M. annularis and S. siderea gave generally similar patterns in loss of 

 radioactivity. Initially, the radioactivity in the ethanol fraction 

 rose, particularly in _S. siderea , and then fell as the WH[j^OH-extractable 

 fraction rose. This took place over the first U8 hrs,, after which there 

 was a generally slow decline in activity in both corals, leaving approxi- 

 mately 33^ of the original activity after 11 days. The half life of loss 

 of activity was not constant, indicating contributions from an unknown 

 number of distinct metabolic sources. 



The initial rise in radioactivity in S. siderea after the source of 

 label had been removed, requires comment. It seems reasonable to dis- 

 count irregularity of labeling as an explanation since the rise persisted 

 over a period of k hrs. and involved some samples not taken from the edge 

 of the colony. An inherently more attractive explanation for the result 

 is that a fraction with water soluble components was lost during sampling 

 or subsequent transfer to ethanol. Cell intermediates e.g., leading to 

 lipids would fit this category. The curves show that radioactivity in 

 ethanol soluble components is transferred to ammonia soluble compounds, 

 e.g., proteins. Note that this appears to occur most obviously in the 

 hours of darkness. 



CONCLUSIONS 



Although this experiment did not provide information applicable directly 

 in estimating rates of production and turnover by corals, it demonstrated 

 the feasibility of obtaining this information, and the time scale involved, 

 when working at depths well beyond those employed in earlier studies. 

 Furthermore, the necessity for additional controls, particularly to re- 

 cover excreted products was made apparent. It will be possible to attend 

 to these deficiencies in future studies. 



REFERENCES 



Muscatine, L. and Cernichiari, E. I969. Assimilation of photo- synthetic 

 products of zooxanthellae by a reef coral. Bio. Bull., 137, 506-523. 



Ryther, J. H. 1969. Photosynthesis and fish production in the sea. 

 Science, I66, 72-76. 



Stoddart, D. R. 1969- Ecology and morphology of recent coral reefs. Biol. 

 Rev., UM, Ui+3-498. 



STANDING STOCKS OF ORGANIC CARBON AND NITROGEN IN SESSILE 



ORGANISMS ALONG A TYPICAL REEF TRANSECT 



OBJECTIVES 



Stoddart (I969) has discussed the obvious difficulties associated with 

 quantitative studies of the sessile components of coral reef communi- 



VI-254 



