International Review of Hydrobiology最新文献

Natural rivers offer riparian habitats to many highly specialised, rare, and endangered insect species and are extremely important for ecosystem services. In the past, these ecosystems have been heavily degraded by anthropogenic use and run the risk of losing their favourable ecological conditions. For this reason, restoration measures are urgently needed and strongly demanded politically as well as legally, for instance, through the European Union Water Framework Directive. This is also important because nowadays, we are confronted with increasing insect declines. Using a Before-After-Control-Impact approach, we studied the effects of a riverbank restoration (complete removal of a large gravel embankment) on carabid assemblages of riparian habitats along the Mulde River in central Germany in 2017 and 2019. We collected 86 species in three site types (managed, natural, and restored) by pitfall trapping and found numerous species of conservation concern. Our analyses showed that the percentage of species of conservation concern was significantly higher after restoration in restored compared to managed sites. Furthermore, after restoration, the percentage of indicator species for natural sites increased significantly in restored sites while the abundance of indicator species characteristic for managed sites decreased in these sites. Species assemblage composition significantly changed in response to restoration approaching near-natural conditions. The creation of habitat mosaics with open gravel and sand patches as well as the re-establishment of river dynamics were likely the most significant drivers for restoration success. We were able to show how important the restoration of riparian habitats is to promote populations of endangered, rare, and specialised species. Our results highlight that positive effects of a river restoration measure can be observed after a relatively short time. Ground beetles can thus be viewed as early indicators for restoration success, but we see a need for long-term monitoring to evaluate long-term effects reliably.

Restoring natural fluvial dynamics is fundamental for sustaining biodiversity and functional integrity of river and floodplain ecosystems. In Central Europe, however, pervasive river regulation and bank protection have greatly impaired ecosystem functioning and many water bodies fail to achieve a good ecological status within the European Water Framework Directive. The “Free Moving Rivers” approach seeks to restore the ecological integrity of rivers and floodplains by creating appropriate conditions for natural fluvial dynamics. Principal goals of the approach include removing artificial constraints on river processes and expanding the river corridor to restore natural river habitats and structures. Lacking, however, are complementary tools that evaluate and predict changes to ecosystem services (ESSs) after implementation. Here, we describe a case study of the Ammer river in Bavaria, Germany, to (i) calculate the extent of the “Free Moving Rivers” corridor, and (ii) assess changes to ESSs of a proposed river restoration measure under two alternative land-use scenarios. To do this, we apply the River Ecosystem Service Index (RESI), whereby individual ESSs are assessed in a spatially explicit way. We show how a proposed implementation of the “Free Moving Rivers” approach enhances three investigated ESSs: flood retention, sediment balance and habitat provision. We conclude that RESI is a potentially useful tool with wide applicability for restoration planning that synthesises floodplain complexity in such a way that facilitates decision making.

Spring helocrenes are a unique aquatic environment with high biotic diversity. Although environmental heterogeneity has traditionally been assumed to explain the high species richness of spring habitats, this assumption has never been properly tested. Here, we sampled macroinvertebrates from two calcareous helocrenes in Slovakia with visually distinguishable mesohabitat heterogeneity. We hypothesise that macroinvertebrate beta diversity significantly increases with environmental heterogeneity even at a small within-site spatial scale. We also examined four species-trait categories, that is, active or passive dispersers and habitat specialists or generalists. Significant spatial structuring of environmental heterogeneity was found at one site, whereas the other site did not show a clear spatial pattern. Strong associations were found between beta diversity of all species trait categories and environmental heterogeneity at the first site, while there were virtually no associations at the second site. Specialists were not spatially structured at any of the sites examined. Our results suggest that invertebrate beta diversity responds positively to environmental heterogeneity at a site by also tracking spatial structuring of abiotic conditions. However, the response may vary depending on the dispersal mode and habitat specialisation of the invertebrates.

Large wood (LW) is an integral part of natural river ecosystems and determines their ecological integrity by modulating hydromorphology and providing habitats. Hence, LW installations are a common restoration measure in large rivers, even if effects on biodiversity are ambiguous or unknown for ecosystem functioning. Here we quantified the hydromorphological, biological, and functional effects of LW 8 months after installation in a large gravel-bed river. Both morphological and flow diversity increased strongly by 821% and 127%, respectively. Similarly, fish abundance increased nearly 10-fold, and macroinvertebrate diversity increased by 35%. Ecosystem functions benefited from LW installation and increased significantly (e.g., by up to 390% for bacterial production) at sites influenced by LW compared to those without LW. Our results highlight the role of the bark habitat of LW that increased the direct effects of LW via the provision of new habitat and stimulated ecosystem-wide processes. Our integrative approach evaluating the success of LW installations in a large river revealed cascading effects from the provisioning of new habitats, the increase of species diversity to higher ecosystem functioning. It also demonstrated that hydromorphological parameters or community composition alone are insufficient to quantify the complex effects of LW installation, which underlines the necessity to evaluate restoration success with different measures.

Large wood structures, such as wood fragments, debris jams, or entire trees, create flow and habitat diversity in rivers. A key flow feature associated with such structures is the wake, characterised by a core zone of reduced velocity and shear layers at its margins. Wakes are largely controlled by geometric and structural properties of the wood. In the present study, the flow patterns and turbulence created by different wood structures were compared at two study sites: naturally eroded and fragmented oaks (Site A) and artificial poplar installations (Site B). Flow and turbulence were quantified using pointwise velocity measurements with acoustic Doppler velocimeters (ADVs) and surface particle tracking velocimetry (SPTV). The measured flow patterns exhibited similarities with shallow porous wakes that feature fluid advection through the structure into the wake core downstream. Two additional features of wood structures were identified in the present study: (i) the growth of the shear layers was hindered by bed friction like for shallow mixing layers and (ii) the presence of a tree stem and sediment deposit in the wake centre delayed or even suppressed the interaction of the shear layers and vortex street formation similar to a wake-splitter plate. Methodologically, the combined ADV/SPTV measurement approach and the use of analytical models for shallow mixing layers proved to be highly valuable to decipher the complex flow patterns around wood structures in the field.

