Bioindicators are species, groups of species or biological communities whose presence, quantity and distribution indicate the magnitude of environmental impacts on an aquatic ecosystem and its drainage basin (CALLISTO & GONÇALVES, 2002). Thus, using bioindicators, it is possible to carry out a complete assessment of the ecological effects caused by various sources of pollution. In this sense, this assessment becomes more efficient than immediate measurements of physical and chemical parameters, such as temperature, pH, oxygen, among others, which are commonly measured in the field and used to assess water quality. The U.S. Environmental Protection Agency (USEPA) and the European Union Directive (94C 222/06, August 10, 1994) recommend the use of bioindicators in conjunction with standardized parameters for assessing water content.
Aquatic ecosystems have been significantly altered due to multiple environmental impacts resulting from mining activities; the construction of dams and reservoirs; the straightening and detour of the natural course of rivers; the discharge of untreated domestic and industrial effluents; deforestation and inadequate land use in riparian regions and flood plains; the exploitation of fishing resources and the introduction of exotic species (GOULART & CALLISTO, 2003).
Benthic macroinvertebrates are efficient for assessing and monitoring the impacts of anthropogenic activities on continental aquatic ecosystems (CALLISTO, 2000; GOULART & CALLISTO, 2003). Among them, the larvae of aquatic insects, water worms, snails, worms and crustaceans predominate, with body sizes larger than 0.2-0.5 mm (CALLISTO, 2000). They are relatively sessile and many benthic organisms feed on organic matter produced in the water column or from marginal vegetation that falls onto the riverbed. They are important components of the diet of fish, amphibians and aquatic birds and therefore transfer the energy obtained from the dead organic matter retained in the sediment to the animals that feed on them. In this way, these organisms become good bioindicators of water quality because they are generally more permanent in the environment, as they live for weeks to a few months in the sediment. For this reason, their monitoring becomes more efficient than monitoring based solely on measuring physical and chemical parameters (LENAT & BARBOUT, 1994; ALBA-TERCEDOR, 1996).
The ideal Environmental Biomonitoring Program is one that integrates physical, chemical and biological measurements, allowing for the physical-chemical characterization of the aquatic ecosystems of a river basin and the study of the ecology of bioindicator organisms of water quality. The use of these organisms as bioindicators is based on a simple principle: subjected to adverse conditions, organisms adapt or die. Therefore, the organisms that live in a given ecosystem are adapted to its environmental conditions and should therefore reflect the level of preservation of natural conditions or the changes caused by the emission of environmental pollutants (HYNES, 1974).
Bibliographical references
ALBA – TERCEDOR, J. Macroinvertebrados acuaticos y calidad de las aguas de los rios. IV Simposio del agua en Andaluzia (SIAGA), Almeria, v. 2, p. 203-13. IBSN: 84-784, 1996.
CALLISTO, M. Macroinvertebrados bentônicos. In: Bozelli, R.L.; Esteves, F.A. & Roland, F. Lago Batata: impacto e recuperação de um ecossistema amazônico. Eds. IB-UFRJ/SBL. Rio de Janeiro, p. 139-152, 2000.
CALLISTO, M. & GONÇALVES, J.F.Jr. A vida nas águas das montanhas. Ciência Hoje, 31 (182): 68-71, 2002.
CALLISTO, Marcos; GONÇALVES JR, José Francisco; MORENO, Pablo. Invertebrados aquáticos como bioindicadores. Navegando o Rio das velhas das Minas aos Gerais, v. 1, p. 1-12, 2005.
GOULART, M.D. & CALLISTO, M. Bioindicadores de qualidade de água como ferramenta em estudos de impacto ambiental. Revista FAPAM (no prelo), 2003.
HYNES, H, B. N. Comments on taxonomy of Australian Austroperlidae and Gripopterygidae (Plecoptera). Australian Journal of Zoology. Csiro Publications, Collingwood. 1-52, Suppl. 9, 1974.
LENAT, D. R. & BARBOUT, M. T. 1994. Using benthic macroinvertebrate communitie structure for rapid, cost – effective, water quality monitoring: rapid bioassessment. In: Coeb, S. L. & Spacie, A. (eds) Biological Monitoring of aquatic systems. Lewis Publishers, Boca Ratom, Florida; p. 187-215.