Distribuição de oligoquetas em um riacho da mata atlântica, sudestedo brasi

The oligochaetes are considered good indicators of ecological conditions and specific types of habitats. Among the factors that influence the distribution of these invertebrates are the water flow and the nature of the substrate. The aim of this study is to describe the composition and distribution of oligochaete species in a first-order stream in Atlantic Forest and try to identify if some species are associated with characteristics of particular types of habitats. In the dry season and in the rainy season, sand and litter samples in two riffle areas and two pool areas were collected in different parts along the stream using a hand net. The greatest observed richness and abundance occurred in sand in the pool, however the greatest estimated richness was obtained for litter in the pool. The Kruskal-Wallis analysis showed effect of the different types of habitat on the abundance and richness of oligochaetes. The Nonmetric Multidimensional Scaling (NMDS) and Multiresponse Permutation Procedure analysis (MRPP) indicated that the variation in the fauna composition had relation with different types of substrates. The indicator species analysis showed that Limnodrilus. hoffmeisteri was an indicator species in both the riffle sand and pool sand and Pristina americana was only an indicator in the pool sand. The high organic matter content in both sandy habitats probably favored the greater abundance of oligochaetes. The results showed that the substrate constitutes an important factor for the local distribution of these invertebrates in streams. The variation of the community structure among mesohabitats and the presence of indicator species of specific types of habitats in the stream demonstrate the importance of environmental heterogeneity for the oligochaetes fauna in forested streams. © 2015 Instituto Internacional de Ecologia. All Right reserved

Estudo da assembleia de Chironomidae (Diptera) para avaliação ecológica de riachos de baixa ordem, Minas Gerais

