The assessment of the diversity of habitats and the characterisation of the functional trophic groups of benthic macroinvertebrate communities of some rivers of Serra do Cipó (MG) were the main objectives of this study. The available trophic resources and the types of substrata were characterised along with the structure and composition of their using functional trophic groups. Serra do Cipó is a watershed divisor of the São Francisco and Doce River basins, including a series of streams and rivers, of good water quality and well preserved ecological characteristics. Samples were collected in Cipó, Peixe and Preto do Itambé rivers, besides the Indaiá and Capão da Mata streams at 26 sampling stations, during the rainy (February) and dry (October) seasons of 1998, using "Kicking nets" of 0.125 mm mesh size. The group of collectors (Baetidae, Leptophlebiidae and Leptohyphidae) was the most abundant, followed by collector-predators (Hydrophilidae, Ceratopogonidae, Chironomidae-Tanypodinae), and detritivorous-herbivores (Oligochaeta). The riparian vegetation, together with the aquatic macrophytes, are the substrata containing the highest richness of functional trophic groups and the higher habitat diversity. The results suggest that the use of functional trophic groups, together with habitat evaluation, are efficient tools in the evaluation of the diversity of benthic macroinvertebrates, particularly in altitudinal lotic ecosystems.Key words: benthic macroinvertebrates, functional trophic groups, bioindicators, river ecology, habitat diversity. RESUMO Diversidade de habitats e grupos tróficos funcionais na Serra do Cipó, sudeste do BrasilEste trabalho teve por objetivo avaliar a diversidade de habitats e caracterizar os grupos tróficos funcionais das comunidades de macroinvertebrados bentônicos em alguns rios na Serra do Cipó, MG. Foram caracterizados os recursos tróficos disponíveis e os tipos de substrato nos habitats amostrados, a composição de grupos tróficos funcionais que os utilizam e a estrutura da comunidade de macroinvertebrados bentônicos. A Serra do Cipó constitui-se em um divisor de águas das bacias do Rio São Francisco e do Rio Doce e engloba uma série de córregos e rios, com características ecológicas ainda bem preservadas e águas de boa qualidade. Foram amostrados os rios Cipó, Peixe e Preto do Itambé, além dos córregos Indaiá e Capão da Mata ao longo de 26 estações amostrais. As amostras foram coletadas nos períodos de chuva (fevereiro) e seca (outubro) de 1998, utilizando-se "Kicking nets" com malha de 0,125 mm. Os resultados evidenciaram que o grupo dos coletores (Baetidae, Leptophlebiidae e Leptohyphidae) foi o mais abundante, seguido pelos coletores-predadores (Hydrophilidae, Ceratopogonidae, Chironomidae-Tanypodinae) e detritívoros-herbívoros (Oligochaeta). A avaliação da diversidade de habitats permitiu caracterizar a vegetação ripária, juntamente com as Rev. Brasil. Biol., 61(2)

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A general characterization of the water quality of representative rivers of Serra do Cipó, State of Minas Gerais, Brazil is provided as well as the composition and distribution of benthic macroinvertebrates, mainly Plecoptera, Ephemeroptera, Trichoptera and Diptera (Chironomidae). These data are used as a basis to propose a river classification for the area, comprising three major categories: undisturbed waters (Class 1), with no evidence of human influences and showing high taxa richness; waters with intermediate disturbances (Class 2), showing some degree of change in the quality of their trophic resources, due mainly to the influence of human activities (e.g., deforestation, sewage discharges); and disturbed waters (Class 3), showing evidence of eutrophication, although still preserving some diversity of benthic organisms. This proposed classification system, although broad and simple, is believed to provide the necessary basic scientific information to allow for definition of conservation policies in the area, thus contributing to the preservation of rivers and their associated biota.

The aim of this study was to evaluate the resistance to ten antimicrobial agents and the presence of bla ( TEM1 ) gene of Gram-negative bacteria isolated from three natural oligotrophic lakes with varying degrees of anthropogenic influence. A total of 272 indigenous bacteria were recovered on eosin methylene blue medium; they were characterized for antimicrobial resistance and identified taxonomically by homology search and phylogenetic comparisons. Based on 16S ribosomal RNA sequences analysis, 97% of the isolates were found to be Gram-negative bacteria; they belonged to 11 different genera. Members of the genera Acinetobacter, Enterobacter, and Pseudomonas predominated. Most of the bacteria were resistant to at least one antimicrobial. The incidence of resistance to beta-lactams, chloramphenicol, and mercury was high, whereas resistance to tetracycline, aminoglycosides, and nalidixic acid was low. There was a great frequency of multiple resistances among the isolates from the three lakes, although no significant differences were found among the disturbed and reference lakes. The ampicillin resistance mechanism of 71% of the isolates was due to the gene bla ( TEM1 ). Our study suggests that multiresistant Gram-negative bacteria and the bla ( TEM1 ) gene are common in freshwater oligotrophic lakes, which are subject to different levels of anthropogenic inputs.

