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Aim:The aim was to compare the kinetics of decomposition and the colonization of leaf litter of two plant species, the native Talauma ovata (pinha-dobrejo) and the exotic Saccharum officinarum (sugarcane), by aquatic macroinvertebrates; Methods: From each substrate, three recipients of colonization were taken from a stream, and the specimens identified to the lowest taxonomic level on days 7, 15, 34, 44, 61 and 75. The debris was weighed at the beginning and end of the experiment and determined their cell wall fractions; Results: The coefficients of mineralization indicated higher velocity decay of organic matter refractory in T. ovata. There was no difference in taxonomic structure of macroinvertebrates, between the two substrates, but the community exhibited distinct functional feeding groups in the peak of colonization, with a greater number of shredders in T. ovata. The successive states of decomposition of the two plant detritus showed distinct macroinvertebrate densities; Conclusions: The amount and state of the plant biomass were important factors influencing the density and diversity of the macroinvertebrate fauna throughout the process of organic decomposition.

Resumo Colonização de substratos artiiciais por macroinvertebrados aquáticos em córregos de baixa ordem.A natureza do substrato é um dos fatores que determina a presença e o estabelecimento da biota bentônica nos ecossistemas aquáticos. A colonização de substratos artiiciais por macroinvertebrados em avaliações das comunidades tem sido frequentemente utilizada como ferramenta pelas facilidades operacionais que oferece. O presente estudo teve por inalidade veriicar se há, ou não, seletividade da macrofauna por diferentes tipos de substratos artiiciais. Recipientes de colonização contendo diferentes substratos foram imersos em três pequenos córregos da região de São Carlos -SP por 30 dias. Para avaliar a seletividade de cada tipo de substrato uma comparação foi feita entre a fauna colonizadora e a fauna residente em cada córrego. A análise dos dados indicou que todos os substratos artiiciais utilizados apresentaram diferentes seletividades nos córregos estudados. Os resultados apontam para a necessidade de prévio conhecimento das características do corpo d'água objeto de estudo (por ex. tipo de substratos do leito, vegetação do entorno, etc.) para a escolha do tipo de substrato artiicial que será mais bem colonizado por determinado grupo de macroinvertebrados. Palavras-chave: Colonização; Insetos Aquáticos; Sistemas Lóticos; Substratos artiiciais AbstractOne of the factors that determine the presence and establishment of the benthic biota in aquatic ecosystems is the nature of the available substrate. The colonization of artiicial substrates for macroinvertebrates has often been used as a tool in environmental assessments by operating facilities it provides. The present study aimed to determine whether or not macrofauna exhibit selectivity for different types of artiicial substrates. Colonization recipients containing different substrates were immersed in three small streams in the region of São Carlos, São Paulo, for 30 days. To evaluate selectivity for each substrate type, a comparison was made between the colonizing and resident fauna in each stream. Data analysis indicated that macroinvertebrate fauna exhibited selectivity for different artiicial substrate types in the streams studied. These results point to the need for knowledge of water body characteristics prior to study (e. g., types of substrates in stream beds and surrounding vegetation, etc.) in order to choose the types of artiicial substrates that are better colonized by speciic groups of macroinvertebrates.

ABSTRACT. The aim of this study is to evaluate the kinetics of aerobic decomposition of Saccharum officinarum and Talauma ovata leaves. For each species, decomposition chambers (leaves and water) were set up, which were maintained under controlled conditions. Each sampling day (1, 7, 15, 30, 39, 58, 72 and 90 days), the concentrations of total organic carbon, pH and electrical conductivity (EC) were determined in the dissolved fraction, while the mass and cell wall fractions (CWF) were determined in the particulate fraction. The pH stabilization of the chambers with T. ovata and S. officinarum leaves occurred in alkaline (ca. 8 -8.5) and close to the neutrality (ca. 7 -7.5) environment, respectively. The EC values were on average 1.6 times higher in incubations with T. ovata leaves. The mass loss did not differ between the species (mean = 53.85%), however the decay coefficient was higher for S. officinarum (k 4 = 0.007 day ) were similar. S. officinarum decomposed faster due to its high concentrations of energetic compounds of interest to the microbiota. The slower decomposition of T. ovata may have occurred due to the presence of secondary compounds with negative effects to the microorganisms.Keywords: riparian zone, mass loss, mineralization, dissolved organic carbon, particulate organic carbon.Cinéticas da decomposição aeróbia de Talauma ovata e Saccharum officinarum RESUMO. O objetivo deste estudo foi avaliar as cinéticas da decomposição aeróbia de folhas de Talauma ovata e Saccharum officinarum. Para cada espécie foram montadas câmaras de decomposição (folhas e água) que foram mantidas sob condições controladas. A cada dia amostral (1, 7, 15, 30, 39, 58, 72 e 90 dias), as concentrações de carbono orgânico total, pH e condutividade elétrica (CE) foram determinadas na fração dissolvida, enquanto a massa e as frações de parede celular (FPC) foram determinadas na fração particulada. A estabilização do pH das câmaras com folhas de T. ovata e S. officinarum ocorreram em meio básico (ca. 8 -8,5) e próximo à neutralidade (ca. 7 -7,5), respectivamente. Os valores de CE foram em média 1,6 vezes maiores nas incubações com folhas de T. ovata. A perda de massa não diferiu entre as espécies (média = 53,85%). No entanto, o coeficiente de decaimento foi maior para as folhas de S. officinarum (k 4 = 0,007 dia -1 ) que para T. ovata (k 4 = 0,005 dia -1 ). As perdas de massa da FPC (média = 50,16%) e seus respectivos coeficientes (0,0090 dia -1 ) foram similares. S. officinarum decompôs mais rapidamente devido às elevadas concentrações de compostos energéticos de interesse para a microbiota. A decomposição mais lenta de T. ovata pode ter ocorrido pela presença de compostos secundários com efeitos negativos sobre os micro-organismos.Palavras-chave: zona ripária, perda de massa, mineralização, carbono orgânico dissolvido, carbono orgânico particulado.

The diet of shredder chironomid larvae depends on the local and temporal conditions of the food resources. We analysed the gut content of shredder chironomid larvae that colonised the leaf litter of three riparian species: Hedychium coronarium, Pteridium arachnoideum and Magnolia ovata. We hypothesised that the differences in the decomposition rates of leaf litter species influence the consumption of plant tissue by shredder chironomid taxa over time. We incubated perforated bottles with each leaf species within four low-order streams during 1st, 3rd, 7th, 22nd, 36th, 55th and 85th day of exposure. We used an analysis of covariance (ANCOVA) to compare differences in the percentage of AFDM (ash-free dry mass) and AOM (amorphous organic matter) among leaf litter species. To verify differences in the larvae abundance, we used a general linear model, and to test if there were feeding preferences for AFDM and AOM, we used the adapted Paloheimo selectivity index. Magnolia ovata presented a higher quantity of AOM followed by H. coronarium and P. arachnoideum. Pteridium arachnoideum showed a higher AFDM followed by H. coronarium and M. ovata. The larvae abundance was different among plant species and varied significantly with AFDM and AOM quantities. The consumption of plant tissue by shredder chironomid differed temporarily and among riparian species, where facultative or strict shredders showed strong association with different leaf litter species. The amount of AFDM and AOM in plant tissues explained these differences. We highlighted that shredder chironomids displayed an important role as co-participants in the decomposition process.