You are here:
Development of a Benthic Macroinvertebrate Multimetric Index (MMI) for Neotropical Savanna Headwater Streams
Citation:
Macedo, D., R. Hughes, W. Ferreira, K. Firmiano, D. Silva, R. Ligeiro, Phil Kaufmann, AND M. Callisto. Development of a Benthic Macroinvertebrate Multimetric Index (MMI) for Neotropical Savanna Headwater Streams. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 64:132-141, (2016).
Impact/Purpose:
Applications and adaptations the USEPA’s National Aquatic Resource Survey (NARS) designs, field methods, and approaches for assessing ecological condition have been applied in state and basin stream surveys throughout the U.S., and also 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. Results from applications in Brazil, for example, not only aid interpretation of the condition of Brazilian streams, but also refine approaches for interpreting aquatic resource surveys in the U.S. and elsewhere. Macroinvertebrate Multimetric Indices (MMI’s) describing the biointegrity of assemblages of benthic macroinvertebrates are one of the mainstays of biomonitoring in wadeable streams and rivers. In this manuscript, the authors have applied NARS approaches in a large basin draining into a hydropower reservoir in the Neotropical Savanna of Brazil. Currently, the Neotropical Savanna is one of the most threatened biomes in the world, suffering from replacement of natural vegetation with crops, pastures, and urbanization Furthermore, most Brazilian hydropower facilities are located in this biome, which increases the exploitation of such ecosystem services as fisheries production, water supply, and recreation. Anthropogenic pressures in catchments export excess sediment and other pollutants downstream, threatening the operation and service life of reservoirs. Therefore, the MMI and IDI can be used in a broader sense to aid conservation of the Neotropical Savanna biome by measuring the effectiveness of reservoir basin rehabilitation and mitigation projects, as well as assessing and monitoring the effects of continued agricultural conversion and urbanization. The authors developed and compared four candidate MMI based on benthic macroinvertebrate assemblages Those MMI were built from landscape-adjusted and unadjusted biological metrics as well as two alternative ways of choosing metrics. The alternative MMI performances were tested by comparing their precision to distinguish least-disturbed areas, responsiveness to discriminate least- and most-disturbed areas, and sensitivity to anthropogenic pressures at catchment and local scales. The best performing MMI employed statistical criteria for identifying least- and most-disturbed sites, calibrating for natural landscape variability, and use of non-redundant metrics. Interestingly, two of the NARS stream condition indicators (riparian vegetation cover complexity and relative bed stability), were the variables that were most strongly associated with the MMI. The manuscript is a good evaluation of the various approaches and indicators that have been employed in NARS and elsewhere, and its process is a model for environmental assessment of water resources elsewhere in Brazil and in other nations.
Description:
Assessing the ecological impacts of anthropogenic pressures is a key task in environmental management. Multimetric indices (MMIs), based on aquatic assemblage responses to anthropogenic pressures, have been used increasingly throughout the world. The MMI approach is a low-cost, rapid field method that produces an aquatic condition index that responds precisely to anthropogenic pressures, making it useful for conservation and environmental management. We developed four candidate MMIs based on benthic macroinvertebrate assemblages sampled at 40 randomly selected sites to assess the environmental condition of streams upstream of a hydroelectric power plant in the Brazilian Neotropical Savanna biome. Those MMIs were built from landscape-adjusted and unadjusted biological metrics as well as two alternative ways of choosing metrics. The alternative MMIs performances were tested by comparing their precision to distinguish least-disturbed areas, responsiveness to discriminate least- and most-disturbed areas, and sensitivity to anthropogenic pressures at catchment and local scales. The best performing MMI had landscape-adjusted metrics and was produced through use of principal component analysis for metric selection. It included 4 metrics: Ephemeroptera richness, average tolerance score per taxon, percentage of predator individuals, and percentage of Odonata individuals adjusted by elevation. This index discriminated well the anthropogenic pressures at local- and catchment-scales, and at both scales simultaneously, as indicated by an integrated disturbance index. Our methodological development included statistical criteria for identifying least- and most-disturbed sites, calibrating for natural landscape variability, and use of non-redundant metrics. Therefore, we expect it will provide a model for environmental assessment of water resources elsewhere in Brazil and in other nations.
