BIOCHEMICAL STUDIES OF A CORAL REEF ECOSYSTEM 



J. S. Bunt, K. E. Cooksey, M.A. Heeb, C. C, Lee and B. Taylor 



Rosenstiel School of Marine and Atmospheric Science 



University of Miami 



Rickenb acker Causeway 



Miami, Florida 331^9 



ABSTRACT 



This study had several distinct objectives. In situ 

 acetylene reduction assays were run with a wide range of 

 benthic algae and sediment materials for the detection of 

 possible nitrogen fixation. Results were uniformly 

 negative and extensive search failed to disclose obvious 

 existence of heterocystous blue-green algae. A second 

 series of assays based on phytoplankton rich in Trichodesmium , 

 however, gave strong indications of acetylene reduction. A 

 typical area of reef was selected for a description of bio- 

 mass distribution. This phase of the work required systematic 

 sampling and photography along a marked transect with sub- 

 sequent analysis of the corals and other materials recovered. 

 Measurements were made of carbon- lU fixation in situ by 

 typical reef corals. 



ASSAYS FOR MARINE NITROGEN FIXATION IN THE VIRCIN ISLAMDS 



BENTHIC ALGAE 



OBJECTIVE 



Bunt _et _al. (1970) have adapted the acetylene reduction technique (Stewart, 

 Fitzgerald and Burris, I967) of detecting nitrogen fixation for submarine 

 application. We report here the results of its use during Mission 12-50 

 of TEKTITE II. 



EQUIPMENT AND PROCEDURE 



The method itself is described in Bunt et al. (1970)- It need be added 

 only that syringes containing argon and acetylene were prepared for use at 

 the surface and lowered to the aquanauts as required. Algal samples were 

 collected in the general vicinity of the habitat both over the reef and 

 the algal flats. Incubations were made at 20 m for 3 hrs. between III5 

 and IU15 hrs. local time. Gas samples, returned to the surface by 

 syringes, were transferred immediately to serum- stoppered, water- filled 

 tubes, taking care to leave several cms. of water in each tube and to 

 keep the tubes inverted. All samples were returned within two days to 

 Miami for gas chromatographic analysis at these laboratories. Prior trials 

 had shown losses of ethylene to be negligible under these conditions. 



VI-247 



