41
limited growth to test many of these predictions, studies of steadystate growth limited by other macronutrients are consistent with the
predictions of the carbon-limited model.
If the thermodynamic model is of value, its predictions must be
consistent with measurements of growth in continuous culture, and the
model should suggest general mathematical relationships that can be usefully applied to descriptions of phytoplankton growth. The concluding
section of this paper will include not only a comparison of model predictions with measurements but also the derivation of a general mathematical description of steady state growth.
V. STEADY STATE GROWTH IN CULTURES
The predictions of the thermodynamic model have been compared with
measurements (by L· aws and Bannister, 1980) of the growth in continuous
culture of the marine diatom, Thalassiosira weissflogii . Cultures
were grown in either chemostats where the rates of supply of either
ammonium, nitrate, or phosphate were limiting to growth or in turbidostats where light levels were limiting .
In the chemos tats, light levels
were both constant and saturating for growth; in the turbidostats nutrient concentrations were saturating.
The results of such studies are
conveniently summarized in Figure 4, in which the specific growth rate
of the culture is plotted against the ratio of cellular chlorophyll to
carbon.
. . .
,.
...
.
'.
..
Figure 4. The specific growth rate
of Thalassiosira weissflogi i and
corresponding ratios of cellular chlorophyll and carbon. Data are from
Table 1 of Laws and Bannister (1980),
and symbols for the different limitations are 0 - nitrate, 0 - ammonium;
6 - phosphate, and 6 - 1 i ght .
It appears from this fiqure that the response of the diatoms to variations in either of the three limitins nutrients are similar and that
this response is distinct from that for light-limitations. When the
predictions of the models shown in Figures 2 and 3 are plotted accordingly, a similar pattern exists.
The conversion of light energy into cellular material can be described as merely the product of the flux of light absorbed by the
limited growth to test many of these predictions, studies of steadystate growth limited by other macronutrients are consistent with the
predictions of the carbon-limited model.
If the thermodynamic model is of value, its predictions must be
consistent with measurements of growth in continuous culture, and the
model should suggest general mathematical relationships that can be usefully applied to descriptions of phytoplankton growth. The concluding
section of this paper will include not only a comparison of model predictions with measurements but also the derivation of a general mathematical description of steady state growth.
V. STEADY STATE GROWTH IN CULTURES
The predictions of the thermodynamic model have been compared with
measurements (by L· aws and Bannister, 1980) of the growth in continuous
culture of the marine diatom, Thalassiosira weissflogii . Cultures
were grown in either chemostats where the rates of supply of either
ammonium, nitrate, or phosphate were limiting to growth or in turbidostats where light levels were limiting .
In the chemos tats, light levels
were both constant and saturating for growth; in the turbidostats nutrient concentrations were saturating.
The results of such studies are
conveniently summarized in Figure 4, in which the specific growth rate
of the culture is plotted against the ratio of cellular chlorophyll to
carbon.
. . .
,.
...
.
'.
..
Figure 4. The specific growth rate
of Thalassiosira weissflogi i and
corresponding ratios of cellular chlorophyll and carbon. Data are from
Table 1 of Laws and Bannister (1980),
and symbols for the different limitations are 0 - nitrate, 0 - ammonium;
6 - phosphate, and 6 - 1 i ght .
It appears from this fiqure that the response of the diatoms to variations in either of the three limitins nutrients are similar and that
this response is distinct from that for light-limitations. When the
predictions of the models shown in Figures 2 and 3 are plotted accordingly, a similar pattern exists.
The conversion of light energy into cellular material can be described as merely the product of the flux of light absorbed by the