The use of organisms in evaluations of aquatic ecosystems enables understanding the structure and functional processes of these systems. By calculating metrics of the assemblage of Chironomidae (Diptera) from remanso and corredeira mesohabitats, this study allowed identification of the state of preservation of nine low-order streams belonging to the Marmelos stream sub-basin, located in the municipality of Juiz de Fora, Minas Gerais, Brazil. The first chapter reports the results of two experiments. The first investigated the succession of Chironomidae from samples collected in bags containing Picramnia sellowii leaves, incubated in remansos and corredeirasof three streams in forested areas for 120 days. The changes in the composition and structure of the fauna were attributed mainly to the leaf mass loss and physical heterogeneity of the detritus, especially when the leaf decomposition reached 50% (60 days), at which point the greatest richness of taxa was observed. After 30 days, the dominance of larvae of Stenochironomus possibly contributed to the greater physical fragmentation of the leaf litter. The absence of a relationship between non-mining Chironomidae and fungal biomass indicated that many larvae use the leaves only as substrate. Between the two mesohabitats, there was weak variation in the faunal composition. The second experiment, which compared the Chironomidae fauna in the bags containing leaves after decomposition for 60 days between streams in forested areas versus those in areas affected by organic pollution, detected a clear difference in the composition of taxa between the two environments. The Chironomidae metrics had a strong relation with the environmental variables that distinguished preserved and impacted streams, suggesting the use of this method to assess the environmental conditions of streams. The second chapter investigates whether the metrics of the Chironomidae assemblage differ between remansos and corredeirasin response to different land uses (forest, pasture and urban) in low-order streams, in the dry and rainy seasons. It was found that the taxon composition of both mesohabitats and seasons was the metric with greatest sensitivity to land use, suggesting that the use of this metric of one or the other mesohabitat or season of the year for the biomonitoring enables obtaining results that are less influenced by the natural variability of the environment and reduces the time for processing of the samples. The third chapter investigates the taxonomic concordance of benthic groups identified at different taxonomic levels. Genera of Chironomidae and genera of Ephemeroptera, Plecoptera and Trichoptera (EPT) were found to be concordant in the dry and rainy seasons. The same was found for the genera of Chironomidae and species of Oligochaeta. Families of macroinvertebrates were concordant with Chironomidae genera and EPT genera only in the dry season. Similar responses to the environmental variables were attributed to the concordance between groups, while the proximity of the streams resulted in absence of an influence of the spatial variables. The numerical resolution of Chironomidae genera in both seasons was found to be effective, while this only occurred for the Oligochaeta species in the dry season. The percentage of information lost (>15%) indicates caution in using data on the presence/absence of these groups, suggesting use of this type of investigation only for rapid assessments in environments with marked differences in their preservation conditions.O uso dos organismos nas avaliações dos ambientes aquáticos possibilita o entendimento da estrutura e dos processos funcionais destes ecossistemas. A partir das métricas da assembleia de Chironomidae (Diptera) de mesohabitats de remansos e corredeiras, este estudo possibilitou identificar o estado de conservação de nove riachos de baixa ordem pertencentes à sub-bacia do Ribeirão Marmelos, localizado no Município de Juiz de Fora, MG. No primeiro capítulo, o experimento 1 investigou a sucessão de Chironomidae em sacos de folhas de Picramnia sellowii, incubados em remansos e corredeiras em três riachos florestados durante 120 dias. As mudanças na composição e estrutura da fauna foram atribuídas principalmente à perda de massa foliar e à heterogeneidade física do detrito, especialmente após a decomposição atingir 50% (60 dias), quando houve a maior riqueza de táxons. Aos 30 dias, a dominância de larvas de Stenochironomus possivelmente contribuiu para maior fragmentação física do detrito. A ausência de relação entre Chironomidae não minadores e a biomassa de fungos indicou que muitas larvas usaram as folhas apenas como substrato. Entre os mesohabitats houve fraca variação na composição da fauna. O experimento 2, que comparou a fauna de Chironomidae dos sacos de folhas aos 60 dias de decomposição entre os riachos florestados e impactados pela poluição orgânica, detectou nítida diferença na composição de táxons entre os ambientes. As métricas de Chironomidae tiveram forte relação com as variáveis ambientais que distinguiram os riachos preservados e impactados, sugerindo-se o uso desta metodologia para avaliação das condições ambientais de riachos. O segundo capítulo investigou se métricas da assembleia de Chironomidae iriam diferir entre remansos e corredeiras em resposta aos diferentes usos da terra (floresta, pastagem e urbano) em riachos de baixa ordem, no período seco e chuvoso. Foi constatado que a composição de táxons de ambos os mesohabitats e períodos foi a métrica mais sensível ao uso da terra, o que sugere que o uso desta métrica de um ou outro mesohabitat e período estacional para o biomonitoramento, possibilita a obtenção de resultados menos influenciados pela variabilidade natural do ambiente e a diminuição do tempo para o processamento das amostras. No capítulo três foi analisada a concordância taxonômica de grupos bentônicos identificados em diferentes níveis taxonômicos. Gêneros de Chironomidae e gêneros de Ephemeroptera, Plecoptera e Trichoptera (EPT) foram concordantes no período de seca e chuva. O mesmo foi constatado para gêneros de Chironomidae e espécies de Oligochaeta. Famílias de macroinvertebrados foram concordantes com gêneros de Chironomidae e gêneros de EPT somente no período seco. Respostas similares às variáveis ambientais foram responsáveis pela concordância entre os grupos, enquanto a proximidade dos riachos resultou na ausência de influencia das variáveis espaciais. Constatou-se ainda, a efetividade da resolução numérica de gêneros de Chironomidae e espécies de Oligochaeta em ambos os períodos do estudo. A porcentagem de perda de informação, (>15%) indicou cautela ao se utilizar dados de presença/ausência destes grupos, sugerindo-se sua utilização apenas para avaliações rápidas em ambientes com diferenças marcadas nas suas condições de conservação.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Estrutura e distribuição da fauna de Chironomidae (Diptera) em mesohabitats de um córrego de primeira ordem da Reserva Biológica Municipal Poço D'anta, Juiz De Fora (MG)

