New Zealand Journal of Marine and Freshwater Research abstracts
Phytoplankton biomass and productivity in two oligotrophic lakes
of short hydraulic residence time
MARC SCHALLENBERG
CAROLYN W. BURNS*
Department of Zoology
University of Otago
P. O. Box 56
Dunedin, New Zealand
Abstract Phytoplankton biomass and productivity at two sites
in the newly impounded Lake Dunstan and, upriver, in Lake Wakatipu (Frankton
Arm) showed ranges throughout 1 year of 0.2-2.0 mg chlorophyll
a
m
-3 and 0.9-6.0 mg C m
-3 h
-1 (maximum rate of
carbon fixation). Peaks in phytoplankton abundance occurred in spring and
summer in both lakes, but relationships of biomass and productivity vs light
and nutrients differed between the lakes. In Lake Dunstan, P-vs-I parameters
indicated that phytoplankton were photo-acclimated to prevailing light
conditions. In the Frankton Arm, P-vs-I parameters indicated that phytoplankton
were poorly adapted to light conditions. Phytoplankton biomass and productivity
were only depressed at the shortest observed hydraulic residence times (< 3
days). Phytoplankton biomass and productivity in Lake Dunstan were predicted
from dissolved and particulate nitrogen concentrations and mean mixed-layer
light intensity. Annual mean chlorophyll
a level was predicted
satisfactorily using a published empirical model based on total phosphorus and
inorganic suspended solids; a published deterministic model developed for
reservoirs was tested and did not predict chlorophyll
a concentrations
accurately. The results are discussed in the context of the paradigm of trophic
upsurge which is commonly observed in newly impounded reservoirs.
Keywords primary production; phytoplankton; hydraulic
residence time; reservoir; chlorophyll a
New Zealand Journal of Marine and Freshwater Research, 1997: Vol. 31:
119-134
0028-8330/97/3101-0119 $2.50/0 (c) The Royal Society of New Zealand
PDF file of entire paper: medium quality (1457K); (scanned from paper original: notes about this process)
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