Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 65 



months it was not uncommon in shallow water to find more plankton near the bottom 

 than anywhere else ". They also found that during the spring outburst the phyto- 

 plankton caused such a great reduction in submarine illumination that the compensa- 

 tion point (or depth) was at times raised to 5 m or less. 



The sudden drop from spring growth, May 1 1th to the summer minimum, June 8th, 

 is seen in Fig. 3. The May readings were very high due to the abundance o^ Phaeocystis 

 globosa. Two filtrations were necessary because the disks became clogged, so ordinary 

 filter paper was first used and then the special membrane. Each of these was extracted 

 twice. The later cruises show the gradual growth near the thermoclinc, building up to 

 the autumn maximum, with a peculiar outburst at 25 mon August 10th of 31 -5 mg m\ 

 This outburst must have occurred in a region where light intensity allows photosyn- 

 thesis to take place and its occurrence at only this depth is probably due to the absence 

 of sufficient nutrient salts in the upper 15 m. 



The results for surface and bottom chlorophyll throughout the year are seen in 

 Fig. 4 with a surface maximum in September and April and a bottom maximum in 



SEPT 



1952 



APL I MAY 

 1953 



rnmg^.rf ' The\?a «mp™tuT«\ surface, above, and for .he bo..on, ,70 n„ ,us, below ,hc 



° ■ top line or the trame. 



D 



