ECOLOGY AND TAXONOMY OF Holimeda 



265 



however, for the revelation that rates are remarkably similar through- 

 out generic taxa, and for suggesting that rates of deposition in algae 

 and in corals are greater in the light, and therefore may be associated 

 with photosynthesis. 



Table XXVII gives Goreau's results for the species of Halimedae he 

 used and Table XXVIII for some hermatypic corals. The difference in 

 the light : dark ratios of calcium uptake between the two groups is very 



Table XXVIII. Rates of Calcium Uptake and Accretion in Hermatypic 



Corals'' 



"From Goreau (1963). Uptake in [J.gCa mgN""^ h~^, accretion in percentage increment h~^. 



apparent. Figure 87 illustrates Goreau's conclusion that there is a close 

 affinity between the members of a plant taxon in the calcium uptake 

 rate. 



Calcium is present within the Halimeda segment not only as arago- 

 nite, but also in the cytoplasm, filament wall and spaces of the segment. 

 Measurement of calcium uptake, therefore, is more than a measure of 

 rate of calcification, and the variations obtained in calcium uptake rates 

 with different labelling and washing times (Table XXIX) are partly 

 a consequence of these different locations within the plant. Rate of 

 calcium uptake also would be expected to vary with the environmental 

 conditions of the experiment, and the physiological condition of the 

 segment and plant. 



