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

May - June 2008 288 ECOLOGY, BEHAVIOR AND BIONOMICS Application of Rapid Bioassessment Protocols (RBP) for Benthic Macroinvertebrates in Brazil: Comparison between Sampling Techniques and Mesh Sizes DANIEL F. BUSS AND ERIKA L. BORGES Lab. Avaliação e Promoção da Saúde Ambiental, IOC, FIOCRUZ. Av. Brasil, 4.365, Manguinhos, 21045-900 Rio de Janeiro, RJ; Neotropical Entomology 37(3):288-295 (2008) Aplicação de Protocolos de Bioavaliação Rápida para Macroinvertebrados Bentônicos no Brasil: Comparação entre Métodos de Coleta e entre Malhas RESUMO - Este estudo é parte do esforço para o estabelecimento de um Protocolo de Bioavaliação Rápida (PBR) utilizando macroinvertebrados bentônicos como bioindicadores da qualidade de água de riachos no Sudeste do Brasil. Foi analisada a relação custo/eficácia de procedimentos de coleta freqüentemente utilizados em PBRs, amostradores do tipo Surber e Kick-net, e de três malhas, 125, 250 e 500 μm. Foram coletados e identificados 126.815 macroinvertebrados, representando 57 famílias. As amostras coletadas com Kick-net apresentaram número de taxa e de valores do índice BMWP significativamente maiores do que as coletadas com Surber, sem um aumento significativo no esforço amostral medido em tempo despendido para análise da amostra. Não houve diferenças significativas quanto à relação custo/eficácia 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 significativas no número de taxa e em valores do índice BMWP. Assim, a malha de 500 μm foi considerada mais eficiente do que as malhas mais finas. 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, bioindicador ABSTRACT - 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 significantly higher richness and BMWP scores in relation to Surber, but no significant increase in the effort, measured by the necessary time to process samples. No significant differences were found between samplers considering the cost/effectiveness ratio. Considering mesh sizes, significantly higher abundance and time for processing samples were necessary for finer meshes, but no significant 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, bioindicator The 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 May - June 2008 Neotropical Entomology 37(3) regional biotic attributes of reference conditions (Barbour et al. 1999). Given its cost-effective principle, RBPs have been widely used in many countries to assess biological water quality and ecological health of aquatic ecosystems (Plafkin et al. 1989, Chessman 1995, AQEM 2002). Successful biological monitoring and assessment depend on rigorous quality control, starting from the design and execution of field studies to proper laboratory procedures and data analyses (Doberstein et al. 2000). Wadeable streams RBP methodologies intend to be efficient, effective, low in cost and easy to use (Resh & Jackson 1993, Resh et al. 1995), but significant differences exist between sampling techniques, forms of processing samples and metrics used. Biologists choose study sites and plan data analyses based on study objectives. However, the steps in between the collection of samples, the separation of organisms from the substrate and the level of identification, are often a product of tradition or convenience. Decisions concerning the choice of sampling device, where to take samples, whether to subsample, and how to sort samples, may greatly influence study conclusions and subsequent management considerations (Carter & Resh 2001). Many organisms have been tested in RBPs (Karr 1981, Barbour et al. 1999), and benthic macroinvertebrates are the most used group around the world (Rosenberg & Resh 1993, Chessman 1995). Therefore, it is a reasonable choice for use in the Neotropical region. However, the systematic development of RBP tools on river basins using benthic macroinvertebrates in Brazil is recent (Marques & Barbosa 2001, Buss et al. 2003, Maltchik & Callisto 2004), and very few studies dealt with testing methods in this region. This study is part of the effort to test and standardize RBP methods using macroinvertebrates as bioindicators of water quality in streams and rivers. The aims of this study were to compare the cost-effectiveness of two sampling techniques frequently used in macroinvertebrate RBPs, Surber and Kick screen net, and the cost-effectiveness of three mesh sizes, 125, 250 and 500 μm. In order to propose the application of wadeable stream RBPs in Brazil, other studies are being conducted for testing subsampling methods, taxonomic sufficiency, and the development of multimetric indices to assess biological water quality (Buss 2001, Silveira et al. 2005, Baptista et al. 2007). Material and Methods Field and laboratory procedures. The study took place in the municipality of Guapimirim, Rio de Janeiro state, one of the best preserved Atlantic Forest areas in the state. This area was an ideal place for a rigorous testing of sampling methods because of high macroinvertebrate diversity and because ecological patterns and taxonomy are well known in this region (Buss et al. 2002, 2004). Three streams were chosen for this study. The main objective was to make an intense effort to compare samples within each stream. Two stream sites (A and B) were classified as reference areas, with dense riparian vegetation (75% stream cover), (...truncated)