VENRICK, McGOWAN, and MANTYLA: PHOTOSYNTHETIC CHLOROPHYLL 



-ARIES I NOV -DEC 1970 



KIUUERO 31 MARCH 1969- 



FlGURE 2. — Vertical sections of chlorophyll a concentrations in the Pacific Ocean; vertical exaggeration 5020. 



be confluent with that discussed by Anderson 

 (1969) , the Central, and the Equatorial environ- 

 ments. 



The east-west section indicates that the max- 

 imum layer is well developed over most of the 

 middle latitudes of the South Pacific. The max- 

 imum layer in the South Central Gyre tends to 

 be deeper, and the chlorophyll concentrations 

 throughout the water column tend to be lower 

 than in corresponding areas of the North Pacific. 

 The greatest depth so far observed by us was 

 at lat 20°09'S, long 118°18'W, during December 

 (ARIES I Expedition) where a layer containing 

 0.05 mg/m^ occurred between 200 and 245 m 

 depth; chlorophyll values at the surface were 

 less than 0.01 mg/m^ 



Portions of all three sections have been re- 

 peated by different expeditions. The depth and 

 concentration of chlorophyll in the maximum 

 layer vary somewhat, but the general features 

 remain the same. In 1969, the Ocean Research 

 Institute, University of Tokyo, ran a transect 

 along long 155°W (Ocean Research Institute, 

 University of Tokyo, 1970) . The results of their 

 chlorophyll measurements compare well with 

 ours. 



VERTICAL DISTRIBUTION 



We have supplemented our discrete, quantita- 

 tive chlorophyll samples with in vivo profiles of 

 fluorescence which provide continuous, but qual- 

 itative pictures of the fine scale structure of the 

 maximum layer (Figure 3) . Although the major 



RELATIVE FLUORESCENCE 



Stpt 21, 1968 

 aT'OtfH 155'50'W 



March 19, 1971 

 24'36'S I59*00'W 



Stpt 19. 1968 

 26'58'N IS5* 24'W 



Figure 3. — Continuous vertical profiles of in vivo fluor- 

 escence of chlorophyll, a) a simple maximum layer in 

 the North Central Pacific; surface chlorophyll concen- 

 tration 0.02 mg/m^; b) a simple maximum layer in 

 the South Central Pacific; surface chlorophyll concen- 

 tration 0.01 mg/m^; c) a double maximum layer in 

 the North Central Pacific; surface chlorophyll concen- 

 tration 0.02 mg/m3. 



45 



