Identifying the current and future status of freshwater connectivity corridors in the Amazon Basin

The Amazon Basin features a vast network of healthy, free-flowing rivers, which provides habitat for the most biodiverse freshwater fauna of any basin globally. However, existing and future infrastructure developments, including dams, threaten its integrity by diminishing river connectivity, altering flows, or changing sediment regimes, which can impact freshwater species. In this study, we assess critical rivers that need to be maintained as freshwater connectivity corridors (FCCs) for selective freshwater species—long-distance migratory fishes and turtles (both with migrations >500 km) and river dolphins. We define FCCs as river stretches of uninterrupted river connectivity that provide important riverine and floodplain habitat for long-distance migratory and other species and that maintain associated ecosystem functions. We assessed more than 340,000 km of river, beginning with an assessment of the connectivity status of all rivers and then combining river status with models of occurrence of key species to map where FCCs occur and how they could be affected under a scenario of proposed dams. We identified that in 2019, 16 of 26 very long (>1000 km) rivers are free-flowing but only 9 would remain free-flowing if all proposed dams are built. Among long and very long rivers (>500 km), 93 are considered FCCs. Under the future scenario, one-fifth (18) of these long and very long FCCs—those that are of critical importance for long-distance migrants and dolphins—would lose their FCC status, including the Amazon, the Negro, Marañ on, Napo, Ucayali, Preto do Igap o Açu, Beni, and Uraricoera rivers. To avoid impacts of poorly sited infrastructure, we advocate for energy and water resources planning at the basin scale that evaluates alternative development options and limits development that will impact on FCCs. The results also highlight where corridors could be designated as protected from future fragmentation

A database of freshwater fish species of the Amazon Basin

The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation

Fonctionnement hydrologique superficiel de la Réserve naturelle nationale du Marais de Lavours = Hydrological functioning of the Reserve naturelle nationale du Marais de Lavours

The manager of the Lavours Natural Reserve attends since the late eighties to a drying of parts of the peat bog. To better understand the ecological processes, a better understanding of the hydrological functioning is necessary. The reserve was prospected to upgrade the cartography of the drainage network and to provide a vision of the water flow dynamic. Further, the evolution of network drainage through time was explained by digitalizing historic maps available. Historical values of altitude were compared to recent data to estimate the subsidence of the peat bog. The overall results show the significant impact of recent developments on the drying of peat, whether across the marsh (ditches, valves) or larger scale (channelization of the Rhone River). Highlighting hydrological processes in the reserve can guide the manager in his actions to preserve the environment

Les communautés de poissons du bassin de l'Amazone : habitats aquatiques, gradients de diversité, facteurs et processus associés et options de conservation

La biodiversité aquatique du bassin versant de l'Amazone, le plus grand système fluvial au monde et le plus diversifié en espèces, reste encore relativement mal répertoriée malgré toute l'attention que le bassin suscite au niveau de la communauté scientifique internationale. La répartition spatiale des espèces dans le bassin, et notamment celle des poissons d'eau douce, reste encore assez peu documentée, très parcellaire et dispersée entre les pays et institutions, associée à une taxonomie parfois confuse. Il en va de même pour la distribution des habitats aquatiques et des formes fluviales associées à l'échelle de l'ensemble du bassin, la dimension de celui-ci limitant l'acquisition de données de terrain. Améliorer la connaissance sur la répartition de la biodiversité et des habitats aquatiques dans le bassin versant de l'Amazone est pourtant une étape cruciale afin de pouvoir appréhender les facteurs et processus à l'origine de la diversification des espèces, identifier les zones à protéger prioritairement (hotspots de biodiversité) et mieux évaluer la vulnérabilité des espèces face aux changements globaux. Ce travail de thèse découle de l'ensemble de ces constats et vise à réduire les lacunes importantes de connaissances soulevées.The aquatic biodiversity of the Amazon basin, the largest and most species rich river basin on Earth, is still relatively poorly documented despite all the attention received from the international scientific community. Knowledge about the spatial distribution of species, and in particular of freshwater fishes, is very fragmented and dispersed between countries and institutions. The distribution of river forms has been also poorly explored at the scale of the entire basin, its continental dimension limiting the acquisition of field data. Improving the knowledge on the distribution of biodiversity and aquatic habitats in the basin is however a crucial step to better understand the factors and processes behind species diversification, identify priority areas for conservation (biodiversity hotspots) and assess the species vulnerability to global changes. This thesis work aims to reduce these significant knowledge gaps

Fonctionnement hydrologique superficiel de la Réserve naturelle nationale du Marais de Lavours

Hydrological functioning of the Réserve naturelle nationale du Marais de Lavours. - The manager of the Lavours Natural Reserve attends since the late eighties to a drying of parts of the peat bog. To better understand the ecological processes, a better understanding of the hydrological functioning is necessary. The reserve was prospected to upgrade the cartography of the drainage network and to provide a vision of the water flow dynamic. Further, the evolution of network drainage through time was explained by digitalizing historic maps available. Historical values of altitude were compared to recent data to estimate the subsidence of the peat bog. The overall results show the significant impact of recent developments on the drying of peat, whether across the marsh (ditches, valves) or larger scale (channelization of the Rhône River). Highlighting hydrological processes in the reserve can guide the manager in his actions to preserve the environment.Le gestionnaire de la réserve naturelle assiste depuis la fin des années quatre-vingts à un assèchement de certaines parties du marais. Pour mieux appréhender les processus écologiques en cours, une meilleure connaissance du fonctionnement hydrologique est nécessaire. Une campagne de prospection des fossés a permis la réactualisation de la cartographie du réseau de drainage, de dégager une vision dynamique des circulations hydrauliques superficielles et de délimiter les masses d'eau en présence. L'évolution du réseau de drains est représentée grâce à l'analyse de plusieurs cartes anciennes. Le tassement de la tourbe au cours du temps est estimé par la comparaison de cotes d'altitude anciennes et récentes sur certaines zones du marais. L'ensemble des résultats montre l'impact important des aménagements récents sur l'assèchement de la tourbière, que ce soit à l'échelle du marais (fossés, vannes) ou à plus grande échelle (canalisation du Rhône). La mise en évidence des processus hydrologiques en cours dans la réserve peut guider le gestionnaire dans ses actions pour préserver ce milieu.Jézéquel Céline. Fonctionnement hydrologique superficiel de la Réserve naturelle nationale du Marais de Lavours. In: Bulletin mensuel de la Société linnéenne de Lyon, hors-série numéro 3, 2014. Bilan de 30 ans d'études scientifiques dans le marais de Lavours (1984-2014) pp. 30-41