Riverbanks are very dynamic habitats for riparian vegetation strongly influenced by fluvial and geomorphic processes. This habitat type was severely reduced in the past by river straightening and bank stabilisation. Restoration and establishment of new floodplain streams promote this habitat, but a directed succession to later stages was observed many times. Our study aimed to analyse whether the often observed directed succession of the streambank vegetation after restoration implementation could be reversed by a natural flood along a newly created floodplain stream. We investigated the effects of a natural flood in 2013 and different prerestoration conditions on species development in the riparian zone. Vegetation was studied along 12 transects in four different sections from 2011 to 2014. Species composition differed strongly between the sections. Species richness was lowest in a newly dug steep section with high morphological dynamics and highest on wider flat streambanks. Changes during the years reflecting different hydrological events varied between sections. The high natural flood in 2013 reduced the cover of the herb layer and increased bare ground, which led in most sections to a loss of nontarget species. Total target species richness did not change due to the natural flood, while target species showed a high turnover rate. In the following year, however, the flood-induced development of species composition, in general, was reversed. Natural floods changed abiotic and biotic conditions along the streambank, but they did not accelerate ecological restoration towards predefined target ecosystems. However, they were necessary to preserve the needed dynamic vegetation changes and species turnover to hinder the succession to later stages dominated by a few species. Our study shows that riparian vegetation near the streambank can be monitored most effectively in cross-profile transects, both in the long-term and event-related.

Background: Rapid development of technologies increases the possibility of technological enhancements of human beings, e.g., in their cognitive skills or physical fitness. Attitudes towards such enhancements may result in their social acceptance or rejection.

Participants and procedure: One hundred and thirty-nine young Polish adults participated in the study. Participants completed the designed Technological Enhancements Questionnaire (TEQ) and questionnaires to measure values, the scientistic worldview, and the accepted versions of humanism.

Results: The study showed a one-dimensional TEQ structure and its satisfactory reliability. Attitudes towards technological enhancements correlated positively with achievement, self-direction in thought, power over resources, the scientistic worldview, and the evolutionary version of humanism. They also correlated negatively with tradition and the liberal version of humanism.

Conclusions: The TEQ questionnaire is a short, reliable tool to measure attitudes towards technological enhancements. This preliminary study provided some significant results, but future work to validate the questionnaire is needed.

Freshwater ostracods are commonly found in temporary ponds and lakes, surviving drought periods by producing resting eggs. We investigated the hatching phenology of ostracod resting eggs from the sediments of temporary floodplain lakes, considering both the taxonomic distance between species and their functional traits, such as carapace size (length and height) and shape, valve ornamentation, and reproductive mode. In addition, we tested the hypotheses: (1) that the hatching time is more similar between congeneric ostracod species than between noncongeneric species; (2) that differences in hatching time between congeneric species are often related to differences in functional traits; (3) that both species composition and functional traits composition of hatchlings change over the incubation time, but with a reduction in the variability over time. The experiment was conducted for 98 days in the laboratory, and the microcosms were monitored weekly. The first hatching of an ostracod was recorded during the second week of incubation after hydration of the sediments. A total of 12 ostracod species hatched, belonging to the families Cyprididae and Candonidae. The above three hypotheses were corroborated. The time between inundation and first hatching was mostly similar for congeneric species in the genus Chlamydotheca, but was different between some species of Strandesia, which might be owing to differences in functional traits. The species composition and functional trait composition of the hatched ostracods were significantly different over the 14 weeks of incubation due to the different hatching phenology of different species. Furthermore, our results show that both taxonomic distance and functional traits can influence the hatching time of ostracod resting eggs from temporary floodplain lakes. Thus, future studies addressing the hatching phenology of ostracod resting eggs (and resting stages from other invertebrates) should also emphasize the use of functional traits.

We studied seed transport in the Upper Eider River (Northern Germany). Our main questions were: Diaspores of what species are transported in the river and which of them remain viable after the drift? Could functional species traits be used as predictors for the survival of plant propagules in course of water transport? The water body of the Upper Eider River was sampled for plant diaspores at two bridges with each four traps changed weekly during the whole year. Samples were separated into two equal groups. Each two samples per bridge and week were dried and seeds were counted manually. The other two samples were spread on sterilised soil for germination. Species composition and community weighted trait means were compared for dried samples (total transport) and seedlings (germinated after drift). About half of the species and 1/10 of the seeds were able to survive hydrochorous transport. Species traits (community weighted means) were not reliable predictors for survival of species during the hydrochorous transport, but the majority of traits reflect the differences between the transport pools of seeds and seedlings. Small seed size, ruderal life strategy, and high light preference correlate positively with germinability after the drift, while large-seeded species adapted to endozoochory tend to lose viability during hydrochory. Dispersal of terrestrial plants with running water in the studied small river system is a highly stochastic event. We did not find evidence that specific adaptations to hydrochory significantly contribute to its success. Nevertheless, a few functional traits can increase the probability for the species to pass through the ecological filter “hydrochory.” Among those traits are (i) small seed size (less vulnerability for mechanical stress), (ii) generalist dispersal mode, less dependent on other particular vectors, and (iii) ruderal life strategy.