New Zealand Journal of Marine and Freshwater Research abstracts
Physico-chemical parameters and invertebrate faunas of three lake inflows and outlets in Westland, New Zealand
JON S.HARDING
Department of Zoology
University of Canterbury
Private Bag, Christchurch, New Zealand
Abstract
Selected physico-chemical factors and the composition of faunas in inflow and outlet streams of three South Westland lakes (Kaniere, Mapourika, and Wahapo) were investigated from December 1988 to January 1990. Three sampling sites were used in each river system, the first 1 km above the inlet, another immediately below the lake, and the third 1-5 km further downstream. Dissolved organic carbon concentrations, alkalinity, and conductivity were only slightly influenced by the presence of a lake. Summer and winter water temperatures were elevated at lake outlets, but generally declined again downstream. Substrate size, stability, and homogeneity were also greater at artificial lake outlets:. Invertebrate taxonomic richness was lowest at lake outlets, intermediate in inlets streams, and greatest at downstream sites. Inflow stream faunas were dominated by
Deleatidium (Ephemeroptera: Leptophlebiidae), whereas lake outlets were dominated by Hydropsychidae, Simuliidae, and Mollusca; downstream Simuliidae, Chironomidae, and Hydropsychidae remained dominant and plecopteran taxa increased. Species of Coleoptera, Ephemeroptera, and Plecoptera were poorly represented at lake outlets but numerous at inlet and downstream sites. Substrate heterogeneity and stability, mean depth, water velocity, and water temperature were implicated as important physical environmental factors affecting community composition in lake outlets.
Keywords benthic invertebrates; lake outlets; regulated rivers; New Zealand
M91020
Received 6 May 1991; accepted 13 September 1991
New Zealand Journal of Marine and Freshwater Research, 1992, Vol. 26:The Royal Society of New Zealand 1992
Received 6 May 1991; accepted 13 September 1991
PDF file of entire paper: medium quality (657K); (scanned from paper original: notes about this process)
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