ECOLOGY OF THE MURRAY ISLAND CORAL REEF. 



19 



literature of the subject. By far the most complete are those of Vaughan 

 upon the reef corals of Tortugas, Florida, and of Andros Island in the 

 Bahamas. Also, recent observations of value have been made by Guppy, 

 J. Stanley Gardiner, and Wood Jones upon corals of the Indian Ocean, and 

 a paper embodying these results has been published by Wood Jones. 



Vaughan has presented a paper upon this subject together with tables 

 in the year book of the Carnegie Institution of Washington for 1915, No. 14, 

 pp. 221-23 1. 1 According to Vaughan, Orbicella annularis, which forms large 

 compact dome-like heads upon the Florida and Bahama reefs, grows upward 

 from s to 6.8 mm. per year, while the branching Acropora palmata grows 

 upward at rates between 25 and 40 mm. per year. 



Observations upon Pacific corals are by no means so trustworthy as 

 those of Vaughan upon the Atlantic forms, for the growth period is not so 

 accurately known and the measurements were not so carefully made. How- 

 ever, Guppy 2 concludes that in the Cocos-Keeling Islands massive forms of 

 Pontes grow upward between 12.7 and 19 mm. per year, while the branching 

 Pontes {palmata?) grows about 30 mm., and certain forms of Montipora and 

 Acropora at least 100 to 125 mm. per year. Also, Sluiter, 3 states that a 

 young reef at the Black Cliff, Krakatoa, grew to a thickness of 200 mm. in 

 not more than five years, and Gardiner (in his report upon the coral reefs of 

 the Maldives and Laccadives) states that the upward growth of Perforata 

 is about 20 mm. per year, while that of the massive Astraeidae is 22 mm. and 

 of Fungidae 29 mm. per year. The general average for about 28 species of 

 corals is 25.6 mm. per year. 



The observations and estimates of growth-rate of Pacific corals are con- 

 sistent in indicating a more rapid rate than has been determined by Vaughan 

 for Atlantic corals. This may be due to errors in the less careful measure- 

 ments made in the Pacific; but their consistency inter se inclines one to sus- 

 pect that in coordination with the greater richness, both in species and indi- 

 viduals, the growth-rate of Pacific reef-corals may be more rapid than that 

 of corresponding genera in the Atlantic. In common with other ccelenterates 

 the growth-rate of corals probably depends upon the abundance of food and 

 thus a comparative study of the conditions of the supply of zooplankton in 

 the tropical Atlantic and the Pacific to the corals might throw light upon 

 the question. 



Thus in the Florida-Bahama region the corals usually grow near the 

 outer edges of extensive, shallow limestone flats, the water over which is 

 charged with precipitated calcium carbonate, which is fatal to most pelagic 

 animals. In the Pacific, however, the reef flats are usually deeper, the 

 precipitated limestone is less, and the pure ocean water, with its freight of 

 pelagic life, is more accessible to the corals than in the Atlantic. 



'Also in Journal Washington Acad. Sci., vol. 5, pp. 591-600. 

 2 Guppy, 1889, Scottish Geographical Magazine, vol. 5, pp. 573-575. 

 3 Sluiter, 1889, Natuurkundjg, Tijdschrift Nederland. Indie, vol. 49, p. 375. 



