New Zealand Journal of Marine and Freshwater Research abstracts
Shade effects on stream periphyton and invertebrates:
an experiment in streamside channels
JOHN M. QUINN
A. BRYCE COOPER
MORAG J. STROUD
GREGORY P. BURRELL
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11 115
Hamilton, New Zealand
Abstract The effects of shade on periphyton and invertebrates
were investigated by comparisons in 12 replicate channels beside a pasture
stream where shade cloth reduced the photosynthetically available radiation
(PAR) by 0, 60, 90, and 98%. Periphytic productivity decreased with increasing
shade. Periphyton chlorophyll a was consistently low
(< 30 mg m-2) under 98 and 90% shade and usually low at
60% shade, whereas blooms were common during summer in the unshaded channels.
More periphytic taxa occurred in the open than shaded channels and the relative
concentration of the photo-protective pigment beta-carotene decreased with
increasing shade. Nitrate uptake rates by periphyton, measured in separate
chamber studies, decreased progressively as shade increased from 60% through
90% to 98%, and were more strongly correlated with gross primary productivity
than periphyton chlorophyll a and particulate carbon levels. Total
invertebrate and chironomid densities declined significantly as shade increased
from 60 to 90% and invertebrate taxa richness declined markedly between 90 and
98% shade. Most collector-browsing invertebrates (other than chironomids) had
similar densities under 0-90% shade and only declined at 98%. This suggests a
weak coupling of these invertebrates with local periphyton production and also
suggests that energy derived from up-stream sources may be their most important
food in these pastoral streams.
Keywords riparian; photosynthesis; carbon; photopigments,
nitrogen; phosphorus
New Zealand Journal of Marine and Freshwater Research, 1997, Vol. 31:
665-683
0028-8330/97/3105-0665 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (1527K); (scanned from paper original: notes about this process)
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