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RESUMO Com uma distribuição geográfica histórica alargada em zonas costeiras, ambientes de transição e fluviais do Oceano Atlântico tropical, o manatim (manati das Índias Ocidentais, peixe-boi ou iguaragua do Brasil colonial) era bastante valorizado. As fontes documentais e iconográficas dos séculos XVI e XVII mostram-nos que era usado como alimento, para fins medicinais, para produzir utensílios ou como animal de estimação, mas seu valor económico e simbólico foi igualmente dominante. A sobre-exploração contínua conduziu ao desaparecimento de muitas populações de manatins, os quais hoje enfrentam o risco de extinção. Pretendemos explorar do ponto de vista da história ambiental marinha o significado pragmático e simbólico dos manatins numa ligação próxima aos valores atribuídos aos rios e cursos de água. Esperamos também contribuir para colocar manatins e o seu ecossistema no centro de uma discussão sobre contextos e interações ambientais e socioculturais das sociedades indígenas e coloniais nas Américas do período moderno. ABSTRACT The manatee (manati of the West Indies, also called manatim or iguaragua in colonial Brazil) was highly valued and presented a broad historical geographic distribution in coastal, transitional and fluvial areas of the tropical Atlantic Ocean. Documental and iconographic sources of the 16th and 17th centuries show us that it was used as food and for medicinal purposes, to manufacture tools or even as a pet. Moreover, its economic and symbolic value was equally relevant. Continued overexploitation led to the disappearance of many populations of manatees, which are currently at the brinck of extinction. We will explore, from the point of view of marine environmental history, the pragmatic and symbolic meaning of the manatee in close connection to the importance given to rivers and watercourses. We also expect to contribute to place manatees and their ecosystem at the center of the discussion about the environmental and sociocultural contexts and interactions of indigenous and colonial societies in the Americas of the modern period.

This work addresses multiple human stressors and their impacts on fish assemblages of the Drava and Mura rivers in southern Austria. The impacts of single and multiple human stressors on riverine fish assemblages in these basins were disentangled, based on an extensive dataset. Stressor configuration, i.e. various metrics of multiple stressors belonging to stressor groups hydrology, morphology, connectivity and water quality were investigated for the first time at river basin scale in Austria. As biological response variables, the Fish Index Austria (FIA) and its related single as well as the WFD biological- and total state were investigated. Stressor-response analysis shows divergent results, but a general trend of decreasing ecological integrity with increasing number of stressors and maximum stressor is observed. Fish metrics based on age structure, fish region index and biological status responded best to single stressors and/or their combinations. The knowledge gained in this work provides a basis for advanced investigations in Alpine river basins and beyond, supports WFD implementation and helps prioritizing further actions towards multi-stressor restoration- and management.

Habitat fragmentation and land use changes are causing major biodiversity losses. Connectivity of the landscape or environmental conditions alone can shape biodiversity patterns. In nature however local habitat characteristics are often intrinsically linked to a specific connectivity. Such a link is evident in riverine ecosystems where hierarchical dendritic structures command related scaling on habitat capacity. We experimentally disentangled the effect of local habitat capacity (i.e. the patch size) and dendritic connectivity on biodiversity in aquatic microcosm metacommunities by suitably arranging patch sizes within river like networks. Overall more connected communities that occupy a central position in the network exhibited higher species richness irrespective of patch size arrangement. High regional evenness in community composition was found only in landscapes preserving geomorphological scaling properties of patch sizes. In these landscapes some of the rarer species sustained regionally more abundant populations better tracking their own niche requirements compared to landscapes with homogeneous patch size or landscapes with spatially uncorrelated patch size. Our analysis suggests that altering the natural link between dendritic connectivity and patch size strongly affects community composition and population persistence at multiple scales. The experimental results are demonstrating a principle that can be tested in theoretical metacommunity models and eventually be projected to real riverine ecosystems. © 2013 by The University of Chicago.

