EPPLEY: PHYTOPLANKTON AND TEMPERATURE 



results are reviewed also by Steemann Nielsen 

 (1960). Few of these earlier works included 

 chlorophyll a measurements, however, and as- 

 similation numbers are not reported. 



Ichimura (1967) found a close relation be- 

 tween temperature and assimilation number for 

 a station well within Tokyo Bay, but not at a 

 station in deeper water. Nutrient limitation 

 was postulated for the outer station. 



Some of the values for assimilation number 

 and its variation with temperature which can be 

 conveniently summarized are provided in Table 

 6. One might have hoped, by comparison of the 

 data with values expected from Figure 9, to 

 check up on the quality of one's colleagues' work 

 and to find some reported values outside the 

 bounds of reasonable expectation. Happily, only 

 one of the papers reviewed gave unrealistically 

 high assimilation numbers and these were not 

 repeated in subsequent studies by that author. 



IMPLICATIONS FOR 



SIMULATION MODELS OF 



PHYTOPLANKTON PRODUCTION 



As pointed out by Patten (1968) and others, 

 mathematical models are usually designed to be 

 accurate or alternatively, realistic, but seldom 

 are both. It can be seen from the preceding 

 discussion that attempts to compute photosyn- 

 thetic rates from temperature would generally 

 be inaccurate, and unrealistic as well, unless 

 radiant energy and concentrations of essential 

 nutrients were also considered. In the past, 

 models of photosynthesis have often included a 

 term for the maximum rate of photosynthesis 

 at light saturation which is widely acknowledged 

 to be temperature-dependent. In Steele's (1962) 

 model Pmax is a constant and is expressed in units 

 "carbon assimilation rate per unit plant carbon" 



Table 6. — Assimilation numbers measured in different ocean regions in comparison with 

 maximum expected values taken from Figure 9. A similar table is given by Saijo and 

 Ichimura (1962) for pelagic and coastal seawaters and lakes. 



■> Assumed temperature. 



Sources: (1) Saijo and Kawashima, 1964; El-Sayed and Mandelli, 1965; Mandelli and Burkholder, 1966; Home 

 et al. 1969; Bunt and Lee, 1970; (2) Biological station, Nanoimo (1970. Biological, chemicol and physical data 

 First Canadian Trans-Pacific Oceonographic Cruise March to May 1969. Fish. Res. Board Can., Manuscr. Rep. 1080, 

 92 p). (3) Steemann Nielsen and Hansen, 1959, for light-saturated rate; (5) Lorenzen, 1968, average over the 

 euphotic zone; (7) Barber and Ryther, 1969, average over the euphotic zone; (8) Sournia, 1968; (9) Malone, '971a. 

 Values designated by "a" are for nanoplankton, "b" values for netplankton; (10) Burkholder, Burkholder, and 

 Almodovar, 1967; (11) Ryther and Menzel, 1965b, average for euphotic zone. 



1079 



