Benthic and Hyporheic Macroinvertebrate Distribution Within the Heads and Tails of Riffles During Baseflow Conditions

The distribution of lotic fauna is widely acknowledged to be patchy reflecting the interaction between biotic and abiotic factors. In an in-situ field study, the distribution of benthic and hyporheic invertebrates in the heads (downwelling) and tails (upwelling) of riffles were examined during stable baseflow conditions. Riffle heads were found to contain a greater proportion of interstitial fine sediment than riffle tails. Significant differences in the composition of benthic communities were associated with the amount of fine sediment. Riffle tail habitats supported a greater abundance and diversity of invertebrates sensitive to fine sediment such as EPT taxa. Shredder feeding taxa were more abundant in riffle heads suggesting greater availability of organic matter. In contrast, no significant differences in the hyporheic community were recorded between riffle heads and tails. We hypothesise that clogging of hyporheic interstices with fine sediments may have resulted in the homogenization of the invertebrate community by limiting faunal movement into the hyporheic zone at both the riffle head and tail. The results suggest that vertical hydrological exchange significantly influences the distribution of fine sediment and macroinvertebrate communities at the riffle scale

Biological and trophic consequences of genetic introgression between endemic and invasive Barbus fishes.

Genetic introgression with native species is recognized as a detrimental impact resulting from biological invasions involving taxonomically similar invaders. Whilst the underlying genetic mechanisms are increasingly understood, the ecological consequences of introgression are relatively less studied, despite their utility for increasing knowledge on how invasion impacts can manifest. Here, the ecological consequences of genetic introgression from an invasive congener were tested using the endemic barbel populations of central Italy, where the invader was the European barbel Barbus barbus. Four populations of native Barbus species (B. plebejus and B. tyberinus) were studied: two purebred and two completely introgressed with alien B. barbus. Across the four populations, differences in their biological traits (growth, body condition and population demographic structure) and trophic ecology (gut content analysis and stable isotope analysis) were tested. While all populations had similar body condition and were dominated by fish up to 2 years of age, the introgressed fish had substantially greater lengths at the same age, with maximum lengths 410-460 mm in hybrids versus 340-360 mm in native purebred barbel. The population characterized by the highest number of introgressed B. barbus alleles (81 %) had the largest trophic niche and a substantially lower trophic position than the other populations through its exploitation of a wider range of resources (e.g. small fishes and plants). These results attest that the genetic introgression of an invasive congener with native species can result in substantial ecological consequences, including the potential for cascading effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s10530-021-02577-6

The ecological requirements of caddisflies larvae (Insecta: Trichoptera) and their usefulness in water quality assessment of a river in south-west Romania

This survey analyzed the eco-physiological requirements of caddisflies assemblages in Jiu River (south- west Romania). The output revealed that the communities are driven by a synergic combination of natural factors and pollutants. Their ecological profiles are diverse and the degree of tolerance is related to a decrease of water quality over a longitudinal gradient, overlapped with natural variation of physic-chemical factors. The assemblage is dominated by hydropsychids, very tolerant to anthropogenic disturbances, and two other communities separated by large distances (characteristic of headwaters and of lowland areas, respectively) that do rather reveal stronger affinities to the microhabitat requirements then to water pollution. Polyhedral diagrams were employed in order to reveal caddisflies larvae tolerances/intolerances to environmental parameters, in order to test their usefulness for local areas and less numerous samples, as frequently encountered in routine surveys

The assessment of the habitat and water quality requirements of the stone crayfish ( Austropotamobius torrentium

The species Austropotamobius torrentium and Astacus astacus are two species known in the EU directives to require deeper understanding of their autecologic requirements before any sustainable conservation effort could be successfully applied. Therefore, the paper aims to analyze the occurrence of these two species of crayfish in the Anina Mountains (Romania) in relation to several physical-chemical indicators measured on site. The results suggest that the anthropogenic impacts registered in some of the sampling sites (e.g. organic pollution and river bed modification) might have triggered the disappearance of both species from the areas of the water sheds situated downstream villages and towns, deforestation sites and sewage treatment plants. The analysis suggest that both species might have similar ecologic requirements, with a BMWP score of 8 (out of a possible 10), therefore good indicators of pristine aquatic environments and with a possible toleration to pollution but only up to a moderate level. Nevertheless, the lack of cohabitation of the populations of both species at a local scale was discussed along with two possible explaining hypotheses: behavioral exclusion or different times and/or modalities of dispersal history

Stygobitic invertebrates in groundwater : a review from a hydrogeological perspective

Groundwater-adapted species (known as stygobites) provide an important contribution to biodiversity. Groundwater ecosystems are some of the oldest on earth, and contain many endemic species adapted to live in an environment with no light and limited resources. The controls on stygobite distributions are not yet fully resolved because of the complex interaction between many processes operating at different scales. Many of these processes are geological or hydrogeological in nature and therefore more detailed geological and hydrogeological studies could provide improved understanding of stygobite distributions. Hydrogeologists can assist ecologists by providing expertise on both general geological characteristics of sampling sites, and how groundwater at sampling sites relates to the wider aquifer setting. Geological input would be especially useful in stygobite dispersal studies because dispersal depends upon habitat continuity associated with geological dispersal corridors, and is limited where rocks that do not provide a suitable habitat form geological barriers. Stygobite studies are of benefit to hydrogeology because stygobite distributions can provide information on ground¬water-surface water interaction and aquifer connectivity over a range of spatio-temporal scales. Future studies using DNA analysis of stygobites may provide much more detailed information on hydraulic connectivity within and between aquifers. There is also potential for the development of stygobites as indicators of groundwater quality. The biogeochemical function of stygobites is of interest to both hydrogeologists and ecologists. Studies have demonstrated that stygobites graze biofilms and bacteria but their role in biogeochemical cycles is still not fully understood. Ecosystem services provided by groundwater fauna depend upon their abundance and biomass. Future studies using hydrogeological data (e.g. borehole packer techniques) may provide an improved understanding of where in aquifers stygobites live and how many there are, which would be an important step towards assessing the significance of their role in biogeochemical cycling of nutrients and carbon

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia

Abstract In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models’ procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.</jats:p