Chironomidae and other macroinvertebrate communities in a tropical floodplain ri ver ¬Rio Bento Gomes / MT

Abstract

Two different environments were sampled at one of the Bento Gomes river springs, a tributary of the Pantanal of Mato Grosso, located in a cerrado region at the Fazenda Fortaleza (56^°30' W and 15^°40' S). One environment (station 1) is located in an open field presenting helocrene­limnocrene characteristics, while the other (station 2) is located under a gallery forest, with limnocrene­rheocrene features. Samples were collected monthly between drought (September/95) and flooding (December/95) periods. A representative collection of the community was taken with a 125 µm mesh, covering the whole environment under a selective sampling method. Water temperature, pH and conductivity, as well as air temperature and precipitation were monitored monthly. Stations differed significantly (p ? 0,05) for depth and conductivity. The Brillouin diversity index showed a higher Chironomidae diversity in station 2. Based on taxa composition, a temporal change in community structure was observed, with an increase in diversity from drought to flooding period. Larsia was the most frequent Chironomidae genus, followed by Ablabesmyia and Genus 2 (Tanytarsini) in station 1, and Genus 2 (Tanytarsini), Tanytarsus and Nimbocera in station 2. The differences observed in macroinvertebrate and Chironomidae community structure between both stations and throughout the hydrological cycle phases probably reflect the influence of environmental variables on resource availability.