generally in the range 1500-3500 g. carbon/m2/year . By comparison, 

 rich upwelling waters are believed to produce only around 300 g 

 carbon/m2/year (Ryther, I969) • The question whether photo synthetic 

 carbon fixation by the zooxanthellae of the coral exceeds respiratory 

 losses by the symbiotic association is still at issue and may depend on 

 location. This study was undertaken to explore the field and subsequent 

 laboratory problems of measuring carbon fixation and turnover in individual 

 reef corals J:!! situ . Working in 20 m of water out of the TEKTITE II 

 habitat made it possible for two divers to complete repetitive sampling 

 operations without intervening periods spent in decompression. The experi- 

 ment, however, required support from research divers stationed at the 

 surface . 



EQUIPMENT, PROCEDURES AKD EXPERIMENTAL MATERIAL 



Of the many species of coral available, Monastrea annularis and 

 Siderastrea siderea were selected because of their convenient size and 

 form, the fact that they fragment easily and evenly and do not exude 

 mucoid substances excessively when handled. These two species are 

 attractive also because they are major Caribbean reef builders. 



Selected coral heads were dislodged gently from the substrate and labeled 

 with the technique described by Muscatine and Cernichiara (1969) using 

 60|iCi NaHl^C03 and a 3-hour exposure period in the late morning at I8 m 

 when bottom illumination was maximal. Sampling, according to a predeter- 

 mined schedule and continuing for 11 days was initiated immediately 

 following removal of the coral heads from the plastic bags. The pattern 

 of sampling, which required hammer and chisel, is shown in Figure 1. 



Concerned at the possibility that labeling over the surface of the coral 

 heads may not have been uniform, a separate coral head was examined in 

 detail by taking a series of samples immediately following exposure to 

 l^c as shown in Figure 2. In this case, the specimen was dissected after 

 return to the surfa^ce. 



At each sampling on the bottom, triplicate pieces of coral were sent to 

 the surface in small plastic bags and there transferred within 5 minutes 

 to glass jars of 70fo ethanol. The material was returned to Miami for 

 extraction and determination of radioactivity. 



The 70^ ethanol used as preservative served also as the first extract- 

 ing liquid, a second aliquot of ethanol being used after the first was 

 decanted. Combined, the volume of the extracts was measured and sub- 

 samples counted at infinite thinness in thin end window counters. The 

 radioactivity in the ethanol extract was not lost by gentle heating with 

 dilute HCl. 



The alcohol- treated coral was then extracted twice with boiling 6N-NH1|0H 

 and the radioactivity counted. A third ammonia extract and the remaining 

 skeletal parts were negligibly radioactive. 



VI-250 



