SEA- WATER SUPPLY IN THE TROPICS 



117 



trodes. Oxygen level may be set and 

 maintained at any desired level between O 

 and saturation. Deviations of the meas- 

 ured level from the present level will pro- 

 vide the control signal for adjusting the 

 oxygen level in the incoming water supply. 

 Oxygen will be added to or removed from 

 the water by passage through a column 

 of glass beads into which oxygen or nitro- 

 gen is metered. 



Dissolved carbon dioxide 



Measuring and control systems similar 

 to those provided for oxygen will be sup- 

 plied. Carbon dioxide will be added to or 

 removed from the sea water by trickling 

 through a glass bead column into which 

 carbon dioxide is metered or COo^free 

 air is passed. An adjustment of pH will 

 be made along with the regulation of 

 carbon dioxide. 



Turbidity control 



Measurement of turbidity will be made 

 by absorption of light as compared to a 

 neutral density filter. Filters of a wide 

 range of optical density may be inserted 

 into the reference optical path of the con- 

 trol system, and turbidity can then be 

 automatically maintained at a level of 

 equal light absorption. Increase of tur- 

 bidity can be accomplished by metering 

 in a suspension of the material under 

 study or of some natural sediment into the 

 incoming water supply, or it can be de- 

 creased by filtering. The type of material 

 to be used will depend on whetlier visual 

 effects or effects of sedimentation on bot- 

 tom organisms are being investigated. 



Sysfem for maintaining programed variations of any 

 controllable parameter 



This system will consist of a graphic 

 recorder and controller which will follow 

 a curve previously plotted on the chart 

 paper. Any desired fluctuation of a vari- 

 able (as a function of time) can be plotted 

 on the chart paper by hand. As the 

 graphic record is played back, the stylus 



is made to follow the excursions of the 

 plotted line while at the same time pro- 

 ducing a control signal which is a func- 

 tion of its lateral displacement. The 

 control signal is used to regulate the en- 

 vironmental parameter so that it follows 

 directly the preplotted graphic record. 

 The time scale may be synchronized with 

 real time if desired. Fluctuations in such 

 variables as temperature, salinity, or light 

 may be provided in a cyclic manner so that 

 tidal or diurnal cycles are simulated. 

 Noncyclic variations may be programed 

 in the same manner. 



SUMMARY 



The following problems, some of which 

 are peculiar to the tropics, have been dealt 

 with in the design of the new sea-water 

 system : 



1. Sedimentation and growth of fouling 

 organisms in the pipes by (a) filter 

 screens at intake, (b) duplication of all 

 pipelines from intake to final distribution 

 lines, (c) provisions for daily flushing of 

 all pipes, (d) continual flushing of sedi- 

 ments from settling tank, (e) final dis- 

 tribution lines and petcocks leave from 

 the upper sides of secondary supply lines, 

 and (f) use of straight runs of pipe with 

 no elbows. 



2. Air embolism in experimental ani- 

 mals, by (a) use of a gravity system of 

 sea-water distribution, and (b) avoidance 

 of temperature increases by continual 

 flushing of water from the storage tank 

 and by insulating the tank from direct 

 sunlight. 



3. Toxicity to experimental animals, 

 corrosion, and erosion, by (a) use of non- 

 toxic plastic pipe and valves, and (b) use 

 of rubber-coated pumps. 



We believe that this facility, when com- 

 pleted, will be an important addition to 

 the nation's research facilities. The in- 

 tensive planning which has resulted in the 

 final flexible design, both of the laboratory 



