resulting in a buildup of litter as increased fuel sources for destruc- 

 tive wildfires. (A. A.) 



Keywords: primary productivity, planning, ecosystems, estuaries, 

 Florida 



II-D-5 



Jones, J. A. 1968. Primary productivity by the tropical marine turtle 



grass, Thalassia testudinum Koig, and its epiphytes. Ph.D. Thesis. 



University of Miami, Coral Gables, Fla. 206 pp. (Diss. Abstr:29-3637-B) 



The measurement of primary productivity by aquatic spermatophytes 

 is complicated by environmental changes, tissue destruction, and possible 

 wound metabolism for experiments on uprooted plants, or the interactions 

 between the plant and the rest of the community for in situ experiments. 

 Three approaches to the determination of primary productivity have 

 been tested on the marine turtle grass, Thalassia testudinum , and its 

 epiphytes. One method measures production rate under nearly natural 

 community conditions. A second is used to determine the potential 

 production by an individual isolated spermatophyte. The third approach 

 investigates the contribution by the epiphytic flora. The first two 

 methods involve the polarographic determination of the change in dissolved 

 oxygen concentration due to productivity by the plants under bell jars 

 or within chambers. Differential manometry has been adapted to the 

 determination of changes in gas volume due to productivity by the 

 epiphytes. 



Gross productivity by Thalassia may reach about 1.0 ml 02/g-hr. Mean 

 respiration rate is about -0.15 ml 02/g-hr. Maximum net production is 

 about 700 ml 02/m2.hr. with a corresponding respiration rate of about 

 -100 ml Op/m^-hr. Production rates are primarily dependent upon irra- 

 diance and standing crop. Respiration rates are primarily dependent 

 upon temperature and standing crop. 



p 

 Total annual production by a dense community is about 1700 L 02/m'^, 

 900 gc/m^, or 18 kg live plant tissue per square meter. One-fourth 

 to one-third of the community metabolism may be attributable to the 

 epiphytes, which may constitute the only readily available source of 

 food to the herbivores of the community. (A. A.) 



Keywords: primary productivity, turtle grass, Florida, Thalassia 



79 



