A test of the assumptions and predictions of recent microalgal growth models with the marine phytoplankter Pavlova lutheri

Abstract

The marine phytoplankter Pavlova lutheri was grown in both batch and continuous culture under various conditions of light and nitrate limitation in order to examine the accuracy of certain assumptions and predictions of microalgal growth models. The N : C ratio of the cells was found to be uniquely related to their relative growth rate. There was no unique relationship, however, between Chl a : C ratios and relative growth rate. Optical absorption coefficients normalized to Chl a were negatively correlated with relative growth rate at a fixed irradiance and positively correlated with irradiance at a fixed relative growth rate when light intensity was varied with neutral-density filters. Quantum yields were positively correlated with relative growth rate at a fixed irradiance and negatively correlated with irradiance at a fixed relative growth rate. Certain parameters or combinations of parameters which appear in nutrient-saturated growth models were found to be either independent of relative growth rate at a fixed irradiance or uniquely correlated with relative growth rate. This discovery facilitates extension of nutrient-saturated growth models to nutrientlimited conditions.

Absorption, fluorescence, and quantum yield for growth in nitrogen‐limited Dunaliella tertiolecta

“…Although we have not measured respiration in this study, it is unlikely that increased respiration relative to growth could account for all of the decrease in 4, observed at low cc. For N-limited growth of Pavlova Zutheri, Chalup and Laws (1990) found a more than twofold increase in &, with p and also demonstrated an increase in &, with decreased irradiance at the same dilution rate. For N limitation of Isochrysis galbana at a single u-radiance, Herzig and Falkowski (1989) observed a range in 4, similar-to our observations and additionally found that variability in tiph was 85% of that for 4,.…”

“…Although aph*(X) can vary under steady state N-limited growth, Kiefer and Mitchell (1983) hypothesized that there should be no effect on &. Recent studies of phytoplankton in N-limited continuous culture have shown significant variability in both +,*(A) -and &,, (Chalup and Laws 1990;Herzig and Falk:owski 1989). Before the effects of physiological variability on bio-optical modeling of primary production can be evaluated, a more complete characterization of this variability and its sources is necessary.…”

An empirical model of the phytoplankton chlorophyll : carbon ratio‐the conversion factor between productivity and growth rate

“…Our approach differs from that of Geider (1987) by including an explicit connection between nutrient-limited growth rate and Chl : C. Our method is built from theoretical guidelines provided by the mechanistic models describing the links between algal growth and biochemical composition (e.g. Laws and Bannister 1980;Kiefer and Mitchell 1983;Laws and Chalup 1990). Our analysis is of results from 12 published studies that included measurements of growth rate and chemical composition of unialgal cultures grown under defined conditions of light, temperature, and nutrient delivery (Table 1).…”

“…First, there seems to be a lower limit to the Chl : C ratio, on the order of 0.003 mg Chl a (mg C)-l. Second, for fixed combinations of light and temperature, Chl : C is positively and linearly related to h' (Laws and Bannister 1980;Sakshaug et al 1989;Chalup and Laws 1990). Third, the linear relation between Chl : C and CL' varies as a function of the light condition under which cultures are grown; the comprehensive experiments of Sakshaug et al (1989) with Skeletonema costatum suggest that the slope of the relation between Chl : C and p' decreases nonlinearly with daily light exposure.…”

“…These data were converted to units [mg C (mg Chl a d)-'1 using reported values of the photosynthetic quotient where necessary. In other cases the investigators reported parameters of photosynthesis-irradiance functions based on either 14C uptake rates (Chalup and Laws 1990) or leastsquares fit of growth rates to a model similar to Eq. 3 (Sakshaug et al 1989).…”