The aim of this study was to investigate the structure and distribution of the Chironomidae fauna in mesohabitats of litter from riff1e areas, litter from pool areas, and sediment in pool areas in a first-order Atlantic Forest stream located in southeastem Brazil. The collections were carried out in the months of July, August and September of 2007 (dry season) and January, February and March of 2008 (rainy season), using a Surber sampler (250 um mesh) for a period of 30 seconds for each mesohabitat. The samples were fixed in formaldehyde solution 4%, and then washed in current water and passed through a sieve with a 0.21mm mesh, sorted in a stereoscopic microscope and identified to genus level or morphotype. ln order to analyze the structure ofthe Chironomidae community in each mesohabitat sampled in the two periods of study, the richness, the Shannon's diversity index, Pielou's evenness and the dominance index were calculated. Cluster analysis indicated that precipitation was a factor with a great influence on the variation of the structure of the Chironomidae fauna in mesohabitats from litter in riffle areas and in pool areas, with low influence on sediment in pool areas. Through the Correspondence Analysis and the lndicator Values Method it was possible to observe the association of the taxa with specific mesohabitats and/or the seasonal period. The substrates litter and sediment were suitable to the establishment of Chironomidae larvae showing high richness and diversity. The type of substrate and the precipitation were the major factors that determined the structure and spatial and temporal distribution of the fauna. The results obtained reinforce the importance of the Riparian Forest to the heterogeneity of habitats on a local scale, a fact that allows the specie diversity in low order streams.O objetivo deste estudo foi investigar a estrutura da comunidade e a distribuição da fauna de Chironomidae em três mesohabitats: folhiço correnteza, folhiço remanso e sedimento remanso, em um córrego de primeira ordem na Mata Atlântica localizada na região sudeste do Brasil. As coletas foram realizadas nos meses de julho, agosto e setembro de 2007 (período seco) e janeiro, fevereiro e março de 2008 (período chuvoso), usando o amostrador Surber (malha 250 um) por um período de 30 segundos para cada mesohabitat. As amostras foram fixadas em formol a 4% e posteriormente no laboratório foram lavadas em peneira com malha 0,2Imm, triadas sob microscópio estereoscópico e os espécimes identificados em nível de gênero ou morfotipo. Para análise da estrutura da comunidade de Chironomidae de cada mesohabitat nos dois períodos de estudo, foram calculadas a riqueza taxonômica, a diversidade de Shannon, equidade de Pielou e o índice de dominância (ID) para cada táxon. A análise de agrupamento indicou que a pluviosidade foi um fator com forte influência na variação da estrutura da fauna de Chironomidae nos mesohabitats de folhiço em correnteza e remanso, e com menor influência no sedimento em remanso. Através da Análise de Correspondência e do Método do Valor Indicador foi possível observar a associação dos táxons com mesohabitats específicos e/ou período sazonal. Os substratos folhiço e sedimento foram favoráveis ao estabelecimento das larvas de Chironomidae apresentando alta riqueza e diversidade. O tipo de substrato e a precipitação foram os principais fatores que determinaram a estrutura e a distribuição espacial e temporal da fauna. Os resultados obtidos reforçam a importância da mata ciliar para a heterogeneidade de habitats em escala local, que favorece a diversidade de espécies em córregos de baixa ordem

Aquatic invertebrates associated with bromeliads in Atlantic Forest fragments

Abstract: Forest fragments in the state of Minas Gerais contain a large number of Bromeliaceae genera, whose cisterns accumulate water and organic matter, providing shelter and food for a wide range of organisms. However, these fragments often consist only of small patches of vegetation, making the species more vulnerable to the effects of this landscape changes. This study aimed to test the effect of the distance to the edge and of the matrix type on the structure of aquatic invertebrate communities in four morphospecies of bromeliads. Samples were collected in Atlantic Forest fragments adjacent to pasture and planted forest areas, in a region of Serra da Mantiqueira, Brazil. Of the 147 bromeliads investigated, we found 35 taxa, among which the most abundant groups were Ostracoda (4,962 individuals), Culicidae (2,358), Tanypodinae (1,164) and Scirtidae (1,043). The richness of taxa and Shannon diversity of invertebrates were similar at different distances from the edge, with variation of richness between 17 and 23 taxa and diversity between 1.25 and 1.52. The composition of the fauna in the cisterns changed between some collection sections (A vs. C, C vs. D and D vs. F), irrespective of being close to or far from the edge. There was no variation of richness (t=-1.145, df=106, p= 0.341) and diversity (t= 1.376, df= 106, p= 0.429) among samples collected from fragments next to planted forest and pasture, likely because the bromeliads studied were located on hillsides above the canopy of planted forests, and subject to similar conditions to those found in the fragments next to pastures. The results demonstrate the importance of bromeliads in maintaining the richness and diversity of the invertebrates they harbor, even in altered landscapes exposed to extreme conditions such as fragment edges