Due to decades of persistent anthropogenic pressures, lowland rivers represent one of the most severely impaired habitats in Europe. Despite improved water quality, novel stressors, particularly climate change, are emerging with most lowland rivers suffering from past hydromorphological degradation. We aim to elucidate how such degradation alters the biological response in multiple-stressor environments, as this has rarely been considered in studies documenting long-term development of anthropogenically impacted rivers. Here, benthic macroinvertebrates, water quality and hydroclimatic variables were monitored over a period of two decades in nine of the largest Czech rivers. Detailed data on hydromorphological degradation allowed us to track distinct patterns in rivers with high and low levels of degradation. Temporal changes in environmental variables showed similar patterns in both site groups, characterised by reduced organic and nutrient pollution but increased hydroclimatic and salinity stress. 150 % increase in total abundance, especially in abundance and richness of sediment-dwelling and non-native taxa was found in both site groups. While the increase in abundance was due to improved water quality and rising water temperature, the longer duration of minimal flows had a negative effect on species richness, hampering species gain particularly at highly degraded sites. Our results provide novel evidence that degree of hydromorphological degradation modifies long-term macroinvertebrate responses to anthropogenic pressures. Less degraded sites displayed several favourable changes, such as 27 % increase in total and 23 % increase in potamal indicator richness, and stabilisation of the assemblages with few functional changes. In contrast, highly degraded sites experienced 9 % reduction in evenness, 235 % increase in proportion of non-native taxa and functional reorganisation, changes congruent with continuous deterioration. While overall water quality at studied sites has improved, consequences of climate change and high degree of hydromorphological degradation limit biotic recovery in multiple-stressor lowland rivers.

Large branchiopods are key biota of temporary pools in Central European lowlands. Due to land use changes, they are among the most threatened aquatic invertebrates in Europe. The lack of information on the main drivers of species distribution hinders effective protection and conservation prioritisation. We selected eight branchiopod species with representative data on their occurrence in the northern Pannonia to identify the most important drivers of their distribution and to predict their distribution in unexplored temporary pools across the Pannonian region of southern Slovakia, south-eastern Czech Republic, and eastern Austria. Data on pool size and isolation, soil characteristics, land use and climate were used to generate species distribution models using five modelling techniques and ensemble predictions. The distribution of species was mainly affected by the proportion of arable land within the pool (e.g. Triops cancriformis, Leptestheria dahalacensis), land use (e.g. Eubranchipus grubii, Lepidurus apus) and distance from the river (e.g. Branchinecta ferox and Chirocephalus carnuntanus). Wetland size and habitat isolation were also important for some species, mainly for Branchipus schaefferi and Imnadia yeyetta, respectively. As we focused on a climatically homogeneous area, climatic conditions only had the most important effect on the distribution of species that have their distribution limit in northern Pannonia (B. ferox, C. carnuntanus, I. yeyetta). Overall, the diversity of large branchiopods increased with pool size, while decreased with distance to a river and habitat isolation. As some distribution patterns emerged repeatedly in the models, the effective protection can be simplified to consider species that require contrasting conditions. Particular attention should be paid to ephemeral wetlands on arable land, crucial habitats for large branchiopods, yet lacking any protection. Our results can contribute to better conservation of large branchiopods by facilitating surveys of species in understudied areas and improving the knowledge on the species environmental niches.

The temporal dynamics of aquatic invertebrate communities are known to be influenced by the length of hydroperiods, but only temporary wetlands with relatively long hydroperiods have been well studied. By contrast, few studies have focused on ephemeral wetlands, primarily represented by extremely ephemeral rock pools. In Central Europe, many ephemeral wetlands develop spontaneously directly on arable land, often on the sites of former natural wetlands that have been drained and converted to agricultural land. Here, we focused on aquatic invertebrates in 10 ephemeral pools over periods of inundation to desiccation on arable land in southern Moravia. Despite relatively short hydroperiods of 5-11 weeks, we observed significant changes in community composition, including species replacement. Dynamics differed between macroinvertebrates and microcrustaceans and between different macroinvertebrate feeding and dispersal groups. Predation pressure increased over time and was highest during drying. Passive dispersers were most abundant during the middle phase, whereas the abundance of active dispersers increased throughout the hydroperiod. Because no significant effect of any environmental factor was detected on community change, we hypothesized that community dynamics were driven by differences in species traits and biotic interactions rather than by the changing environment. This study fills a knowledge gap on the temporal dynamics of aquatic invertebrate communities in temporary wetlands by investigating wetlands with short, but not extremely ephemeral, hydroperiods.

The resting eggs of large branchiopods do not hatch all at once during a hydroperiod; instead, a fraction of the eggs are left dormant to cope with unstable conditions in temporary wetlands. In order to maximize fitness, the fraction that terminates diapause is modified by signals indicating habitat suitability and biotic interactions. Here, in a laboratory experiment, we investigate the effect of conspecific cues on the hatching time and hatching rate of resting eggs from Triops cancriformis (Bosc, 1801). While hatching time was not significantly affected by conspecific cues, the effect of these cues on hatching rate was highly significant, with hatching rate increasing with increasing concentration of conspecific cues. This indicates that alongside environmental factors, conspecific cues also have the power to terminate the diapause of Triops resting eggs. In addition to indicating suitable conditions, such cues could also act as a mechanism for reducing egg cannibalism by adults, which are predominantly benthic feeders. As such, our results suggest that the response of large branchiopod encysted embryos to conspecific chemical cues could have evolved as a response to the feeding strategy of their adult stages; however, more research will be needed to fully understand the mechanism(s) behind this response.

Výsledky tohto výskumu su prvotným nahľadom do zloženia spolocenstva a vlastnosti prostredia poľných mokradi, ktorý predstavuje zaklad pre nadvazujuci výskum.

Přispěvek se zabýva výzkumem spolecenstev vodnich bezobratlých vcetně velkých lupenonožců v polnich rozlivech jižni Moravy. Popisuje sukcesi v průběhu jara odražejici se ve změnach složeni těchto spolecenstev a ekologicke faktory, ktere ji ovlivňuji.