CHLOROPHYLL a (/ng/ L) 

 4 8 12 



T 



UJ 

 Q 



CHLOROPHYLL a (/xg/L) 

 4 8 12 



T 



201- 



CHLOROPHYLL a (^g/L) 

 4 8 12 



e 5 



F 10 



^ 15 

 20 



3/18/71 

 1-2300 



T 



1 



IxJ 

 Q 



CHLOROPHYLL a (fig/L) 



4 8 12 



— r 



3/19/71 

 U 0400 



10 



15 



20"- 



T 



T 



CHLOROPHYLL a (yu.g/L) 

 4 8 12 



201- 



FiGURE 1.— Profiles of the concentration of chlorophyll o based upon fluorescence profiles. The upper layer of Gymnodinium splendens at 

 1230 h was concentrated at 6 m; by 1845 it had moved to 8 m and reached 15 m by 2300. Movement upward commenced at 0200 reaching 

 10 m by 0720. The lower layer remained relatively close to the bottom during this time. 



around 0600, this movement may originate from a 

 biological clock rather than from a phototactic 

 response. These observations partially conflict 

 with laboratory studies of phototaxis in G. splen- 

 dens (Forward 1974). He found that not only was 

 the cell strongly phototactic but that the strength 

 of the response was subject to a circadian rhythm, 

 being strongest at the end of the entrained dark 

 period. 



By assuming that G. splendens dominated the 

 production as well as the standing crop of phy- 

 toplankton in Coyote Bay, we obtain information 

 on the steady state doubling time for the species. 

 Water samples were collected from four depths, 0, 

 5, 10, and 18 m, inoculated with NaH^^COsi, and 

 incubated from sunrise to sunset in situ. Primary 

 production was then determined from rates of 

 light-induced incorporation of '^C into particles 

 removed by filtration. The water samples were al- 

 so analyzed for concentrations of chlorophyll a and 

 adenosine triphosphate (ATP). By multiplying the 

 concentration of ATP by 250, we obtained an es- 

 timate of "living-carbon" (Holm-Hansen and 

 Booth 1966); this estimate allowed a crude deter- 

 mination of doubling time it^ from the steady-state 

 equation: 



h = 



In 2 C-ln2 



where jLi is the specific growth rate and equal to the 

 rate of carbon assimilation, AC/A^, divided by C, 

 the concentration of cell carbon. On this basis, the 

 doubling time for G. splendens at 0, 5, 10, and 18 m 

 was 2.3, 2.6, 2.7, and 62 days, respectively (Table 1). 

 These estimates of doubling time for a natural 

 population of G. splendens may be compared with 

 a maximal doubling time of 1.6 days for cells 

 grown in the laboratory (Thomas et al. 1973). We 

 also note that our estimates of the chlorophyll a 

 concentration per cell yielded a value of 

 approximately 100 pg/cell, typical for laboratory 

 cultures (Bailey 1974). 



Table l.-Production, chlorophyll a, ATP, and doubling time for 

 a Gymnodinium splendens bloom in Coyote Bay, Gulf of 

 California. 



/* 



AC/A« 



Gymnodinium splendens in 

 the Southern California Bight 



A second bloom of G. splendens was observed in 

 March 1974, along the southern coast of California, 



676 



