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Protecting riparian vegetation around streams is vital in reducing the detrimental effects of environmental change on freshwater ecosystems and in maintaining aquatic biodiversity. Thus, identifying ecological thresholds is useful for defining regulatory limits and for guiding the management of riparian zones towards the conservation of freshwater biota. Using nationwide data on fish and invertebrates occurring in small Brazilian streams, we estimated thresholds of native vegetation loss in which there are abrupt changes in the occurrence and abundance of freshwater bioindicators and tested whether there are congruent responses among different biomes, biological groups and riparian buffer sizes. Mean thresholds of native vegetation cover loss varied widely among biomes, buffer sizes and biological groups: ranging from 0.5% to 77.4% for fish, from 2.9% to 37.0% for aquatic invertebrates and from 3.8% to 43.2% for a subset of aquatic invertebrates. Confidence intervals for thresholds were wide, but the minimum values of these intervals were lower for the smaller riparian buffers (50 and 100 m) than larger ones (200 and 500 m), indicating that land use should be kept away from the streams. Also, thresholds occurred at a lower percentage of riparian vegetation loss in the smaller buffers, and were critically lower for invertebrates: reducing only 6.5% of native vegetation cover within a 50‐m riparian buffer is enough to cross thresholds for invertebrates. Synthesis and applications. The high variability in biodiversity responses to loss of native riparian vegetation suggests caution in the use of a single riparian width for conservation actions or policy definitions nationwide. The most sensitive bioindicators can be used as early warning signals of abrupt changes in freshwater biodiversity. In practice, maintaining at least 50‐m wide riparian reserves on each side of streams would be more effective to protect freshwater biodiversity in Brazil. However, incentives and conservation strategies to protect even wider riparian reserves (~100 m) and also taking into consideration the regional context will promote a greater benefit. This information should be used to set conservation goals and to create complementary mechanisms and policies to protect wider riparian reserves than those currently required by the federal law.

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The biomonitoring of aquatic ecosystems in developing countries faces several limitations, especially related to gathering resources. The present study aimed at comparing the responses of fish and benthic macroinvertebrates to environmental change, to identify which group best indicates the differences between reference and impacted streams in southern Brazil. We determined reference and impacted sites based on physical and chemical variables of the water. For the analysis and comparison of biological responses, we calculated 22 metrics and submitted them to a discriminant analysis. We selected from this analysis only six metrics, which showed that the two studied assemblages respond differently to environmental change. A larger number of metrics were selected for macroinvertebrates than for fish in the separate analysis. The metrics selected for macroinvertebrates in the pooled analysis (i.e., fish and macroinvertebrates together) were different from those selected in the separate analysis for macroinvertebrates alone. However, the metrics selected for fish in the pooled analysis were the same selected in the separate analysis for fish alone. The macroinvertebrate assemblage was more effective for distinguishing reference from impacted sites. We suggest the use of macroinvertebrates as bioindicators of Neotropical streams, especially in situations in which time and money are short.

Considerando a necessidade de monitoramento das águas subterrâneas utilizadas para o consumo humano, este estudo avaliou a qualidade da água de poços artesianos rurais, localizados no Assentamento Pedro Ramalho, Mundo Novo, Mato Grosso do Sul. Amostras de água foram obtidas em janeiro/2012 e setembro/2013, em dois poços artesianos. Foram determinados parâmetros físico-químicos (alumínio, cobre, cor, cloreto, cromo total, ferro, fluoreto, manganês, nitrito, pH, sólidos dissolvidos totais, sulfato e zinco) e microbiológico (NMP de coliformes totais  e de coliformes termotolerantes, bactérias heterotróficas e Escherichia coli) para os dois poços. Os valores registrados para cada parâmetro foram confrontados com os limites estabelecidos pela legislação brasileira. Apenas a água do Poço 1 apresentou valores de pH inferiores ao estabelecido pela Portaria no 2914/2011 e valores de manganês acima do valor máximo permitido pela Resolução CONAMA nº 396. Os demais parâmetros atenderam os valores limites preconizados pelas legislações. Os resultados apresentados evidenciam a necessidade de monitoramento continuo da água dos poços artesianos do Assentamento Pedro Ramalho, uma vez que foram registradas irregularidades que inspiram preocupações à saúde pública dos moradores.