Macroinvertebrados como bioindicadores de qualidade de água do Açude Santo Anastácio, Fortaleza/CE

Abstract

Bioindicators are organisms capable of attesting with their presence or absence, and their autoecology, the condition of an ecosystem. In aquatic environments, macroinvertebrates show great potential as bioindicators, since they have wide spatial distribution (making it possible to compare them in different environments), with the level of tolerance to pollutants among taxonomic orders is quite variable. Biotic indices help to read the trophic state of the ecosystem, providing a picture of the aquatic biota, identifying the components most susceptible to the expected impacts and defining the best indicator of water quality. The Açude Santo Anastácio (ASA), located in the city of Fortaleza (Ceará) is currently considered a hypereutrophic environment due to the high input of organic matter and sewage it receives. This study identified the families of macroinvertebrates that occur in the ASA and their relationship as indicators of water quality from biotic indices. Monthly macroinvertebrate collections were conducted between the months of October 2018 to March 2019. Macroinvertebrate specimens associated with the aquatic macrophyte Eichhornia crassipes (aguapé) were collected using 1 m² quadrants and in the bottom substrate with a 3-liter capacity Ekman dredge. 202 organisms were identified, divided into 23 families (Atyidae, Belostomatidae, Chaoboridae, Chironomidae, Coccinellidae, Curculionidae, Dytiscidae, Euconulidae, Glossiphoniidae, Gomphidae, Gryllidae, Hydrophilidae, Membracidae, Mesoveliidae, Noteridae, Phalacridae, Physidae, Planorbirdae, Pleidae, Salticidae, Stratiomyidae, Syrphidae, Thiaridae). The most abundant families were: Chironomidae (34.15%), Thiaridae (22.77%), Hydrophilidae (13.46%), Syrphidae (4.45%), Glossiphoniidae (3.36%). The most abundant classes were Insecta (64.35%) and Gastropoda (29.70%), both classified as indicators of low water quality. The BMWP-ASPT and IBF indices classified the ASA with probable moderate organic contamination and low water quality, respectively, corroborating with results found in the literature on the state of degradation of the water body. The EPT/Chironomidae index classified the water quality as very bad, due to the abundance of Chironomidae and absence of representatives of the Ephemeroptera, Plecoptera e Tricoptera.