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Environmental influences on species' functional traits are important ecological issues to assess biodiversity. Relationships among fish abundance, their functional traits, and environmental conditions across different levels of anthropogenic impacts in a tropical Brazilian river were evaluated. We combined RLQ and fourth-corner methods, utilizing local environmental variables and the Human Footprint Index (HFI) as a human activities indicator. Three HFI levels (High, Intermediate, and Low) and short-term (1993–2009) impact changes at each location were assigned. Fish with internal fertilization and small body sizes were strongly associated with high HFI scores. Grass-dominated riparian areas were common in altered locations, whereas less altered localities exhibited the riparian cover dominated by trees. Highly altered areas showed high HFI, grass-covered riparian zones, and small-sized species with internal fertilization (e.g., Cyprinodontiformes like Poecilia vivipara, Poecilia reticulata, and Phalloceros caudimaculatus). In contrast, less altered areas had tree-lined riparian zones and medium to large-sized species with external fertilization and diverse traits. Underlying deterministic processes shape species distribution, tied to environment and traits. Filtering of traits in the most altered locations may favor small-sized species with internal fertilization. This approach, utilizing HFI and local variables to assess trait–environment relationships of riverine fish, facilitates understanding organisms' responses to environmental constraints. [ABSTRACT FROM AUTHOR]

River phytoplankton has been studied to understand its occurrence and composition since the end of the nineteenth century. Later, pioneers addressed mechanisms that affected river phytoplankton by "origin of plankton", "turbulent mixing", "flow heterogeneity", "paradox of potamoplankton maintenance" and "dead zones" as keywords along the twentieth century. A major shift came with the recognition that characteristic units in phytoplankton compositions could be linked to specific set of environmental conditions, known as the "Phytoplankton Functional Group concept" sensu Reynolds. The FG concept could successfully be applied to river phytoplankton due to its close resemblance to shallow lakes phytoplankton. The FG approach enables one to separate the effects of "natural constraints" and "human impacts" on river phytoplankton and to evaluate the ecological status of rivers. The FG classification has mainly been advocated in the context of how the environment shaped the functional composition of phytoplankton. It may be further developed in the future by a trait-based mechanistic classification of taxa into FGs, and by the exact quantification of FGs on ecosystem functioning. These improvements will help quantify how global warming and human impacts affect river phytoplankton and corresponding alterations in ecosystem functioning. [ABSTRACT FROM AUTHOR]

We examined the recovery of a fish assemblage following the catastrophic spill of highly alkaline (pH ~13) red sludge into a lowland river (i) to characterize taxonomic- and trait-based colonization of fishes in the river in the first 3 years of the recovery and (ii) to determine which structural- and trait-based variables best predicted colonization. Species richness showed comparable values to pre-disturbance state <1 year after the spill. We found only moderate changes in the dominance of the most abundant species between pre- and post-disturbance periods, and consistent changes in the relative abundance of some rare species during the post-disturbance period. Frequency of occurrence (%) of the fishes in the watershed and their relative abundance (%) proved to be the most important predictor variables in colonization, whereas trait-based variables had a less important role. Our study about one of the largest scale and most serious documented fish kill shows that both taxonomic- and trait-based structure of fish assemblages can regenerate remarkably fast in a modified river and also shows that unfortunate chemical spills provide insights into the assembly of stream fish assemblages. [ABSTRACT FROM AUTHOR]