This work addresses human stressors and their impacts on fish assemblages at pan-European scale by analysing single and multiple stressors and their interactions. Based on an extensive dataset with 3105 fish sampling sites, patterns of stressors, their combination and nature of interactions, i.e. synergistic, antagonistic and additive were investigated. Geographical distribution and patterns of seven human stressor variables, belonging to four stressor groups (hydrological-, morphological-, water quality- and connectivity stressors), were examined, considering both single and multiple stressor combinations. To quantify the stressors' ecological impact, a set of 22 fish metrics for various fish assemblage types (headwaters, medium gradient rivers, lowland rivers and Mediterranean streams) was analysed by comparing their observed and expected response to different stressors, both acting individually and in combination. Overall, investigated fish sampling sites are affected by 15 different stressor combinations, including 4 stressors acting individually and 11 combinations of two or more stressors; up to 4 stressor groups per fish sampling site occur. Stressor-response analysis shows divergent results among different stressor categories, even though a general trend of decreasing ecological integrity with increasing stressor quantity can be observed. Fish metrics based on density of species ‘intolerant to water quality degradation’ and ‘intolerant to oxygen depletion” responded best to single and multiple stressors and their interactions. Interactions of stressors were additive (40%), synergistic (30%) or antagonistic (30%), emphasizing the importance to consider interactions in multi-stressor analyses. While antagonistic effects are only observed in headwaters and medium-gradient rivers, synergistic effects increase from headwaters over medium gradient rivers and Mediterranean streams to large lowland rivers. The knowledge gained in this work provides a basis for advanced investigations in European river basins and helps prioritizing further restoration and management actions.

WOS:000317245800058 ,Humankind is prone to exceeding biogeochemical limits to freshwater resources in the face of rapidly increasing demands of global population and economic growth Without measurable indicator of sustainability. Such indicators with a differing Methodological complexity were developed for rivers in order to estimate water quantity required to secure their long-term productive state. Generally, environmental flow requirement method was applied to economically significant rivers Where intensive fisheries take place and was defined as the sum of flow requirements that fish stocks demand. Recently, more robust methods for environmental flow requirement have been developed that consider multiple environmental factors such as demands of other organisms (e.g. invertebrates and water birds), ecosystem Structure, (e.g., biogeoclimate, geomorphology, flora, fauna, biodiversity and flood plain) and ecosystem function (e.g. nutrient cycles, primary production and ecosystem respiration). This study assesses the concept of environmental flow requirement in the context of Big Melen water transfer project as a case study.

Available information pertaining to water temperature in riverine ecosystems is examined and consolidated into an overview that describes the spatial and temporal variation in water temperature, the importance of water temperature in lotic ecosystems, the measurement and modelling of water temperature, anthropogenic factors that modify water temperature, the effects of temperature changes on the physical and chemical characteristics of water; and on aquatic organisms and ecosystems. Methods for assessing the effects of temperature changes on aquatic organisms are discussed and current water temperature guidelines for the protection of aquatic ecosystems are outlined. This paper highlights the complexity of water temperature in the aquatic environment and the importance of understanding the spatio-temporal variability in water temperature and the variable responses of aquatic organisms to thermal stress. Anthropogenic modifiers of the thermal regime, which include heated discharges, flow modifications, riparian vegetation removal and global climate change; present ongoing threats to aquatic ecosystems. Whilst Northern Hemisphere information on water temperature is plentiful, this overview has identified the huge gap that exists in temperature-related data in South Africa. Without baseline data on water temperature and the thermal requirements of aquatic organisms, it is extremely difficult to adequately manage aquatic ecosystems. The risk of increasingly harsh conditions caused by greater water demands and climate change accentuates the need for a greater understanding of the thermal conditions in aquatic ecosystems in South Africa and the requirements and triggers of the associated aquatic biota. Future directions for thermal research are described.Keywords: water temperature, riverine ecosystems, rivers, thermal regimes, biotic responses, aquatic organisms