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Communication at the NABS Annual meeting, Keystone, 2000
(161) THE EFFECT OF ENVIRONMENTAL STABILITY ON HYPORHEIC COMMUNITY STRUCTURE.
R.T. Fowler and R.G. Death. Institute of Natural Resources-Ecology, Massey University, Private bag 11-222 Palmerston North, New Zealand
Interstitial water samples were collected from two well depths (30 and 60 cm) in 8 rivers in the Cass-Craigieburn Pass region, South Island (New Zealand) during January 1998 to assess the hyporheos in streams of differing stability. Epigean taxa increased with declining environmental stability (i.e., increasing bed movement). Hyporheic water chemistry was more similar to surface water chemistry with decreasing environmental stability. Greatest diversity of both epigean and hypogean taxa occurred at intermediate levels of disturbance; however, invertebrate density declined with increasing bed movement. Less stable substrates are likely to have increased interstitial flow and reduced residence time, such that water chemistry was most like the river channel. In contrast, increasing substrate stability may reduce substrate porosity and increase contact time between solutes and substrates. Thus, the abundance of epigean taxa may decline with lower bed movement because the chemical nature of the water is least like the river channel (e.g., low DO, high temperature and high conductivity), while abundance of hypogean taxa increase with declining bed movement because these taxa are resilient to these conditions.
Presented at 4:45 PM on Tuesday, May 30, 2000 in General Community Ecology II
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