Modelling built infrastructure heights to evaluate common assumptions in aquatic conservation

Built infrastructure, such as dams and weirs, are some of the most impactful stressors affecting aquatic ecosystems. However, data on the distribution and characteristics of small built infrastructure that often restrict fish movement, impede flows, and retain sediments and materials, remain limited. Collection of this necessary information is challenged by the large number of built infrastructure with unknown dimensions (e.g., height), which means scientists and practitioners need to make assumptions about these characteristics in research and decision-making. Evaluating these common assumptions is essential for advancing conservation that is more effective. We use a statistical modelling approach to double the number of small (= 1.0 m. The opposite is true for fish species that cannot pass >= 2.0 m, where assuming all built infrastructure without height data are impassable results in a 7-fold increase in fragmentation compared to the scenario with modelled heights to attribute built infrastructure passability. Our findings suggest that modelled height data leads to better understanding of river fragmentation, and that knowledge of different fish species' abilities to pass a variety of built infrastructure is essential to guide more effective management strategies. Our modelling approach, and results, are of particular relevance to regions where efforts to both remediate and remove built infrastructure is occurring, but where gaps in data on characteristics of built infrastructure remain, and limit effective decision making

The global geography of fish diadromy modes

Aim Geographical gradients in resource production are likely to translate into macroecological patterns in the biodiversity of migratory organisms, but few studies have addressed this question at a global scale. Here, we tested a hypothesis based on uncoupled latitudinal gradients in marine and freshwater primary productivities aimed at explaining where (e.g., at which latitude) and at which stage of the life cycle (larvae, amphidromy; juvenile, catadromy; or adult, anadromy) migration from ocean to freshwater occurs (diadromy). Location Global. Time period Current. Major taxa studied Fishes. Methods We modelled, using multinomial regressions, the proportion of catadromous, anadromous and amphidromous species in 994 river basins as a function of freshwater and marine net primary productivities (NPP; in milligrams of carbon per square metre per day) and additional biotic and abiotic variables. Using data extracted from the Global Biodiversity Information Facility (GBIF) database, we tested whether diadromous, catadromous and amphidromous species differed with respect to the NPP of their marine and freshwater occurrences. Results Among diadromous species, anadromous species are present in higher proportions when conditions for growth are more favourable in the sea (higher productivity, higher temperature and lower number of competitors) than in freshwaters. The model reconstructs the latitudinal pattern observed in the proportion of anadromous species, including an asymmetry between the Northern and Southern Hemispheres. According to GBIF occurrences, the ratio of marine over freshwater productivity is higher for anadromous species compared with catadromous and amphidromous species. Main conclusions Our results support the hypothesis stating that migration between ocean and freshwater occurs by choosing the biome that optimizes pre-reproductive growth and is one more example of the importance of primary productivity in shaping large-scale community patterns. This result suggests that some diadromous fish populations and species may suffer from anticipated climate change if interbiome productivity gradients are affected

Refinement of biomonitoring of urban water courses by combining descriptive and ecohydrological approaches

Two approaches are proposed for developing adapted metrics, proposing realistic and sustainable ecologic objectives, and suggesting a management strategy for stream rehabilitation. The first approach implemented a harmonisation system of French standardized biotic indices. The second one was based on the development of functional traits (FTrs), which were defined by oligochaete assemblages inhabiting coarse surface sediments and the hyporheic system. The harmonisation system allowed to define a weighted general ecological quality. The FTrs characterized an ecological potential (EP) resulting from interactions between physical factors (dynamics of hydrologic exchanges between surface water and groundwater) and chemical factors. An example of using both approaches at the same urbanized site is presented and serves for planning of rehabilitation activities. The benefits, drawbacks and progress of both approaches are discusse

Major shifts in biogeographic regions of freshwater fishes as evidence of the Anthropocene epoch

Animals and plants worldwide are structured in global biogeographic regions, which were shaped by major geologic forces during Earth history. Recently, humans have changed the course of events by multiplying global pathways of introduction for nonindigenous species and propagating local species extirpations. Here, we report on how introductions and extirpations have changed the distributions of freshwater fishes worldwide and how it affected their natural biogeographic regions. We found major shifts in natural regions, with the emergence of an intercontinental region arising from the fusion of multiple faunas, which we named Pan-Anthropocenian Global North and East Asia (PAGNEA). The PAGNEA region is evocative of the Pangea supercontinent, as flows of introductions show that dispersal has become possible again across multiple continents, suggesting that human activities have superseded natural geological forces. Our results constitute evidence on the expected modification of biostratigraphic boundaries based on freshwater fish, which are abundant in the fossil record, thereby supporting the concept of the Anthropocene epoch