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1995] MACROINVERTEBRATES OF THE GREEN RIVER 223 ! ( been reached by other investigators (Beckett et al. 1983, Statzner and Higler 1986). Grabowski and Hiebert (1989) concluded that benthic macroinvertebrate densities in backwaters of the Green River were higher than those of the river channel. Our data suggest that the seasonally inundated wetland and ephemeral side channel are also valuable habi- tats and have the potential to contribute sub- stantial biomass to the Green River system. Oligochaete and chironomid densities report- ed in our study are comparable to other lotic systems (Koehn and Frank 1980, Pinder 1980, Grzybkowska 1989, Grzybkowska and Witczak 1990, Palmer 1990). High densities of nema- todes and ceratopogonids imply that these groups may be very important in the overall energetics of the Green River system, Both should be studied more intensely. The overall dynamics of these communities is undoubtedly associated with seasonal changes in flow as well as year-to-year variability in annual discharge. This study, while describing a backwater, river site, side channel, and floodplain wetland over a short time interval, does not allow a full assessment of either annual or spatial variabil- ity, It is clear that some sort of successional colonization of various habitats occurs; for instance, floodplain wetlands are maximum in extent during highest spring-early summer flows, but their faunal development lags peak flooding. Backwaters do not exist during high flows, but as floodplains diminish with reced- ing water levels, backwater habitats develop. Again their faunal assemblages tend to lag be- hind the emergence of recognized backwaters. While we documented what appears to be seasonal succession within habitat type, such changes should not be assumed the norm. Until a detailed study is undertaken for the Green River or Colorado River system with replicate habitats over at least a full year period, our observations must be considered tentative, Further, annual discharge can vary tremen- dously from year to year, depending upon fac- tors such as drought cycles and their link with EI Nino dynamics in the Pacific. Thus, what is seen in one year may not be representative of all years. Such factors introduce additional variables that should be considered when attempting to understand the dynamics of the benthos of the Green River. ,,, .\ LITERATURE CITED ADAMEK, Z" AND I. SUKOP. 1992, Invertebrate communi- ties of former southern Moravian floodplains (Czecho- slovakia) and impacts of regulation, Regulated Rivers: Research and Management 7: 181-192, BECKEIT, D, C., C. R. BINGHAM, AND L. G. SANDERS. 1983, Benthic macroinvertebrates of selected habitats of the lower Mississippi River, Journal of Freshwater Ecology 2: 247-261. BERG, M, B" AND R. 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