Multispecies assemblages and multiple stressors: Synthesizing the state of experimental research in freshwaters

Recent decades have witnessed a sharp biodiversity decline in freshwaters due to multiple stressors. The presence of multiple stressors is expected to affect community structure and interactions in freshwater ecosystems, with subsequent functional consequences. We synthesized the state of experimental, manipulative multiple-stressor studies that focused on multispecies assemblages in freshwaters. Compared to rivers and lakes, wetland and groundwater ecosystems have received much less attention in identified multiple-stressor research. Most of the identified studies investigated combinations of abiotic stressors (e.g., nutrients, pesticides, heavy metals, warming, altered flow and sedimentation) on microbes and invertebrates while biotic stressors and vertebrates have been largely overlooked. The responses of community structure (e.g., alpha diversity, biomass, and abundance), some community/ecosystem functions (e.g., photosynthesis and autotrophic activity, leaf litter degradation), and morphological traits like body size and growth forms were frequently investigated. We observed a clear gap in biotic interactions under multiple-stressor conditions, which, although difficult to study, could impede a deeper mechanistic understanding of how multiple stressors affect freshwater assemblages and associated ecological processes. Although information on ecosystem recovery pathways following restoration is critical for freshwater management, few studies were designed to provide such information, signifying the disconnections between multiple-stressor research and environmental practice. To bridge these gaps, researchers and environmental practitioners need to work together to identify key stressors and interactions at different spatial and temporal scales and prioritize stressor management. Such collaborations will enhance the translation of multiple-stressor research into efficient management strategies to protect and restore freshwater ecosystems

Multispecies assemblages and multiple stressors: Synthesizing the state of experimental research in freshwaters

Recent decades have witnessed a sharp biodiversity decline in freshwaters due to multiple stressors. The presence of multiple stressors is expected to affect community structure and interactions in freshwater ecosystems, with subsequent functional consequences. We synthesized the state of experimental, manipulative multiple-stressor studies that focused on multispecies assemblages in freshwaters. Compared to rivers and lakes, wetland and groundwater ecosystems have received much less attention in identified multiple-stressor research. Most of the identified studies investigated combinations of abiotic stressors (e.g., nutrients, pesticides, heavy metals, warming, altered flow and sedimentation) on microbes and invertebrates while biotic stressors and vertebrates have been largely overlooked. The responses of community structure (e.g., alpha diversity, biomass, and abundance), some community/ecosystem functions (e.g., photosynthesis and autotrophic activity, leaf litter degradation), and morphological traits like body size and growth forms were frequently investigated. We observed a clear gap in biotic interactions under multiple-stressor conditions, which, although difficult to study, could impede a deeper mechanistic understanding of how multiple stressors affect freshwater assemblages and associated ecological processes. Although information on ecosystem recovery pathways following restoration is critical for freshwater management, few studies were designed to provide such information, signifying the disconnections between multiple-stressor research and environmental practice. To bridge these gaps, researchers and environmental practitioners need to work together to identify key stressors and interactions at different spatial and temporal scales and prioritize stressor management. Such collaborations will enhance the translation of multiple-stressor research into efficient management strategies to protect and restore freshwater ecosystems.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655Leibniz‐GemeinschaftGerman Federal Ministry of Education and Research (BMBF)Peer Reviewe

Future large hydropower dams impact global freshwater megafauna

Dam construction comes with severe social, economic and ecological impacts. From an ecological point of view, habitat types are altered and biodiversity is lost. Thus, to identify areas that deserve major attention for conservation, existing and planned locations for (hydropower) dams were overlapped, at global extent, with the contemporary distribution of freshwater megafauna species with consideration of their respective threat status. Hydropower development will disproportionately impact areas of high freshwater megafauna richness in South America, South and East Asia, and the Balkan region. Sub-catchments with a high share of threatened species are considered to be most vulnerable; these are located in Central America, Southeast Asia and in the regions of the Black and Caspian Sea. Based on this approach, planned dam locations are classified according to their potential impact on freshwater megafauna species at different spatial scales, attention to potential conflicts between climate mitigation and biodiversity conservation are highlighted, and priorities for freshwater management are recommended

