New Zealand Journal of Marine and Freshwater Research abstracts
Phytoplankton photosynthesis and growth in contrasting regions of Manukau Harbour, New Zealand
W. N. VANT R. G. BUDD
NIWA-Ecosystems
National Institute of Water & Atmospheric
Research Ltd P.O. Box 11-115 Hamilton, New Zealand
Abstract
Contrasting environments for phytoplankton growth are found in Manukau Harbour. Nutrient levels are higher in parts of the inner harbour than elsewhere; and cells spend less time in aphotic waters there than in the outer harbour. Phytoplankton photosynthesis and growth in these regions were determined during 1991-92. Average levels of biomass in the inner regions were 2-4 times those in the outer regions, where chlorophyll
a averaged 2-3 mg m~
3. However, the euphotic zones were about twice as deep in the outer regions, so average rates of gross photosynthesis were reasonably similar overall (344-557 mg C m~
2 d"
1). Respiration losses were greatest in the outer harbour, so net photosynthesis was lower there. During a late-summer diatom bloom in the inner harbour, peak values of chlorophyll
a and gross photosynthesis were 66 mg m~
3 and 4100 mg C m"
2 d"
1, respectively. A simple equation involving biomass, euphotic depth, and incident light accounted for most of the variability in euphotic zone photosynthesis. Average growth rates varied across the harbour: from about 0.4 d"
1 in the inner harbour, to less than half this in the outer regions where the aphotic zone was deeper.
Keywords photosynthesis; phytoplankton; algal growth; light; nutrients; estuary; Manukau Harbour
M93003
Received 8 January 1993; accepted 19 April 1993
New Zealand Journal of Marine and Freshwater Research, 1993: Vol. 27: The Royal Society of New Zealand 1993
Received 8 January 1993; accepted 19 April 1993
PDF file of entire paper: medium quality (1017K); (scanned from paper original: notes about this process)
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