Diversidade de insetos aquáticos em riachos urbanos: a importância de fragmentos florestais

Abstract

Urban expansion is a reality in the Amazon biome, which has transformed aquatic ecosystems, with a decrease in water quality and a reduction in the diversity of organisms. Groups of species, such as aquatic insects, can indicate the biotic condition of the ecosystem through the frequency and occurrence of taxa indicators. The environmental disturbances caused by urbanization can be detrimental to the survival of some sensitive aquatic insects in Amazon rivers. The aim of our study was to evaluate the environmental condition and diversity of aquatic insects in streams in secondary forest and urban streams in the municipality of Bragança, Pará, Brazil. Data on insect groups, environmental variables and levels of disturbance (using the Habitat Integrity Index, HII) were collected between October and December 2023. A total of 423 individuals were collected, 69 in the streams of the secondary forest and 354 in the urban streams, distributed in the orders Ephemeroptera, Trichoptera, Odonata, Diptera, Coleoptera and Hemiptera. Twenty-two families were recorded in urban streams and 12 families in the secondary forest. The patterns of abundance and richness showed a decrease as the months progressed in both environments. The BergerParker dominance index in both environments showed an increase as the months went by, indicating a change between the insect communities. On the other hand, the Margalef diversity index in both environments decreased over the months. According to the levels of environmental disturbance assessed, both environments were classified as “altered” (IIH<0.70) A positive association was demonstrated between the abundance of Hydropsychidae and the variables of electrical conductivity and total dissolved solids. Environmental variables such as electrical conductivity, total dissolved solids, phosphate and dissolved oxygen are associated with variation in the composition of aquatic insect groups. Strong relationships were recorded between the distribution of Gomphidae and phosphate concentrations. Corduliidae was related to total dissolved solids and electrical conductivity. Coenagrionidae and Caenidae showed positive responses to dissolved oxygen. The study showed a greater number of aquatic insect families in the area with strong anthropogenic pressure than in the secondary forest area, possibly due to a high diversity of microhabitats. In addition, urbanization factors could be negatively affecting both environments.