New Zealand Journal of Marine and Freshwater Research abstracts
Seasonal changes in factors controlling phytoplankton growth
in Beatrix Bay, New Zealand
M. M. GIBBS
W. N. VANT
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11-115
Hamilton, New Zealand
Abstract Phytoplankton biomass and growth rates were measured
in Beatrix Bay, Marlborough Sounds, during 1994-95. In spring and summer,
nitrate and chlorophyll a concentrations in the mixed layer were low
(typically < 1 mg N m-3 and < 1 to 3 mg Chl. a
m-3, respectively), and phytoplankton growth rates were moderate
(average 0.3 d-1). Growth rates increased several-fold in response
to the experimental addition of inorganic N (but not to inorganic phosphorus).
Higher nitrate concentrations were found below the pycnocline. During autumn
and winter, nitrate concentrations in the mixed layer were high (up to 60 mg
m-3), but phytoplankton growth rates were lower than in summer
(average 0.2 d-1), and did not respond to added nutrients.
Chlorophyll a concentrations, however, were highest during the winter
(typically 3-6 mg m-3). Even so, low light levels meant integral
photosynthesis per unit chlorophyll a was low in winter. Phytoplankton
growth appears to be controlled by the availability of nitrogen in summer and
by light in winter.
Keywords phytoplankton; algal growth; photosynthesis;
nutrients; light; aquaculture; Pelorus Sound
New Zealand Journal of Marine and Freshwater Research, 1997, Vol. 31:
237-248
0028-8330/97/3102-0237 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (1009K); (scanned from paper original: notes about this process)
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