Relationship between space distribution of the benthic macroinvertebrates community and trophic state in a Neotropical reservoir (Itupararanga, Brazil)

Abstract

The purpose of this work was to verify the benthic macroinvertebrates community responses through environmental factors along a headwater tropical reservoir. Samplings were taken with a Van-Veen grab along the reservoir in littoral and profundal regions and in the headwater, next to the dam and the middle of the reservoir. Samples were taken during both wet and dry seasons. Dissolved oxygen concentrations, electric conductivity, temperature and pH near the sediment have been performed in situ, at every sampling station by using a multiprobe and Secchi disc. Total water phosphorus and chlorophyll a concentrations were analyzed to determine the trophic state index. Sediment's organic matter, total phosphorus, nitrogen concentrations and granulometric composition were measured. In order to verify which environmental variables would have more influence over the benthic macroinvertebrates community, a canonical correspondence analysis (CCA) was performed. The total number of recorded taxa was 28. Among them, the family Chironomidae (Diptera) was the richest group (19 taxa). It can be proposed that the benthic macroinvertebrates community may be influenced by environmental conditions such as nutrient and organic matter availability, as well as dissolved oxygen concentration. Macroinvertebrates are adequate bioindicators of water quality due to their sensibility to environmental changes mentioned before. Chironomus sp, Limnodrilus hoffmeisteri and Branchiura sowerbyi comprises a group that can be considered bio-indicators of eutrophic conditions. A second group can be considered as indicator of mesotrophic conditions. The presence of two or more members from that group which comprises Tanytarsini spp, Fissimentum sp, Pelomus sp and Goeldichironomus sp, like predominant taxa, may indicates mesotrophic conditions.

Spatial and temporal heterogeneity in a subtropical reservoir and their effects over the benthic macroinvertebrate community

“…The dam region is better preserved, as there is less anthropic activity in the surrounding areas (Salles et al, 2008;Beghelli et al, 2012).…”

Ecological assessment of a southeastern Brazil reservoir

“…Araú jo & Santos (2001) reported weak associations between abiotic parameters and the ichthyofauna. However, Beghelli et al (2012) observed a relationship between macroinvertebrates and the trophic state index at different sampling sites in a reservoir in Sã o Paulo state. That study indicated that the benthic macroinvertebrate assemblage responded to nutrient availability and dissolved oxygen concentration.…”

Uso do índice de estado trófico e análise rápida da comunidade de macroinvertebrados como indicadores da qualidade ambiental das águas na Bacia do Rio Jundiaí-Mirim - SP – BR

“…organismos reconhecidos como indicadores de ambientes oligotróficos e mesotróficos (Rosin et al, 2010;Beghelli et al, 2012) e a menor proporção de Chironominae vermelhos que são indicadores de ambientes impactados com pouco oxigênio no fundo (Fusari & Fonseca-Guessner, 2006). Porém, há a presença da espécie invasora Corbicula fluminea (Müller, 1774) que pode representar uma ameaça biológica à estrutura desta comunidade e do ambiente em questão (Sousa et al, 2008).…”

“…Apenas o ponto A foi classificado como em condição "razoável", indicando a presença de impactos no ambiente, mas ainda em intensidades amenas enquanto os demais pontos encontram-se em situações preocupantes refletindo provavelmente, poluição por matéria orgânica, supressão de mata ciliar ou eutrofização do ambiente (Mandaville, 2002;Fusari & Fonseca-Guessner, 2006;Beghelli et al, 2012;US-EPA, 2012).…”

“…Além disso, foram registrados valores muito elevados de densidade no ponto B, indicando acúmulo de matéria orgânica que é o alimento da maioria dos macroinvertebrados bentônicos (Beghelli et al, 2012) enquanto no ponto D, a densidade esteve anormalmente baixa, provavelmente devido à falta de condições para o estabelecimento destes organismos (sem mata ciliar e em um canal de concreto, com pouco sedimento). Ainda assim, neste último ponto, os únicos táxons presentes são reconhecidamente indicadores de ambientes impactados.…”