More exposure opportunities for promoting freshwater conservation

1. Freshwater ecosystems have a higher percentage of threatened and extinct species than terrestrial or marine realms, but remain under-represented in conservation research and actions arguably as a consequence of less popularity and promotion. 2. Cover images of conservation journals were used as a proxy of exposure and potential promotion opportunities provided for different ecosystems and species. To examine whether articles related to cover images received more attention, citations and Altmetric scores of cover-featured articles were compared with non-featured ones within the same host journal issue. 3. Freshwater ecosystems (10.4%) were featured less often than marine (15.2%) or terrestrial (74.4%) ecosystems on covers of 18 conservation journals from 1997 to 2016. All 15 most featured species are from terrestrial or marine ecosystems. 4. In addition, cover-featured studies showed higher citations and Altmetric scores than non-featured ones within the same host journal issue, indicating that cover-featured articles received more attention. Further investigations are needed to examine the relationship (i.e. whether there is a true causality) between being featured on the cover, and citations and Altmetric scores received by articles, as well as potentially resulting in greater conservation efforts. Nevertheless, we believe that providing exposure opportunities is likely to better inform the public about the continuing degradation of freshwater ecosystems and its impacts on human well-being, including economic loss and danger to public health. Journal editors can contribute by balancing their selection of featured ecosystems and species when opportunities arise. 5. Increasing exposure opportunities for freshwater ecosystems through various channels seems a promising approach to raise public awareness and appreciation of freshwater biodiversity. Scientists can play an active role and form an alliance with journal editors, conservation organizations, and media, to increase momentum in society for fresh waters to be experienced as essential ecosystems and prevent further degradation of freshwater habitats and biodiversity loss

More exposure opportunities for promoting freshwater conservation

Freshwater ecosystems have a higher percentage of threatened and extinct species than terrestrial or marine realms, but remain under‐represented in conservation research and actions arguably as a consequence of less popularity and promotion. Cover images of conservation journals were used as a proxy of exposure and potential promotion opportunities provided for different ecosystems and species. To examine whether articles related to cover images received more attention, citations and Altmetric scores of cover‐featured articles were compared with non‐featured ones within the same host journal issue. Freshwater ecosystems (10.4%) were featured less often than marine (15.2%) or terrestrial (74.4%) ecosystems on covers of 18 conservation journals from 1997 to 2016. All 15 most featured species are from terrestrial or marine ecosystems. In addition, cover‐featured studies showed higher citations and Altmetric scores than non‐featured ones within the same host journal issue, indicating that cover‐featured articles received more attention. Further investigations are needed to examine the relationship (i.e. whether there is a true causality) between being featured on the cover, and citations and Altmetric scores received by articles, as well as potentially resulting in greater conservation efforts. Nevertheless, we believe that providing exposure opportunities is likely to better inform the public about the continuing degradation of freshwater ecosystems and its impacts on human well‐being, including economic loss and danger to public health. Journal editors can contribute by balancing their selection of featured ecosystems and species when opportunities arise. Increasing exposure opportunities for freshwater ecosystems through various channels seems a promising approach to raise public awareness and appreciation of freshwater biodiversity. Scientists can play an active role and form an alliance with journal editors, conservation organizations, and media, to increase momentum in society for fresh waters to be experienced as essential ecosystems and prevent further degradation of freshwater habitats and biodiversity loss.Education, Audiovisual and Culture Executive Agency of the European Union: Erasmus Mundus Joint Doctorate SMART http://dx.doi.org/10.13039/501100000785Leibniz Association: Freshwater Megafauna Futures http://dx.doi.org/10.13039/501100001664Spanish Government’s María de Maeztu excellence accreditation 2018‐2022German Federal Ministry of Education and Research (BMBF)Peer Reviewe

Do alien species affect native freshwater megafauna?

