Figure 3. Top view of car on vertical railway tracks of 

 the tower used to make vertical casts for water turbidity 

 and temperature and to pump water for plankton. 



A. Hydrophotometer (alpha meter) 



B. Pressure transducer (for depth) 



C. Thermistor (for temperature sensing) 



D. Underwater pump 



E. Pump intake 



INSTRUMENTS 



The car on the western or seaward track contains the 

 sea instruments (fig. 3) used for the study. ^ They include 

 a hydrophotometer, temperature sensor, pressure trans- 

 ducer, and a submersible pump with its underwater intake. 



The instrument used for measuring turbidity was a one- 

 half-meter hydrophotometer (fig. 3-A), designed and con- 

 structed by the Scripps Institution of Oceanography Visibility 



