Levantamento de macroinvertebrados aquáticos e sua função no processamento de detritos foliares em igarapés de cabeceira na Serra Bonita, Cantá-RR

• Autor(a) principal: Feitoza, Lorrane Aesha Malta
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFRR
• Texto Completo: http://repositorio.ufrr.br:8080/jspui/handle/prefix/425
• topic: Relações ecológicas; Fragmentadores; Decomposição; Igarapés da Serra Bonita; Cantá, RR; Meio ambiente; Ecological relationships; Shredders; Decomposition; Environment; CNPQ::CIENCIAS BIOLOGICAS

Studies of litter decomposition in tropical streams are scarce, and these ecosystems are under constant threat by the degradation of riparian vegetation, and may be lost in biodiversity not yet known. Studies about macroinvertebrates in Roraima are scarce, especially regarding the characterization of habitat, biological and ecological relationships of the immature stages. The aim of this study was to know the fauna of aquatic macroinvertebrates associated with submerged litter in streams of the Serra Bonita, Cantá - RR, to understand which groups participate in the allochthonous organic matter processing. It was selected three streams of the same river basin, in each one a sample point was delimited. Sampling was carried out between June and November 2012. The leaves were collected in buckets suspended at 1m from the bed of the stream. After 30 ± 2 days, the leaves were collected, weighed and placed in packages of coarse mesh (with about 5g or 5 leaves) and incubated at 30 ± 2 days on stream. After this time the packages were collected and washed under 250 μm mesh to retain the macroinvertebrates. Leaves were cut from 4 discs each, to calculate the ash-free dry weight, and the other for other analysis. Both the leaves as the discs were dried and weighed to calculate the decomposition rate based on the model of negative exponential decay (Wt = W0 -e-kt). Water abiotic parameters were also analyzed, such as temperature, pH, conductivity, dissolved oxygen, nitrite, nitrate, ammonia, total phosphorus and flow. We used the similarity index to compare the taxa in different sampling points. To verify the relationship between decomposition rate and number of macroinvertebrate and shredders, simple linear regression was applied. Were performed PCA and NMDS, whose major axes were correlated to examine whether the change of abiotic variables changes the composition of the macroinvertebrate community. We collected 20,079 individuals in 91 taxa, Chironomidae being the most abundant, followed by Ceratopogonidae, Oligochaeta and Leptoceridae. Point two showed higher richness and abundance, with 64 taxa and 43.55% of the total individuals. In the dry period, there was a greater input of organic matter, higher concentrations of nutrients in the water, higher rates of decomposition and increase the number of macroinvertebrates. Predator was the predominant trophic category, followed by collector and scraper. By relating the PCA axes with the NMDS, it can be seen that the macroinvertebrate community varies with the abiotic variables. There was no significant relationship between the number of shredders and decomposition rates; there significant relationship between the number of macroinvertebrates and the rate of decomposition only in point three. These results can be explained by the abandonment of the shredders of litterbags the loss of quality of the leaves after 30 ± 2 days of incubation and the highest capacity retention of leaf litter in point three. The study of litter decomposition in this region is an unpublished data, increasing the knowledge about this important process in tropical environments.