7993

• UCREFRP Catalog Number: 7993
• Author: Mabey, L. W.
• Title: Planktonic and Benthic Microcrustaceans from Floodplain and River Habitats of the Ouray Refuge on the Green, River, Utah - Master's Thesis.
• USFW Year: 1993.
• USFW - Doc Type: Brigham Young University,
• Copyright Material: NO

Discussion
The study site is 259 km downstream of Flaming Gorge Dam on the Green
River. Studies on other rivers by Herlong and Mallin (1985) and Sandlund (1982)
have shown that up to 45 % of plankton aze removed within 200 m downstream of the
dam and 76 % aze removed within 2.2 km. They still report influences at 3.4 km from
the dam. Reservoir plankton may exist in reduced numbers for several hundred
kilometers on lazge rivers (Wazd 1975). However, at great distances the river
plankton may be dominated by plankton from source areas along the river (Repsys
and Rogers 1982). The study site is 259 km downstream of the Flaming Gorge Dam
and reservoir plankton is not believed to influence the microcrustacean densities of the
communities, at the Ouray Refuge azea of the Green River.
n i'
Many studies of invertebrate drift address microcrustaceans secondarily (eg.
Clifford 1972, Benke et al. 1991) and their data aze not directly comparable with this
study. This is a result of too lazge of mesh size or failure to identify species. Other
studies have specifically assessed microcrustaceans densities (Holden and Green 1960,
Hanf 1982, Saunders and Lewis 1988x, 1988b, 1989; Grawbowski and Heibert 1989).
Backwater. This study reported plankton densities of 1,450-7,131/m3 for the
Ouray backwater and 63,353/m3 and for Intersection Wash. The benthic densities at
the Ouray backwater were 6x greater per squaze meter than for the plankton in
August and equal in July, but no existing density estimates aze available for
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