1. Freshwater megafauna species (i.e., animals that can reach a body mass ≥30 kg, including fish, reptiles, mammals, and amphibians) play important roles in freshwater systems (e.g., by influencing habitat structure, trophic dynamics, or the dispersal of smaller species). As they tend to be large and charismatic, they may also function as flagship umbrella species in future freshwater conservation initiatives. Despite this, as a group they are highly threatened, and our knowledge of the nature of these threats is limited. In this study, we aim to improve our understanding of the impacts of alien species on native freshwater megafauna. 2. We undertook the first global assessment of the impacts of alien species on native freshwater megafauna using the Environmental Impact Classification for Alien Taxa (EICAT) framework. We conducted a literature review to identify published and grey literature on impacts, which we quantified and categorised by their severity and type, following the EICAT guidelines. 3. Negative impacts on native freshwater megafauna were caused by 61 alien species from a diverse range of taxonomic groups, including both freshwater and terrestrial alien species, and both vertebrates and invertebrates. They adversely affected 44 of 216 native freshwater megafauna species, including amphibians, fish, mammals, and reptiles. The Great Lakes Basin had the highest number of affected megafauna species (six of the 14 freshwater megafauna species it supports, mainly fish). Impacts occurred through a broad range of mechanisms (10 of the 12 identified mechanisms under EICAT); predation and competition were the most frequently reported mechanisms. Some impacts were relatively minor, adversely affecting the performance of individuals of native freshwater megafauna species. However, some reported impacts did cause declining populations of native freshwater megafauna species, and one impact contributed to the local extinction of the ship sturgeon (Acipenser nudiventris) in the Aral Sea. The vulnerability of native freshwater megafauna species to different types of impact varies during different life-cycle stages (egg, juvenile, and adult). 4. Our understanding of impacts posed by alien species on native freshwater megafauna is limited because data are unavailable for many regions, particularly the Global South, including hotspots for freshwater megafauna diversity such as the Amazon, Congo, Mekong, and Ganges-Brahmaputra basins. Freshwater megafauna species are often subject to multiple threats, which makes it difficult to determine the significance of alien species impacts relative to other threats such as habitat degradation and overexploitation. In addition, short-term studies are likely to be masking the severity of the impacts identified. We call for more long-term studies that attempt to identify population-level impacts, and for studies that identify impacts in data-deficient regions. 5. The EICAT assessments undertaken for this study will be reviewed by the EICAT Authority and subsequently incorporated into the IUCN EICAT database. They may be used to guide future research and conservation actions.China Scholarship Council (CSC)German Academic Exchange Service (DAAD; PRIME programme) http://dx.doi.org/10.13039/501100001655Bundesministerium für Bildung und Forschung (BMBF; 033W034A)Leibniz Association (Freshwater Megafauna Futures) http://dx.doi.org/10.13039/501100001664Peer Reviewe

Do alien species affect native freshwater megafauna?

1. Freshwater megafauna species (i.e., animals that can reach a body mass ≥30 kg, including fish, reptiles, mammals, and amphibians) play important roles in freshwater systems (e.g., by influencing habitat structure, trophic dynamics, or the dispersal of smaller species). As they tend to be large and charismatic, they may also function as flagship umbrella species in future freshwater conservation initiatives. Despite this, as a group they are highly threatened, and our knowledge of the nature of these threats is limited. In this study, we aim to improve our understanding of the impacts of alien species on native freshwater megafauna. 2. We undertook the first global assessment of the impacts of alien species on native freshwater megafauna using the Environmental Impact Classification for Alien Taxa (EICAT) framework. We conducted a literature review to identify published and grey literature on impacts, which we quantified and categorised by their severity and type, following the EICAT guidelines. 3. Negative impacts on native freshwater megafauna were caused by 61 alien species from a diverse range of taxonomic groups, including both freshwater and terrestrial alien species, and both vertebrates and invertebrates. They adversely affected 44 of 216 native freshwater megafauna species, including amphibians, fish, mammals, and reptiles. The Great Lakes Basin had the highest number of affected megafauna species (six of the 14 freshwater megafauna species it supports, mainly fish). Impacts occurred through a broad range of mechanisms (10 of the 12 identified mechanisms under EICAT); predation and competition were the most frequently reported mechanisms. Some impacts were relatively minor, adversely affecting the performance of individuals of native freshwater megafauna species. However, some reported impacts did cause declining populations of native freshwater megafauna species, and one impact contributed to the local extinction of the ship sturgeon (Acipenser nudiventris) in the Aral Sea. The vulnerability of native freshwater megafauna species to different types of impact varies during different life-cycle stages (egg, juvenile, and adult). 4. Our understanding of impacts posed by alien species on native freshwater megafauna is limited because data are unavailable for many regions, particularly the Global South, including hotspots for freshwater megafauna diversity such as the Amazon, Congo, Mekong, and Ganges-Brahmaputra basins. Freshwater megafauna species are often subject to multiple threats, which makes it difficult to determine the significance of alien species impacts relative to other threats such as habitat degradation and overexploitation. In addition, short-term studies are likely to be masking the severity of the impacts identified. We call for more long-term studies that attempt to identify population-level impacts, and for studies that identify impacts in data-deficient regions. 5. The EICAT assessments undertaken for this study will be reviewed by the EICAT Authority and subsequently incorporated into the IUCN EICAT database. They may be used to guide future research and conservation actions

