34 



PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



John S. Bruce,' Government meteorologist, the average air temperature at 

 2 p. m. during December 1914, was 35°C. 



Corals were placed on the hot sand beach in glass aquaria, the water 

 within which was heated slowly by being exposed to the sun's rays, or over a 

 spirit lamp.- Three or four hours were required to raise the temperature to the 

 highest point, after which the coral was replaced in the ocean and observed on 

 the following day to determine whether it survived or not. The results are 

 recorded in table 6. 



Table 6. — Upper temperature-limits which Ma'er Island corals cati survive. 



It appears that Seriatopora hystrix, Acropora palifera, and Eiiphyllia 

 glabrescens are killed below 37° C, and these are all corals of the outer parts 

 of the reef-flat and do not flourish within 500 feet of the shore. On the other 

 hand, Coeloseris mayeri Vaughan, Goniastrea pectinata, and the various forms 

 of Porites are resistant forms, most individuals having death temperatures 

 of 37° C. and higher, although occasionally an individual colony dies at about 

 36°, but this is quite exceptional and these species are the only corals which 

 flourish within 500 feet of the shore. 



It seems, then, that the water within 550 feet of the shore becomes too 

 hot for certain corals^ and this factor alone may possibly suffice to account 

 for these corals being confined to the seaward parts of the reef-flat. It is 

 interesting to record that these Pacific corals are not more resistant to high 

 temperature than are the corresponding genera of the Florida reefs. ^ 



At Thursday Island a death temperature due to cold for several species 

 of corals was determined with the results shown in table 7. 



'Mr. John Stewart Bruce states in a letter that the mean shade temperature of the air under a large tree 

 near the shore on the northwest side of Maer Island averaged 31.1° C. in December 1913 and 31.6° C. in both 

 January and February 1914. In 1914 the average maximum temperature ranged from 35° in December to 28.3^ 

 in July and August. 



^The author has always been mindful of the time-factor in these temperature studies (Crozier, 1916, to 

 the contrary) and the sea-water was heated at the rate of 2° C. per hour, as was also done in the study of the 

 temperature range of Florida Corals, and thus the Australian observations are comparable with those made in 

 Florida (see p. 20, Carnegie Inst. Wash. Pub. No. 183, 1914). 



"The critical temperature is that at which the corals lose their ability to capture or retain food, and we find 

 that this in Mirandra areulata, Acropora muricala, and Siderastrfa radiant of the .Atlantic ranges from 1.5° to 3° C. 

 below their death temperatures for heat. 



*See Mayer, 1914, Papers from the Tortugas Laboratory of the Carnegie Institution, vol. 6, p. 19, table 6; 

 Carnegie Inst. Wash. Pub. No. 183. 



