Application of rapid bioassessment protocols (RBP) for benthic macroinvertebrates in Brazil: comparison between sampling techniques and mesh sizes

Abstract

As amostras coletadas com Kick-net apresentaram número de taxa e de valores do índice BMWP signifi cativamente maiores do que as coletadas com Surber, sem um aumento signifi cativo no esforço amostral medido em tempo despendido para análise da amostra. Não houve diferenças signifi cativas quanto à relação custo/efi cácia entre os coletores. Quanto ao tamanho da malha, em 125 μm e 250 μm foram encontradas maiores abundância de macroinvertebrados e necessário mais tempo para processar as amostras, no entanto sem produzir diferenças signifi cativas no número de taxa e em valores do índice BMWP. Assim, a malha de 500 μm foi considerada mais efi ciente do que as malhas mais fi nas. Portanto, recomenda-se o uso de coletores do tipo kick usando uma malha de 500μm, para PBRs ao nível taxonômico de família em rios de características similares às deste estudo no Brasil.PALAVRAS-CHAVE: Avaliação ambiental, inseto aquático, ecologia de rios, biomonitoramento, bioindicadorABSTRACT -This study is part of the effort to test and to establish Rapid Bioassessment Protocols (RBP) using benthic macroinvertebrates as indicators of the water quality of wadeable streams in south-east Brazil. We compared the cost-effectiveness of sampling devices frequently used in RBPs, Surber and Kick-net samplers, and of three mesh sizes (125, 250 and 500 μm). A total of 126,815 benthic macroinvertebrates were collected, representing 57 families. Samples collected with Kick method had signifi cantly higher richness and BMWP scores in relation to Surber, but no signifi cant increase in the effort, measured by the necessary time to process samples. No signifi cant differences were found between samplers considering the cost/effectiveness ratio. Considering mesh sizes, signifi cantly higher abundance and time for processing samples were necessary for fi ner meshes, but no signifi cant difference were found considering taxa richness or BMWP scores. As a consequence, the 500 μm mesh had better cost/effectiveness ratios. Therefore, we support the use of a kick-net with a mesh size of 500 μm for macroinvertebrate sampling in RBPs using family level in streams of similar characteristics in Brazil.KEY WORDS: Environmental assessment, aquatic insect, freshwater ecology, biomonitoring, bioindicatorThe original Rapid Bioassessment Protocols (RBPs) were designed as inexpensive screening tools for determining if a stream is supporting or not supporting a designated aquatic life use. However, RBP tools can also be applied to other program areas, like characterizing the existence and severity of impairment to the water resource; helping to identify sources and causes of impairment; evaluating the effectiveness of control actions and restoration activities; supporting use attainability studies and cumulative impact assessments and characterizing

Structure and dynamics of the community of periphytic algae in a subtropical reservoir (state of São Paulo, Brazil)

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