International Review of Hydrobiology最新文献

Healthy populations of salmonids are integral for the functioning of ecosystems and a valuable part of sociocultural identities. Past declines were attributed to anthropogenic stressors, raising concern about the sustainability of populations. Accordingly, many salmonids are listed on red lists and protected by national legislation. One region where salmonid populations are threatened is Northern Spain, the most southern distribution of both the Atlantic salmon (protected under the EU Habitat Directive) and the brown trout. Here, we collated ~700 biomonitoring samples of both species collected across 177 sites over a 10-year period (2010–2019) to describe ongoing trends in these species and to relate them to site characteristics and potential drivers which may modulate these trends. We showed that both species have declined substantially, with stocked individuals constituting the majority of both populations. Natural reproduction was almost entirely absent for the brown trout (<1%), but present in the Atlantic salmon (~20%). Both species expressed distinct spatial patterns, likely related to their stocking and habitat preferences. As a result, we not only underline alarming conditions of both species, but also question the effectiveness of currently employed stocking efforts. Given that both species are of increasing conservation concern, river basin-specific analyses are required to identify limiting factors on which conservation actions can be taken. In the evaluated river systems, identified targets include dam removal and pollution reduction, concomitant to the implementation of more effective stocking practices to reduce dependency and maximise conservation benefits for aquatic populations.

Human activities, including the mining industry, have considerably degraded water habitats worldwide. Acidification has severely affected aquatic environments and biodiversity by altering food webs and reducing species richness. The study area in southern Poland is unique in addressing the effects of mining-related acidification on biodiversity in freshwater ecosystems along a broad pH gradient (2.4–9.6) in mining lakes. Study was designed to test for effect of human induced acidification. Using multivariate ordination techniques, we analyzed how variations in invertebrate composition are related to environmental factors. The results indicated that pH, hardness, total dissolved solids, and the content of ammonia and calcium were significantly associated with the distribution of invertebrates in the studied mining lakes. The highest iron content, relatively high values of conductivity, and chlorides were found in the extremely acidic mining lakes. A clear trend in decreasing density with decreasing pH was observed for taxa such as Oligochaeta, Chironomidae, Glossiphonidae, and certain taxa of snails. However, the density of other taxa such as Lestidae, Libellulidae, Caenidae, Sialidae, Helodidae, Hydrophilidae, and Polycentropodidae increased with decreasing pH. Specific communities were found with increasing acidity. Therefore, a further increase in acidity will probably cause a stronger decline in most of taxa and their density, and on water chemistry (e.g., calcium concentration, nitrites, and hardness). The data yielded offer an opportunity to fill knowledge gaps on acidic stress concerning less-studied environments such as mining lakes and link environmental pollution with communities, which is especially important, because aquatic forest habitats are especially exposed to different climatic factors and threats.

The progressive loss of biodiversity in rivers and their floodplains has not yet been stopped. With the European Biodiversity Strategy and the goal of restoring at least 25,000 km of free-flowing European rivers by 2030, the first important step has been taken. Now we need to be able to effectively demonstrate a reversal of biodiversity loss as well as the success of urgently needed restoration measures. This special issue presents twelve results of current river and floodplain restoration and evaluation approaches that have successfully combined hydromorphological restoration measures with interdisciplinary research. We report comprehensively on the challenges and opportunities that river and floodplain restoration can offer to protect the biodiversity and ecosystem functioning of these habitats.

Within the EU LIFE-Nature project ‘River and floodplain revitalisation Emmericher Ward’, three small temporary waters and a former gravel pit were connected by a side channel running parallel to the river Rhine through former groyne fields. The initial status of macrozoobenthos, fish, avifauna, flora, vegetation, and habitats before and their development after implementation of the project's measures were recorded and compared. The monitoring years 2018 and 2019 were exceptionally dry and accompanied by an extremely low runoff in the Rhine and the side channel. These conditions likely affected the development of habitats and species populations in the new side channel. The new side channel showed intensive morphodynamic development and differentiation of its structures. While the more complex vegetation and habitat types appeared as mostly species-poor initial stages, short-lived species-rich pioneer habitats such as annual mud banks in the water exchange area were already established. Two years after the implementation, the benthic invertebrate fauna was still predominantly species-poor and dominated by neozoans. Occasionally, representatives of the more sensitive EPT fauna (Ephemeroptera, Plecoptera, Trichoptera) were already detected but were, in general, strongly underrepresented in the main stream. Low colonisation potential, nonpermanent flow, and lack of river wood limit the development of the macrozoobenthos community. The relative abundance of rheophilic fish species increased in the project area and high juvenile fish densities proved the function as a nursery habitat. As pioneer species of riverine landscapes, sand martins and little ringed plovers colonised the new structures already in the first year. The initial state of the side channel represented a typical dynamic pioneer habitat pattern of a sandy lowland river, which was almost absent in the Lower Rhine area. The new habitats were quickly colonised by pioneer flora and fauna, but the potential for more demanding and complex communities was restricted by the poor structural and biological states of the Lower Rhine.