochemistry and stable isotope composition were found between the two springs together with moderate seasonal variability. In contrast, invertebrate drift showed clear differences between TS and PS springs in density and composition. Canonical correspondence analysis showed the presence of two distinct groups of samples from TS and PS, with Ca2+ as the only significant explanatory variable for differences in drift composition. Finally, certain species from the drift were found to be useful tracers for distinguishing between the phreatic and the epikarst and vadose zones as the origin of spring water.
Summary
1. Electron transport system (ETS) activity and oxygen consumption were measured in three crustacean species (Gammarus fossarum, Asellus aquaticus and Niphargus sphagnicolus) that differ in ...their pH tolerance. Measurements were made under four different pH regimes: strongly acid (pH 4.5–5.0), weakly acid (5.5–6.0), ‘neutral’ (7.0–7.8) and alkaline (8.5–9.0).
2. The significantly lower ETS activity/respiration (ETS/R) ratios observed in strongly acid water than in neutral and alkaline water indicate an effect of acidity on metabolism of the organisms. The main reason for the lower ratios is not increased oxygen consumption (except for G. fossarum in strongly acid water) but decreased ETS activity. Metabolic potential was lower in strongly and weakly acid water than in neutral water. Therefore, efficient exploitation of metabolic potential (i.e. of relatively large production of ATP with the existing enzyme machinery) probably enables N. sphagnicolus and A. aquaticus to survive in an acid environment.
3. Increased oxygen consumption of G. fossarum in strongly acid water indicates an acid stress that leads to the collapse of metabolism and, consequent death of the animals.
4. Although N. sphagnicolus is found exclusively in permanently acid water, no negative effect of alkaline water on metabolism was observed. This species can, therefore, be best considered as an acid‐resistant species, not an acidobiont.
Copepod diversity in southern European groundwater at different spatial scales was examined to evaluate the scale effect on α-, β- and γ-diversity across four regions. A total of 94 stygobiotic ...species were identified. permanova demonstrated that regional scale accounted for 47% of total variation for β-diversity. The aquifer scale was a significant component of β-diversity variation, whereas its effect on α-diversity variation was negligible. The local habitat scale accounted for 24% of total variation for α-diversity and 10% for β-diversity, respectively. Finally, mean α- and γ-diversity of aquifers were not linearly correlated, indicating a potential community saturation effect. The high level of endemism, low dispersal ability and high habitat specialization of stygobiotic copepods were invoked as major determinants of high species turnover among regions, aquifers and habitats. Scale effects on α-diversity were more controversial, suggesting that local assemblage saturation is scale-dependent and a reflection of local habitat structure and evolutionary processes.
Summary
1. Respiratory electron transport system (ETS) activity and oxygen consumption were measured at 10 °C for the hypogean amphipods Niphargus stygius (from two epikarst locations) and N. krameri ...(from a sinking river in a cave) and the epigean amphipod Gammarus fossarum (inhabiting a spring and a river).
2. ETS activity and oxygen consumption were compared between caves and the two surface locations, and between hypogean and epigean amphipods. ETS activities were found not to differ between animals from different locations, or between epigean and hypogean amphipods. As expected, the oxygen consumption of N. krameri and N. stygius was lower than that of G. fossarum.
3. The high ratio between ETS activity and oxygen consumption (ETS/R ratio) showed that N. krameri and N. stygius possess high metabolic potential that can be exploited for energy recovery and rapid restoration of body reserves immediately following the appearance of favourable conditions (food and/or oxygen). In contrast, G. fossarum exhibited a low ETS/R ratio, indicating exploitation of a great proportion of the metabolic potential for standard metabolism.
4. Feeding in N. stygius increased oxygen consumption but not ETS activity, and thus fed N. stygius had a much lower ETS/R ratio than starved ones.
5. A relatively high metabolic potential (i.e. high ETS/R ratio) may be an adaptation to hypogean life in amphipods, in that it improves survival under poor food and/or oxygen conditions.
In order to reveal the temperature variation mechanism of a small and relatively closed cave, the surface temperature, the cave air temperature and the drip water temperatures were monitored with ...high-resolution recorders for a 7-year period. The results indicated that the cave temperature is mainly affected by the external seasonal oscillations. The temperature curve of the inner cave area (with standard deviation between 0.59 and 0.87) was much smoother in comparison with that of the surface (with SD as high as 8.46). However, the cave reacted to the temperature drifts with some delay, for example, at VP3 in 2006, the internal temperature increased for additional 49 days after the surface temperature dropped colder than inside of the cave. This seasonal variation and delayed response of the internal temperature were mainly affected by conduction from the epikarst rock mass. Air convection also occurred in the cave, especially when the surface temperature dropped lower than that of the inside cave (during the winter time) and in the outer section (close to the entrance), which caused an abrupt and irregular variation of the outer section. In addition, the influence from the percolating water was ephemeral and depended on its supplementary amount and temperature difference, e.g., there were more apparent responses at VP1 and VP3 when the intensive rain fell. The percolating water temperature could be a good indicator for water flow in epikarst.
