26
Ik further indicates the influence of temperature as a controlling
factor in the growth of Antarctic phytoplankton, as explained below.
B. Temperature
Temperature is commonly listed as one of the main factors,
or the main factor (Saijo and Kawashima, 1964), influencing the rate
of primary proguction in Antarctic waters. Antarctic phytoplankton
show a sharp drop in photosynthetic rates at temperatures above 100C.
Thus it would seem that these algal cells are obligate psychrophiles
since they grow well at low temperatures, and optimally at less than
Soc, but they will not grow at higher temperatures. Moreover, the
specific growth rates (~) for Antarctic phytoplankton are of the order
of 0.1 to 0.3 doubling per day in the Ross Sea (Holm-Hansen et al.,
1977) and 0.4 and 0.6 doubling per day in the southern part of the
Indian Ocean (Jacques and Minas, 1981). The highest ~ recorded (0.71)
by El-Sayed and Taguchi (1981) from the Weddell Sea is comparable to
the maximum division rate (0.75) to be expected at _2 0 C (Eppley, 1972).
However, according to Jacques (1983) this ~ still falls short of the
optimum rate derived from Arrhenius law (greater than 1 doubling per
day at SoC).
It further indicates that the low temperatures of Antarctic waters do indeed limit algal growth rates. El-Sayed and Taguchi
(1981) data thus support the hypothesis than Antarctic phytoplankton
are physiologically adapted to exhibit near maximal growth rates at low
temperatures.
Recent data from the Scotia Sea/northern Weddell Sea have also
indicated the importance of temperature as a controlling factor for
photosynthetic rates of Antarctic phytoplankton (Neori and Holm-Hansen,
1982). These authors conclude that temperature does limit primary production rates at times when light intensity is saturating the photochemical apparatus of the cell. Since the phytoplankton are saturated
by light intensity which is approximately 10-15% of that generally
incident upon the sea surface, it is apparent that temperature can be
a rate-controlling factor in the upper 10-20 m of the water column.
C. Nutrient Salts
The numerous observations on the nutrient salts in the Antarctic'waters clearly show that these salts appear to be in excess of
phytoplankton requirements. There are no data available to suggest that
phytoplankton growth in the Antarctic is limited by nutrient deficiency.
Ik further indicates the influence of temperature as a controlling
factor in the growth of Antarctic phytoplankton, as explained below.
B. Temperature
Temperature is commonly listed as one of the main factors,
or the main factor (Saijo and Kawashima, 1964), influencing the rate
of primary proguction in Antarctic waters. Antarctic phytoplankton
show a sharp drop in photosynthetic rates at temperatures above 100C.
Thus it would seem that these algal cells are obligate psychrophiles
since they grow well at low temperatures, and optimally at less than
Soc, but they will not grow at higher temperatures. Moreover, the
specific growth rates (~) for Antarctic phytoplankton are of the order
of 0.1 to 0.3 doubling per day in the Ross Sea (Holm-Hansen et al.,
1977) and 0.4 and 0.6 doubling per day in the southern part of the
Indian Ocean (Jacques and Minas, 1981). The highest ~ recorded (0.71)
by El-Sayed and Taguchi (1981) from the Weddell Sea is comparable to
the maximum division rate (0.75) to be expected at _2 0 C (Eppley, 1972).
However, according to Jacques (1983) this ~ still falls short of the
optimum rate derived from Arrhenius law (greater than 1 doubling per
day at SoC).
It further indicates that the low temperatures of Antarctic waters do indeed limit algal growth rates. El-Sayed and Taguchi
(1981) data thus support the hypothesis than Antarctic phytoplankton
are physiologically adapted to exhibit near maximal growth rates at low
temperatures.
Recent data from the Scotia Sea/northern Weddell Sea have also
indicated the importance of temperature as a controlling factor for
photosynthetic rates of Antarctic phytoplankton (Neori and Holm-Hansen,
1982). These authors conclude that temperature does limit primary production rates at times when light intensity is saturating the photochemical apparatus of the cell. Since the phytoplankton are saturated
by light intensity which is approximately 10-15% of that generally
incident upon the sea surface, it is apparent that temperature can be
a rate-controlling factor in the upper 10-20 m of the water column.
C. Nutrient Salts
The numerous observations on the nutrient salts in the Antarctic'waters clearly show that these salts appear to be in excess of
phytoplankton requirements. There are no data available to suggest that
phytoplankton growth in the Antarctic is limited by nutrient deficiency.