In order to verify the cascade-system effect in benthic macroinvertebrate communities, and the implications for policy making and proposals for conservation and sustainable use of the lower portion of São Francisco river basin (Bahia State, Brazil), a three-reservoir cascade system including two stretches downstream were studied during dry (June, 1997) and rainy (March, 1998) periods. The dominant groups found were Mollusca (Melanoides tuberculata), Oligochaeta, and Chironomidae larvae. Low Shannon-Wiener and Pielou index values were found, but with no significant difference between the sampling periods. However, density and taxonomic richness were significantly different (t (0.05; 31) = -2.1945; p < 0.05; e t (0.05; 31) = -3.0600; p < 0.01) between the sampling periods, with a reduction in the number of taxa and macroinvertebrate abundance during the rainy period. An increasing gradient in benthic macroinvertebrate community structures was noted along the reservoir cascade from the first reservoir (Apolônio Sales), followed by a decrease downstream from the third reservoir of the system (Xingó). Despite the negative consequences of rapid proliferation of dams, which have caused widespread loss of freshwater habitats, the reservoir cascade system promoted an increase in benthic macroinvertebrate diversity, due to water-quality improvement along the system. Key words: benthic macroinvertebrates, reservoir, biodiversity assessment, reservoir cascade concept, São Francisco river. RESUMO Avaliação da biodiversidade de macroinvertebrados bentônicos ao longo de uma cascata de reservatórios no baixo rio São Francisco (nordeste do Brasil)Com o objetivo de determinar o efeito da cascata de reservatórios nas comunidades de macroinvertebrados bentônicos e sua possível implicação para a definição de políticas e propostas para conservação e uso sustentável da porção baixa da bacia do rio São Francisco (Bahia, Brasil), amostragens foram realizadas em três reservatórios e dois trechos a jusante do último reservatório, durante os períodos de seca (junho de 1997) e chuvas (março de 1998

Mining negatively affects the environment by producing large quantities of metallic tailings, such as those contaminated with arsenic, with harmful consequences for human and aquatic life. A culture-independent molecular analysis was performed to assess the prokaryotic diversity and community structural changes of the tropical historically metal-contaminated Mina stream (MS) and the relatively pristine Mutuca stream (MTS) sediments. A total of 234 bacterial operational taxonomic units (OTUs) were affiliated with 14 (MS) and 17 (MTS) phyla and 53 OTUs were associated with two archaeal phyla. Although the bacterial community compositions of these sediments were markedly distinct, no significant difference in the diversity indices between the bacterial communities was observed. Additionally, the rarefaction and diversity indices indicated a higher bacterial diversity than archaeal diversity. Most of the OTUs were affiliated with the Proteobacteria and Bacteroidetes phyla. Alphaproteobacteria, Gemmatimonadetes and Actinobacteria were only found in the MS clone library. Crenarchaeal 16S rDNA sequences constituted 75 % of the MS archaeal clones, whereas Euryarchaeota were dominant in the MTS clones. Despite the markedly different characteristics of these streams, their bacterial communities harbor high diversity, suggesting that historically mining-impacted sediments promote diversity. The findings also provide basis for further investigation of members of Alphaproteobacteria as potential biological indicators of arsenic-rich sediments.

Coarse particulate organic matter is often broken down by specialist shredder invertebrates in temperate streams. In some tropical streams, larger, non-specialist, omnivorous fauna, (macroconsumers), particularly decapod shrimps and crabs, have been found to process coarse particulate matter. Larger shrimps and fish may also prey on or inhibit smaller invertebrates. Depending on the relative importance of larger and smaller fauna in leaf processing and in predatory interactions, we could expect that exclusion of larger fauna could either result in a decrease in leaf processing (if they were important in shredding or bioturbation) or increase in leaf processing if they negatively affected smaller shredders. We tested this by excluding fauna of different sizes from leaf peaks using bags with different sizes of mesh -0.2 mm (exclusion of most fauna), 2 mm (exclusion of larger fauna), and 10 mm (access to most fauna). Bag effect on leaf processing was minimized by constructing the bags of the same, fine, material, and sewing a relatively small window of the required mesh size. The experiment was conducted on two occasions in three streams of the urban forest of Parque Estadual da Pedra Branca, city of Rio de Janeiro. The three streams differed in larger fauna of shrimps (Macrobrachium potiuna), crabs, tadpoles, and fish. Packs were incubated for six time intervals and the rate of leaf processing calculated as the exponential rate of loss of leaf material. Rate of leaf processing was faster in bags with the largest mesh size; the rates in the other two mesh sizes were not statistically different. Rates varied between experiments and among streams. We could not attribute the faster leaf processing to any particular component of the larger fauna; the patterns of differences among streams and between experiments were not associated with particular taxa. There was no general trend of fewer smaller fauna in the presence of macroconsumers; the few smaller taxa that were different between mesh sizes were variously less and more abundant in the 10-mm mesh bags compared to the 2-mm. Known shredders were rare in the smaller fauna; the mining chironomid Stenochironomus was common, but was apparently not affected by larger fauna and apparently Handling editor: B. Oertli did not increase leaf processing. We conclude that macroconsumers and not smaller fauna had a positive effect on leaf processing, and this confirms a pattern observed in some other coastal Neotropical streams.

Scale and frequency of changes in a lake's physical structure, light dynamics, and availability of nutrients are closely related to phytoplankton ecology. Since phytoplankton assemblages were first described, phytoplankton ecologists concluded that these assemblages provide insight into phytoplankton responses to environmental changes. Objectives of this study were to investigate ecology of phytoplankton during a complete hydrological cycle in the deepest natural lake in Brazil, Dom