Combined effects of life-history traits and human impact on extinction risk of freshwater megafauna

Megafauna species are intrinsically vulnerable to human impact. Freshwater megafauna (i.e., freshwater animals >= 30 kg, including fishes, mammals, reptiles, and amphibians) are subject to intensive and increasing threats. Thirty-four species are listed as critically endangered on the International Union for Conservation of Nature (IUCN). Red List of Threatened Species, the assessments for which are an important basis for conservation actions but remain incomplete for 49 (24%) freshwater megafauna species. Consequently, the window of opportunity for protecting these species could be missed. Identifying the factors that predispose freshwater megafauna to extinction can help predict their extinction risk and facilitate more effective and proactive conservation actions. Thus, we collated 8 life-history traits for 206 freshwater megafauna species. We used generalized linear mixed models to examine the relationships between extinction risk based on the IUCN Red List categories and the combined effect of multiple traits, as well as the effect of human impact on these relationships for 157 classified species. The most parsimonious model included human impact and traits related to species' recovery potential including life span, age at maturity, and fecundity. Applying the most parsimonious model to 49 unclassified species predicted that 17 of them are threatened. Accounting for model predictions together with IUCN Red List assessments, 50% of all freshwater megafauna species are considered threatened. The Amazon and Yangtze basins emerged as global diversity hotspots of threatened freshwater megafauna, in addition to existing hotspots, including the Ganges-Brahmaputra and Mekong basins and the Caspian Sea region. Assessment and monitoring of those species predicted to be threatened are needed, especially in the Amazon and Yangtze basins. Investigation of life-history traits and trends in population and distribution, regulation of overexploitation, maintaining river connectivity, implementing protected areas focusing on freshwater ecosystems, and integrated basin management are required to protect threatened freshwater megafauna in diversity hotspots

Adsorbate-Induced Structural Evolution of Pd Catalyst for Selective Hydrogenation of Acetylene

ACKNOWLEDGMENT: This work was financially supported by National Natural Science Foundation of China (21908002), project funded by China Postdoctoral Science Foundation (2019M660416, 2020T130045) and the Fundamental Research Funds for the Central Universities (buctrc201921, JD2004, XK1802-6). We would like to thank the UK catalysis Hub for help collecting the XAS.Peer reviewedPostprin

Environmental filtering, spatial processes and biotic interactions jointly shape different traits communities of stream macroinvertebrates

The metacommunity concept has been widely used to explain the biodiversity patterns at various scales. It considers the influences of both local (e.g., environmental filtering and biotic interactions) and regional processes (e.g., dispersal limitation) in shaping community structures. Compared to environmental filtering and spatial processes, the influence of biotic interactions on biodiversity patterns in streams has received limited attention. We investigated the relative importance of three ecological processes, namely environmental filtering (including local environmental and geo-climatic factors), spatial processes and biotic interactions (represented by interactions of macroinvertebrates and diatom), in shaping different traits of macroinvertebrate communities in subtropical streams, Eastern China. We applied variance partitioning to uncover the pure and shared effects of different ecological processes in explaining community variation. The results showed that environmental filtering, spatial processes, and biotic interactions jointly determined taxonomic and trait compositions of stream macroinvertebrates. Spatial processes showed a stronger influence in shaping stream macroinvertebrate communities than environmental filtering. The contribution of biotic interactions to explain variables was, albeit significant, rather small, which was likely a result of insufficient representation (by diatom traits) of trophic interactions associated with macroinvertebrates. Moreover, the impact of three ecological processes on macroinvertebrate communities depends on different traits, especially in terms of environmental filtering and spatial processes. For example, spatial processes and environmental filtering have the strongest effect on strong dispersal ability groups; spatial processes have a greater effect on scrapers than other functional feeding groups. Overall, our results showed that the integration of metacommunity theory and functional traits provides a valuable framework for understanding the drivers of community structuring in streams, which will facilitate the development of effective bioassessment and management strategies.Peer Reviewe