|
<br />00i)728
<br />
<br />Freshwater Biology (1995) 33,439--454
<br />
<br />The ordination of benthic invertebrate communities
<br />in the South Platte River Basin in relation to
<br />environmental factors
<br />
<br />C,M, TATE AND J,S, HEINY
<br />U,S, Geological Survey, Waler Resources Division, Box 25046, MS 415, Denver Federal Cenler, Denver, Colorado, 80225-
<br />0046, U,SA
<br />
<br />L Spatial patterns of benthic-invertebrate communities were examined in the 62 900 km2
<br />South Platte River Basin in Colorado, Nebraska and Wyoming, U.S,A., to determine
<br />major environmental factors associated with invertebrate distribution, Stable substrates
<br />were sampled semiquantitatively for invertebrates from 27 July to 7 August 1992, at
<br />twenty-one sites, Data on physical and chemical variables were collected concurrently at
<br />each site,
<br />2_ Four site groups were identified using detrended correspondence analysis (DCA), one
<br />in the mountains and three in the plains (braided channels, tributaries near the
<br />confluence with the main stem, and sites affected by effluent from wastewater-treatment
<br />plants), DCA axis 1 separated sites into the two major ecoregions (Southern Rocky
<br />Mountains and Western High Plains), and regression of DCA axis 1 with environmental
<br />variables indicated significant relationships primarily with slope, water temperature,
<br />specific conductance, and concentrations of organic nitrogen + ammonia and total
<br />phosphorus in surface water, Regression of DCA axis 2 with environmental variables
<br />indicated significant relationships with channel width and concentrations of
<br />nitrate + nitrite in surface water.
<br />3, Invertebrate community composition and structure varied between ecoregions with
<br />greater number of taxa and number of insect families in mountain streams than in
<br />plains streams, Within an ecoregion, land use affected the invertebrate community_
<br />4, Factors affecting invertebrate community distribution in stream ecosystems are scale
<br />dependent.
<br />
<br />~'
<br />
<br />SUMMARY
<br />
<br />r
<br />
<br />Introduction
<br />
<br />This study was conducted as a part of the U,S,
<br />Geological Survey's National Water Quality Assess-
<br />ment (NAWQA) Program which uses an integrated
<br />approach (physical, chemical and biological) to assess
<br />water quality on a basin-wide scale (Gurtz, 1994)_ A
<br />goal of the South Platte River NAWQA study is to
<br />provide a basin-wide assessment of the distribution
<br />of stream communities and examine how biological
<br />communities can be used to indicate conditions of
<br />water quality in the basin,
<br />A first step in understanding how invertebrate
<br />communities are related to water quality is to identify
<br />
<br />\
<br />
<br />@ 1995 Blackwell Science Ltd
<br />
<br />I
<br />,
<br />~
<br />
<br />i
<br />,
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />
<br />.~
<br />
<br />the primary chemical and physical variables affecting
<br />invertebrate communities within a basin. Stream com-
<br />munities are affected by many factors such as water
<br />chemistry (Meyer et ai" 1988) and the stream's physical
<br />characteristics (Resh & Rosenberg, 1984), Natural vari-
<br />ation in invertebrate communities also occurs on many
<br />spatial scales (microhabitat to regional; Naiman el ai"~
<br />1987; Minshall, 1988), Physical factors that affect
<br />stream macroinvertebrate communities include sub-
<br />strate (Minshall, 1984; Richards, Host & Arthur, 1993),
<br />flow regime (Poff & Ward, 1989), geomorphology
<br />(Huryn & Wallace 1987; Statzner, Gore, & Resh, 1988)
<br />
<br />439
<br />
|