Benthic macroinvertebrate communities in nonregulated and regulated waters of the clearwater river, Idaho, U.S.A.

Abstract

Benthic macroinvertebrates were examined over a two-year period in nonregulated, regulated, and semiregulated reaches of the Clearwater River in northern Idaho. Macroinvertebrate communities in the nonregulated reach above Dworshak Reservoir were taxonomically diverse at all stations. In contrast, the macroinvertebrate community in the regulated reach of the North Fork of the Clearwater River (NFCR) was severely altered with high macroinvertebrate abundance and low taxa richness (2 to 8 taxa). Orthoclad chironomids dominated this reach composing between 68 and 99 per cent of total benthic invertebrate numbers. The mayfly Ephemerella infrequens was the only other macroinvertebrate to be abundant in the regulated reach. The major factors contributing to the simplified macroinvertebrate community are reduced habitat diversity, fluctuating water levels, altered thermal regime, and possibly an altered food supply. The effects of the dam were mitigated in the semiregulated Mainstem of the Clearwater River (MSCR) due to the merger of a nonregulated fork entering 2.5 km downstream from the dam. The macroinvertebrate community in the semiregulated MSCR was more complex than the regulated reach with a community structure resembling that found above the reservoir. a W c s J F M A M J J A S O N D MONTHFigure 4. Cumulative annual degree-days at the nonregulated NFCR and the regulated NFCR for 1983

Consequences of dam construction upstream of the Upper Paraná River floodplain (Brazil): a temporal analysis of the Chironomidae community over an eight-year period

“…In some cases, the regulation of flow facilitates the dominance of some morphospecies (Munn and Brusven, 1991), which was probably the reason that the following species became dominant (Kownacki index) in the Paraná River and then in the Ivinhema River immediately after the second filling stage of the Porto Primavera reservoir: Polypedilum (Tripodura) sp.1, Lopescladius sp.1, Tanytarsus sp.1, Coelotanypus sp.1, Ablabesmyia (Karelia) sp.1, Djalmabatista sp.2 and Axarus sp.1.…”

Flow preferences of larval Chironomidae (Diptera) in Tongariro River, New Zealand

“…In addition, the relatively stable flows at the two lower sites on Tongariro River may favour some taxa. In regulated rivers elsewhere, constant baseflows have been shown to provide suitable habitat for species of Orthocladiinae, Diamesinae, and Tanytarsini, possibly because of increases in fine paniculate food supplies (Armitage et al 1987;Petts 1988;Munn & Brusven 1991).…”

Chironomidae (Diptera) community structure in two subsystems with different states of conservation in a floodplain of southern Brazil

“…The lowest diversity values and the highest number of dominant groups in the Paraná subsystem are probably also related to the impacts caused by damming. According to Munn and Brusven (1991) and Takao et al (2008) the macroinvertebrate assemblage downstream the branches, providing great quantity of microhabitats. In addition, areas with riparian vegetation, such as the Ipoitã Channel, maintain higher diversity of Chironomidae than deforested areas (HenriquesOliveira et al, 1999).…”