retained in slots slightly below my right hand in the picture. A num- 

 ber of these bottles may be attached to the wire and tripped by mes- 

 sengers. Routinely, 4 to 5 samples are filtered at a time in the 

 shipboard laboratory. After the sannples are filtered they may be: 

 (1) used for pigment analysis, (2) measured to determine their dry 

 weight or some other biochemical paranneter, (3) examined by spe- 

 cial microtechniques, or (4) identified and individually counted on 

 the filter. 



In connection with studies 

 of phytoplankton, biological 

 oceanographer s are generally 

 interested in light penetration. 

 The SUBMARINE PHOTO- 

 'METER (fig. 18.4) is a Weston 

 photoelectric cell enclosed in 

 a watertight housing which is 

 lowered on a two-conductor 

 cable. The amount of light 

 detected by the Weston cell is 

 read on a microamnneter . 

 Such a unit has many advan- 

 tages with regard to simplicity. 

 However, it is becoming in- 

 creasingly apparent that we 

 need better measurements 

 which nnay be interpreted di- 

 rectly as energy. We have con- 

 sidered using pyrheliometer s 

 with special watertight housings; 

 however, further improvements 

 are desperately needed to give 

 the necessary accuracy and 

 sensitivity required for studies 

 of photosynthesis in the oceans. 



18.4 



FIGURE 



SUBMARINE 



PHOTOMETER 



202 