Summary
1. Use of electron transport system (ETS) activity in a single leg for estimating whole‐body ETS activity was explored in the noble crayfish Astacus astacus. Oxygen consumption and ETS ...activity of the whole body and of a walking leg were measured in different‐sized animals at 10 °C to compare the size scaling of oxygen consumption, whole‐body ETS activity and the ratio of whole‐body ETS activity to oxygen consumption (ETS/R).
2. Electron transport system activity of a leg and the ratio of ETS activity of a whole crayfish to that of a leg were correlated with wet mass of animals. Therefore, metabolic potential in whole noble crayfish can be estimated on the basis of the measured ETS activity in a single leg and crayfish mass. This approach provides a valuable tool for determining metabolic characteristics of crayfish without killing them.
3. Mass‐specific oxygen consumption decreased with increasing wet mass, while ETS activity of whole crayfish showed no significant correlation with wet mass. Both oxygen consumption and ETS activity correlated significantly with protein mass.
4. The increase in ETS/R with increasing wet mass of the noble crayfish indicates that small organisms exploit a greater proportion of their metabolic potential for standard metabolism than larger ones. This is the first report on ETS/R in crayfish.
A series of sampling sites in 6 caves was established in order to assess the importance of the epikarst as a habitat of high diversity of meiofauna. Special attention was given to the stygobiotic ...species of copepods (Crustacea), which was the most abundant group of animals in water percolating from the epikarst. In total, 37 species of Copepoda were identified from nearly 4000 individuals. To understand epikarst as a habitat, 14 structural and physico-chemical factors were analysed and compared for two types of habitats, i.e., trickles and pools filled with percolation water. Results of canonical correspondence analysis indicated that the significant factors influencing faunal composition in trickles were the thickness of the cave ceiling and the concentrations of sodium, nitrate, and potassium ions, while in pools correlations between individual species and pH, temperature, volume, conductivity and thickness of the cave ceiling were statistically significant. Aquatic copepod assemblages in epikarst encompass species of different taxonomic affinities, living in severe environmental conditions. The pattern of the system reflects both high taxonomic diversity and environmental severity.PUBLICATION ABSTRACT
Interstitial water that occupies the pore spaces within unconsolidated sediments is a unique habitat, inhabited by surface as well as exclusively subterranean species (stygobionts). The best studied ...of all interstitial habitats is the hyporheic zone, an interface between surface water and groundwater (phreatic zone) environments. The Sava River in central Slovenia (i.e., at the Ljubljana alluvial plain) readily qualifies as one of the global hotspots of interstitial biodiversity, while data from other river sections are lacking. In 2015, we sampled two gravel bars on the final Slovenian section of the river (Eastern Slovenia), and collected nine samples per site using the Bou-Rouch pumping method. At »Čatež ob Savi« and »Obrežje« sites, at least 26 invertebrate species with 14 stygobionts and 25 invertebrate species with 13 stygobionts were identified, respectively. Altogether, 33 invertebrate taxa with 16 stygobionts were recorded, which increased the previously known interstitial stygobiotic richness of the Sava River in Slovenia by eight species (to 37 species). Three species of the stygobiotic amphipod genus Niphargus were recorded in Slovenia for the first time, one of which is even a new species to science. We discuss the novel results in the context of current national conservation practices.
Slovenia (southeastern Europe, area 20000 km^sup 2^) and neighbouring northeastern Italy (Venezia-Giulia) are rich with endemic taxa of Copepoda, most of them stygobionts. Untill now, only one could ...be considered as an epigean, rheophilic endemic taxon. In 1986 and 1987, several females were collected from the mountain Radovna River in northwestern Slovenia. They were recognised as new subspecies and described as Moraria pectinata radovnaeBrancelj, 1988. Ten years later, three males and two females were found in a small mountain brook in northeastern Slovenia (about 100 km from loc. typ.) in different geology. This gave an opportunity to raise the taxon to the specific level. The male of M. radovnae differs clearly from M. pectinata Thiébaud & Pelosse, 1928; also it is evident that both taxa are closely related. A detailed description of the male of M. radovnae Brancelj, 1988 is given. Based on data from the literature and reports, 14 endemic taxa are found exclusively in Slovenia, and an additional 5 taxa have their type localities (loc. typ.) there. Several more taxa were described, but later they were synonymised. Five endemic taxa, namely Diacyclops hypogeus (Kiefer, 1930), Nitocrella slovenica Petkovski, 1959, Elaphoidella franciPetkovski 1983, E. kieferi Petkovski & Brancelj, 1985, and Paracamptus gasparoiStoch, 1998, were reported only once. Three endemics were found on several occasions at the same location, and six taxa were found in more than one location within Slovenia. Of these, only Elaphoidella stammeriChappuis, 1936, could be considered as a common endemic species. Most of the endemics were found exclusively in percolating water in caves. The five taxa with loc. typ. in Slovenia are known in some areas of neighbouring countries, namely Italy and Croatia.PUBLICATION ABSTRACT
