New Zealand Journal of Marine and Freshwater Research abstracts
Variations in benthic fauna between differing lake outlet types in New
Zealand
JON S. HARDING
Department of Zoology
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
Abstract Physico-chemical conditions and macroinvertebrate
faunas of 20 South Island lake outlets were investigated in summer-early autumn
of 1990-94. Four outlet types were recognised: unregulated alpine, unregulated
mid/low elevation, regulated hypolimnetic and regulated epilimnetic outlets.
Alpine outlet waters had significantly lower (
P < 0.05) alkalinities
and conductivities (6-12mg l
-1 CaCO3 and 13-45
uS
cm
-1) than all other outlets (11-36mg l
-1 CaCO3 and
36-93
uS cm
-1), whereas pH values were similar among outlet
types. Substrate size was significantly greater in modified epilimnetic than
natural mid/low elevation outlets (
P < 0.01). Total number of taxa
and invertebrate densities were significantly lower in alpine and hypolimnetic
outlets than natural mid/low elevation outlets (
P < 0.05, and
P < 0.01 respectively), and distinct differences were observed in the
relative abundances of major taxonomic groups. Alpine streams were dominated by
the mayflies
Deleatidium (Leptophlebiidae), and
Nesameletus
(Siphlonuridae), the gripopterygid stonefly
Zelandoperla decorata and
predatory hydrobiosid caddisflies; molluscs were absent, and filter-feeding
hydropsychid caddisflies rare. In contrast, the hypolimnetic outlets were
dominated by filter-feeding hydropsychids (87-93% of the fauna), and no
stoneflies were found. Epilimnetic and unregulated mid/low elevation outlets
had similar communities, however invertebrate densities were significantly
lower in regulated surface release outlets. Altitude, outlet width, velocity,
conductivity, and percentage of the catchment in forest, were all implicated as
factors explaining differences in community composition.
Keywords Lake outlets; benthic invertebrates; streams;
regulated rivers; DECORANA; New Zealand
New Zealand Journal of Marine and Freshwater Research, 1994: Vol. 28:
417-427
0028-8330/94/2804-0417 $2.50/0 (c) The Royal Society of New Zealand
1994
PDF file of entire paper: medium quality (717K); (scanned from paper original: notes about this process)
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