CHLOROPHYLL (MG./M.^) 



90 88 86 84 82 80 78 76 74 72 70 68 66 64 90 88 86 84 82 80 78 76 74 72 70 68 66 



PERCENT TRANSMISSION 



Figure 4. — The vertical distribution of beam transmittance and chlorophyll a in the upper 4Uto50 m. as observed at two 



stations in the northeastern tropical Pacific. 



depth of 100 m. almost all of the chlorophyll 

 fluorescence may be attributed to phaeo- 

 pigments. In local waters (i.e., Woods Hole, 

 Mass.) Yentsch and Menzel (1963) also ob- 

 served appreciable quantities of phaeo-pig- 

 ments. 



The spectrophotometric and fluorometric 

 techniques yield somewhat divergent results. 

 This discrepancy may result from the dif- 

 ference in material analyzed or from dif- 

 ferences in technique. The very different 

 results with Skeletonema costatum in the 

 papers by Patterson and Parsons (1963) and 

 Yentsch and Menzel (1963) suggest that the 

 two methods are not strictly comparable. 



Jeffrey (1961) reported the presence of 

 phaeophytin a in nature with samples con- 

 taining large amounts of decomposing cells. 



Quantitative data were not presented. Humphrey 

 (1962) mentioned that Jeffrey has also ob. 

 served chlorophyllide (from chlorophyll a) in 

 the presence of decomposing cells. McAllister 

 et al. (1961) failed to detect phaeophytin or 

 phaeophorbide compounds in their plastic -bag 

 experiment, although it is doubtful that their 

 spectrophotometric method was adequate to 

 detect phaeophytin a in small quantities. 



Apparently the quantity determined as 

 chlorophyll a by the Richards with Thompson 

 (1952) technique includes inactive chlorophyll 

 a derivatives when they are present. The 

 amount of this inactive material in sea water 

 appears to change with conditions and is 

 probably highly variable in nature with respect 

 to time, space, and depth. Since no data are 

 available on the relative aburfdance of active 



21 



