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Against the backdrop of recent climate change issues, the intensity of dry periods is increasing in semi-arid environments due to high temperatures, evaporation and a shortage of precipitation in summer. The Tafna catchment, which is located in north-western Algeria and is characterised by a Mediterranean climate with a sub-dry tendency, has been subject to severe and prolonged dry periods. In order to understand the impact of prolonged dry periods on biogeochemical processes and nutrient exchange between surface water (SW) and hyporheic water (HW) within the (study) catchment, four sets of samples were taken upstream of the Tafna wadi during low-water (LW) periods over two years (2014–2015). Nitrate, nitrite, ammonium and chloride were measured in surface water (SW) and hyporheic water (HW) at depths of 30, 60 and 100 cm. The results showed a significant loss of nitrate and a considerable increase in ammonium in the hyporheic zone (HZ) during these severe conditions. This could be related to (i) high rates of denitrification and (ii) the process of dissimilatory nitrate reduction to ammonium (DNRA). This study indicated that a severe drought directly affects the nitrogen cycle that occurs in a hyporheic zone (HZ), and thus affects the functioning of this area relative to the wadi system as a whole. [ABSTRACT FROM AUTHOR]

Transition to novel environments, such as groundwater colonization by surface organisms, provides an excellent research ground to study phenotypic evolution. However, interspecific comparative studies on evolution to groundwater life are few because of the challenge in assembling large ecological and molecular resources for species-rich taxa comprised of surface and subterranean species. Here, we make available to the scientific community an operational set of working tools and resources for the Asellidae, a family of freshwater isopods containing hundreds of surface and subterranean species. First, we release the World Asellidae database (WAD) and its web application, a sustainable and FAIR solution to producing and sharing data and biological material. WAD provides access to thousands of species occurrences, specimens, DNA extracts and DNA sequences with rich metadata ensuring full scientific traceability. Second, we perform a large-scale dated phylogenetic reconstruction of Asellidae to support phylogenetic comparative analyses. Of 424 terminal branches, we identify 34 pairs of surface and subterranean species representing independent replicates of the transition from surface water to groundwater. Third, we exemplify the usefulness of WAD for documenting phenotypic shifts associated with colonization of subterranean habitats. We provide the first phylogenetically controlled evidence that body size of males decreases relative to that of females upon groundwater colonization, suggesting competition for rare receptive females selects for smaller, more agile males in groundwater. By making these tools and resources widely accessible, we open up new opportunities for exploring how phenotypic traits evolve in response to changes in selective pressures and trade-offs during groundwater colonization., (© 2023 John Wiley & Sons Ltd.)