43
Figure 5. Predicted quantum efficiency
and specific growth rate of lightlimited cells. The other pair of
curves (X) show measured quantum
efficiencies and specific growth rates
for Thalassiosi ra weissflogi i,
growing under light limitations.
Figure 5 also includes calculations of the light-limited growth
rates obtained by substituting cp (Eo) (equation 17) for cp in equation 16
and calculating ~+r for differing values of Eo and ChI/c. Values for
~ were then obtained from ~+r by application of the empirical equation
of Laws and Bannister (1980).
Equation 17 is substituted for cp in equation 16 to yield:
~+r
CPm Kcp ChI a p Eo
C(Kcp + Eo)
(18)
It is proposed that this equation provides a general description of the
steady state qrowth of phytoplankton that is consistent with the behavior
of the thermodynamic model. As a test of the validity of this equation,
we have introduced measured values of Eo' C, and ChI for light- and
nutrient-limited growth of !. weissflogii into equation 18. The predicted values of ~+r were then compared with the valu~s of growth and
respiration measured by Laws and Bannister as shown in Figure 6.
It
is evident from this figure that equation 18 both linearizes the data
shown in Figure 4 and accurately predicts the growth rate of T . weissfloqii in continuous culture.
0'
.' .
OZ
0 4
06
o.e
10
12
.,","..-cohc,.~ .. ~ f .. , 11
Figure 6. Observed and corresponding
predicted gross production for Thalassiosira
weissflogi i that are limited in growth rate
by either nutrients or light. Predicted
rates were calculated from equation 18.
Symbols for different 1 imitations are :
X - nitrate; 0 - ammonium; 6 - phosphate;
o - 1 i ght.