FISHERY BULLETIN: VOL. 70, NO. 4 



photosjTithesis and diminish the potential pro- 

 duction of phytoplankton. Nevertheless, earlier 

 reviewers have been able to generalize on sev- 

 eral aspects of the relation between phytoplank- 

 ton growth and temperature (see especially 

 Tailing, 1957; Steemann Nielsen, 1960; Ichi- 

 mura and Aruga, 1964; Yentsch and Lee, 1966; 

 Ichimura, 1968). Culture experiments have re- 

 v^ealed that clones of a species isolated from cold 

 or warm seas may differ in their optimum tem- 

 perature for growth (Braarud, 1961; Hulburt 

 and Guillard, 1968). 



VARIATION IN SPECIFIC GROWTH 



RATE ifji) WITH TEMPERATURE IN 



LABORATORY CULTURES OF 



UNICELLULAR ALGAE 



Much of the available data on the specific 

 growth rates of algae in culture have been as- 

 sembled by Hoogenhout and Amesz (1965). 

 Growth rates for marine phytoplankton fall in 

 the same range of values as those for freshwater 

 algae, and there are no obvious distinctions be- 

 tween marine and freshwater unicellular algae 

 rt'ith respect to the variation of specific growth 

 rate (/x) with temperature. Hence data for 

 algae from the two media will not be segregated. 



Specific gro\\i;h rate is defined as the rate of 

 increase of cell substance per unit cell substance 

 i/N dN/dt — [x. Since dN/dt depends upon the 

 rate of metabolic processes, one expects some 

 temperature variation of ix if conditions are 

 otherwise favorable for growth (i.e., if light and 

 nutrient supply are not growth-rate limiting). 

 This variation can be seen in Figure 1. Data 

 3f Figure 1 were selected from Hoogenhout and 

 Amesz (1965) as representing, as nearly as pos- 

 sible, growth rates measured under conditions 

 such that temperature would be rate limiting. 

 Figure 1 shows much variation in /.i among spe- 

 cies at a given temperature. Most of this re- 

 sults from differences in cell size (Williams, 

 1964; Eppley and Sloan, 1966; Werner, 1970) 

 and in the concentration of photosynthetic pig- 

 ments within the cells of the different species 

 (Eppley and Sloan, 1966). 



It has been mechanically impossible to iden- 

 tify each of the points on the Figure by species 



(approximately 130 species or clones were in- 

 cluded, some for several temperatures). No 

 doubt, by further literature search, the entire 

 area beneath the line of maximum expected 

 growth rate could be filled in. It is perhaps 

 surprising and a tribute to the quality of the 

 measurements from many laboratories that only 

 three of nearly 200 values were rejected as being 

 unrealistically high. Inclusion of these three 

 spurious values would only be an embarrassment 

 to the authors rather than a critique of the va- 

 lidity of the line of maximum expected growth 

 rate presented. 



Not plotted in Figure 1 are values of yu, for 

 Chlamydomonas mundana photoassimilating ac- 

 etate (Eppley and Macias R., 1962), Chlorella 

 pyrenoidosa 7-11-05 for which fx was computed 

 for increase in cell substance uncoupled from cell 

 division (Sorokin and Krauss, 1962), or for the 

 photosynthetic bacteria listed by Hoogenhout 

 and Amesz (1965). Values for these slightly 

 exceed the line of maximum expected /x. Figure 

 1 is limited to algae growing photoautotrophic- 

 ally with carbon dioxide and water. 



Two general trends are noted in Figure 1: 

 (1) There is a gradual and exponential increase 

 in /x with temperature up to about 40°C. Tem- 

 perature data above 40°C, obtained with thermo- 

 philic, blue-green algae show no further increase 

 in IX (Castenholz, 1969) . Such temperatures are 

 outside the range encountered in the ocean and 

 will not be further discussed. (2) Values of fx 

 below 40°C seem to fall within an envelope and 

 it is possible to draw a smooth curve, i.e., a line 

 of maximum expected value, to describe the up- 

 per limit of IX to be expected at a given temper- 

 ature. An approximate equation for this line is: 



logio fx = 0.0275T — 0.070 



(1) 



where T is temperature in degrees Celsius. 



Equation (1) gives a Qio for growth rate of 

 1.88, slightly lower than expected from the Qio 

 for photosynthesis measured in natural waters 

 (Tailing, 1955, gives Qio = 2.3; Williams and 

 Murdoch, 1966, give Qio = 2.25 ; Ichimura, 1968, 

 gives Qio = 2.1) or the Qio for growth rate of 

 laboratory cultures suggested earlier (Eppley 

 and Sloan, 1966, give Q,o = 2.3). 



1064 



