Chironomidae and other aquatic macroinvertebrates of a first order stream: community response after habitat fragmentation

KLEINE¹, P. & TRIVINHO–STRIXINO², S.

^1,2 Laboratório de Entomologia Aquática, Depto. de Hidrobiologia –Universidade Federal de São Carlos. Cx. Postal 676. 13.565-905, São Carlos, SP. e-mail: prikleine@yahoo.com; strixino@power.ufscar.br

ABSTRACT: The macroinvertebrate community is one component of the lotic system that best reflects the level of environmental integrity. Environmental impacts may result in the lowering of biological diversity and in the modification of functional structure of this community. Based on this premiss, in the present study was analysed the influence of habitat fragmentation resulting of damming and deforestation of a stream of first order on the benthic macrofauna. The analysis was done on three segments of the Fazzari stream (São Carlos, SP, Brazil): 1 – preserved segment, near to the headstream and protected with riparian vegetation; 2 – segment without riparian vegetation, localized downstream of two reservoirs; 3 – segment downstream of segment 2, situated in a area partially covered by riparian vegetation. The collections were done during the dry season (August to October/ 2003) with aid of a Surber collector in 10 points on each segment (5 in pools and 5 in riffles). The specimens were identified until family level, except for Chironomidae, which were separated by morfotypes. The results pointed out higher richness and diversity in segment 1; segments 2 and 3 had lower richness and diversity levels and an elevated participation of Chironomus larvae (genera with many tolerant species). Other metric of evaluations also pointed the lost of biological integrity in the stream sections above the reservoirs. The analysis of feeding groups indicated differences in the distribution of functional groups, with greater participation of shredders in the vegetated segment 1 and dominance of collectors in segments 2 and 3. Although the analysis of grouping considered all together segments 2 and 3, other metrics of evaluation seem to indicate that segment 3 presents a discrete recovery, possibly due to the presence of the riparian vegetation.

Key-words: Aquatic Macroinvertebrates, lotic systems, Chironomidae, habitat fragmentation, first order stream.