Unified Multimetric Index for the Evaluation of the Biological Condition of Streams in Southern Brazil Based on Fish and Macroinvertebrate Assemblages.

We developed MMI models that combine responses of fish and benthic macroinvertebrates for the evaluation of the biotic integrity of streams. The MMI was developed using a dataset covering stream sampling sites in the South of Brazil. Reference streams were identified based on the physical and chemical conditions and riparian vegetation. Thirty-four metrics were calculated and evaluated for their range, redundancy, and responsiveness to the environmental perturbation. We applied a robust approach to select the most sensitive metrics and MMI models based on the complexity and ability of the index in distinguishing impacted and reference sites. The four best MMI models selected are composed of different combinations of the eight metrics: % fish herbivorous, fish evenness, fish abundance, % macroinvertebrate shredder; % macroinvertebrate predator; % macroinvertebrate tolerant, % macroinvertebrate swimmer, and % macroinvertebrate burrower. All of the MMI models selected presented good performance in distinguishing reference streams from those impacted by different forms of land use. This study is one of the few attempts to use more than one biological assemblage in a single-multimetric index. Accordingly, we believe that the unified MMI we developed could be a useful tool to assist in the conservation and management of water resources in Neotropical regions, specially, in the implementation of ecological integrity tools more cost-effectively.

Plant litter dynamics in the forest-stream interface: precipitation is a major control across tropical biomes.

Riparian plant litter is a major energy source for forested streams across the world and its decomposition has repercussions on nutrient cycling, food webs and ecosystem functioning. However, we know little about plant litter dynamics in tropical streams, even though the tropics occupy 40% of the Earth's land surface. Here we investigated spatial and temporal (along a year cycle) patterns of litter inputs and storage in multiple streams of three tropical biomes in Brazil (Atlantic forest, Amazon forest and Cerrado savanna), predicting major differences among biomes in relation to temperature and precipitation regimes. Precipitation explained most of litter inputs and storage, which were generally higher in more humid biomes (litterfall: 384, 422 and 308 g m-2 y-1, storage: 55, 113 and 38 g m-2, on average in Atlantic forest, Amazon and Cerrado, respectively). Temporal dynamics varied across biomes in relation to precipitation and temperature, with uniform litter inputs but seasonal storage in Atlantic forest streams, seasonal inputs in Amazon and Cerrado streams, and aseasonal storage in Amazon streams. Our findings suggest that litter dynamics vary greatly within the tropics, but point to the major role of precipitation, which contrasts with the main influence of temperature in temperate areas.

Comparison of fish and macroinvertebrates as bioindicators of Neotropical streams.

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.

Spatial variation of the benthic community in the Corumbá reservoir, Goiás, Brazil - DOI: 10.4025/actascibiolsci.v25i1.2078 / Variação espacial da comunidade bêntica no reservatório de Corumbá, Estado de Goiás, Brasil - DOI: 10.4025/actascibiolsci.v25i1.2078

The benthic community composition and abundance were analyzed in three stations of the Corumbá reservoir. Collections were undertaken at the margin and the center of the stations, aiming to analyze the abiotic parameters affecting this community. Variables such as depth, dissolved oxygen and sediment type were the main factors that determined the benthic community structure. Fauna was abundant in the marginal region, probably because of the lower depth and higher dissolved oxygen concentrations. The opposite occurred at the central region, with the exception of the reservoir"s riverine station. This fact may be due to the shallowness of the place and the water current high speed. Oligochaeta and Chironomidae were the most frequent and abundant taxa in the Corumbá Reservoir. These results show that the benthic community in the reservoir is spatially related to depth and to dissolved oxygen

A composição e a abundância da comunidade bêntica foi analisada em três estações do reservatório de Corumbá. Foram feitas coletas na margem e no centro das estações, visando a analisar os parâmetros abióticos que influenciaram essa comunidade. Variáveis, tais como profundidade, oxigênio dissolvido e o tipo de sedimento, foram os principais fatores que determinaram a estrutura da comunidade bêntica. A fauna apresentou uma maior abundância na região marginal, provavelmente devido às menores profundidades e maiores concentrações de oxigênio dissolvido. O inverso foi verificado na região central, exceto na estação fluvial do reservatório, pois trata-se de um local raso e com maior velocidade de correnteza. Oligochaeta e Chironomidae foram os principais táxons em freqüência e abundância no reservatório de Corumbá. A partir desses resultados, pode-se sugerir que a comunidade bêntica no reservatório estudado está relacionada, espacialmente, com a profundidade e com o oxigênio dissolvido

Spatial variation of the benthic community in the Corumbá reservoir, Goiás, Brazil - DOI: 10.4025/actascibiolsci.v25i1.2078 / Variação espacial da comunidade bêntica no reservatório de Corumbá, Estado de Goiás, Brasil - DOI: 10.4025/actascibiolsci.v25i1.2078

The benthic community composition and abundance were analyzed in three stations of the Corumbá reservoir. Collections were undertaken at the margin and the center of the stations, aiming to analyze the abiotic parameters affecting this community. Variables such as depth, dissolved oxygen and sediment type were the main factors that determined the benthic community structure. Fauna was abundant in the marginal region, probably because of the lower depth and higher dissolved oxygen concentrations. The opposite occurred at the central region, with the exception of the reservoir"s riverine station. This fact may be due to the shallowness of the place and the water current high speed. Oligochaeta and Chironomidae were the most frequent and abundant taxa in the Corumbá Reservoir. These results show that the benthic community in the reservoir is spatially related to depth and to dissolved oxygen

A composição e a abundância da comunidade bêntica foi analisada em três estações do reservatório de Corumbá. Foram feitas coletas na margem e no centro das estações, visando a analisar os parâmetros abióticos que influenciaram essa comunidade. Variáveis, tais como profundidade, oxigênio dissolvido e o tipo de sedimento, foram os principais fatores que determinaram a estrutura da comunidade bêntica. A fauna apresentou uma maior abundância na região marginal, provavelmente devido às menores profundidades e maiores concentrações de oxigênio dissolvido. O inverso foi verificado na região central, exceto na estação fluvial do reservatório, pois trata-se de um local raso e com maior velocidade de correnteza. Oligochaeta e Chironomidae foram os principais táxons em freqüência e abundância no reservatório de Corumbá. A partir desses resultados, pode-se sugerir que a comunidade bêntica no reservatório estudado está relacionada, espacialmente, com a profundidade e com o oxigênio dissolvido