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Importance of environmental factors on the richness and distribution of benthic macroinvertebrates in tropical headwater streams
Citation:
Ferreira, W., R. Ligeiro, D. Macedo, R. Hughes, Phil Kaufmann, L. Oliveira, AND M. Callisto. Importance of environmental factors on the richness and distribution of benthic macroinvertebrates in tropical headwater streams. Freshwater Science. The Society for Freshwater Science, Springfield, IL, 33(3):860-871, (2014).
Impact/Purpose:
The USEPA’s NARS survey designs and field methods are being applied in large basin stream surveys in countries outside of the U.S. These applications not only provide valuable tests of the NARS approaches, but generate new understandings of natural and anthropogenic controls on biota and physical habitat in streams. These understandings not only aid interpretation of the condition of streams in the regions surveyed, but also refine approaches for interpreting aquatic resource surveys elsewhere. Metrics describing the taxonomic richness of macroinvertebrates are one of the mainstays of biomonitoring in wadeable streams and rivers. Ferreira and co-authors, using USEPA NARS stream survey designs and field methods in two large basins within the Cerrado biome of Brazil, evaluated the relative importance of multiple physical and chemical habitat variables influencing (EPT richness), an aquatic macroinvertebrate metric describing the richness of Ephemeroptera, Plecoptera and Trichoptera, which are typically the more sensitive of the biota found in wadeable streams of the Brazilian savanna, as well as in other biomes. NARS physical habitat variables were more important than water quality variables in structuring EPT genera in savanna streams with catchments dominated by agriculture or pasture land uses. These results indicate that the sufficiently comprehensive landscape, disturbance and physico-chemical data should be collected in association with biotic data in order to effectively assess human impact on biodiversity and biointegrity.
Description:
It is essential to understand the interactions between local environmental factors (e.g., physical habitat and water quality) and aquatic assemblages to conserve biodiversity in tropical and subtropical headwater streams. Therefore, we evaluated the relative importance of multiple physical and chemical habitat variables influencing the richness of typically more sensitive Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages in wadeable Brazilian Cerrado (savanna) streams. To do so, we sampled macroinvertebrate assemblages and quantified physical and chemical habitat in 79 randomly selected sites in two Cerrado basins in southeastern Brazil. The environmental variables, selected by multiple regression models (MLRs) via corrected Akaike Information Criteria (AICc), contributed significantly to the variation in EPT taxa richness. The variance explained by physical habitat variables in the Upper Sao Francisco Basin (adjusted r2 = 0.53) was slightly greater than in the Upper Araguari Basin (adjusted r2 = 0.46), and both were greater than the variance explained by a combined biome model (adjusted r2 = 0.39). In our study, physical habitat variables were more important than water quality variables in structuring EPT genera in savanna streams with catchments dominated by agriculture or pasture land uses. We conclude that regional models can be improved by incorporating basin-specific information, in this way refining biological assessments and better understanding the interactions that maintain biodiversity in stream networks.