Table 1. — Integrated Daily Values of the Ratio of 

 Total Photosynthesis to Respiration 



Acropora cervicornis .87 



Montastrea cavernosa .89 



Manicina areolata, variety danaei .79 



Table 2.-- Maximum Photosynthesis to Respiration Ratios 



Manicina areolata, variety danaei 2.84 



Mussa arrgulosa 1.15 



Montastrea cavernosa 2.90 



Acropora cervicornis 2.76 



Manicina areolata, variety areolata 2.91 



Colpophyllia natans 1.87 



Siderastrea siderea 2.15 



The oxygen consumed by areas of sandy bottom between coral reefs was measured 

 by the same technique as that used on coral heads. Such areas were found to 

 use an average of 1.35 x 10"-^ ml/cm'^/hr during daylight. 



The oxygen pressure 10 feet off the bottom at the TEKTITE II habitat reached a 

 maximum of 153 mm Hg p02 shortly after noon and a minimum of about 118 mm Hg 

 p02 shortly before sunrise. Among the coral heads (not in deep holes) on the 

 nearby reef, values as low as 100 mm Hg p02 were recorded in the predawn hours. 



Photographs and direct observation showed that the extension and activity of 

 coral polyps is related to light. The "nighttime position" (tentacles extended 

 and active) is assumed shortly after sunset, and the polyps retract promptly at 

 the first light of dawn. The polyps likewise assume their nighttime position 

 during periods of artificially imposed darkness (Figure 3). This made it impos- 

 sible by the present methods to determine whether the true respiratory rate of 

 the system was the same during periods of illumination as in darkness. 



Light intensity measurements throughout the water column from the surface to 65 

 feet were made by a surface diver. A GE Type 213 light meter with a variety of 

 neutral density and colored filters was used to determine the penetration of the 

 various colors of light. Approximately 337o of the total surface light pene- 

 trated to 65 feet. Light of wavelengths near 460 m/i» was absorbed least (20%); 

 above this, the longer wavelength, the greater the absorption. These data 

 closely resemble those of Jerlou (1951) for Caribbean water. 



CONCLUSIONS 



At depths at least up to 65 feet, where the maximum measured light intensity 

 was found to be 2500 foot candles, the integrated 24-hour photosynthesis almost 

 equals the comparable value of respiration in several coral-algal associations 



VI-244 



