Efeitos da alteração ambiental causada pela urbanização na cidade de Manaus (AM) sobre comunidades de adultos de libélulas (Insecta: Odonata)

Abstract

The accelerated growth of human population has caused major environmental disturbances. Because of its greater fragility, aquatic systems have suffered the worst impacts, causing the loss of many species. One of the main ways of measuring these disturbances is the use of bioindicator organisms. Adults of Odonata are considered good "thermometer" of the environment and its species have been used to assess the quality of the environment. Given this scenario, the objective of this study was to evaluate the effect of changing the environmental integrity of the assembly of adult Odonata in streams in Manaus, testing their potential as bioindicators of environmental quality. For this we tested the hypothesis that the environmental integrity would have positive effect on the wealth of Zygoptera and Anisoptera contrast to the wealth being negatively affected, because of the ecophysiological differences between the suborders. Samples were collected in 30 streams, 11 in degraded sites, preserved in 10 and nine intermediaries. The environmental integrity of each site was estimated by the Index of Physical Integrity Environmental modified for the urban area. Our hypothesis was supported, since presented Zygoptera positive relationship with integrity while Anisoptera negative. Based on the ordination analysis, species were separated from those preserved environments changed and degraded environments. Of a total of 60 species, nine were were considered indicative of the quality of the environmental and characterized four groups of locations (changed + degraded). Seven species (Perislestes attenuatus, Epipleoneura manauensis, Heteragrion sp. 2, Psaironeura tenuissima, Chalcopteryx rutilans, Hetaerina moribunda, Argia sp. 2) were indicative of preserved environments, two of disturbed environments (Orthemis discolor, Acanthagrion cuyabae) and featured four disturbed habitats and degraded (Argia bicellulata, Erythrodiplax basalis, Argia sp. 1, Erythrodiplax fusca). Also significant differences were found between environmental variables of the three types of environments (preserved, modified and degraded). The index of physical integrity of the environment was a good classifier of the conditions of local streams. The assembly of adult Odonata community was an important indicator of the quality of environments in the studied area. Thus, changes in species composition can be used to indicate changes in the integrity of the environment and measure the intensity of impact on the system, assisting in decision making for environmental conservation.