THE PHYSIOLOGY OF SKELETON FORMATION IN CORALS. III. CALCIFICATION RATE AS A FUNCTION OF COLONY WEIGHT AND TOTAL NITROGEN CONTENT IN THE REEF CORAL MANICINA AREOLATA (LINNAEUS)

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Abstract
A study was made of the relation of colony weight to the total N content and calcification rate in M. areolata, using colonies weighing between 0.047 to 148.5 g. The ratio of the surface area, as measured by the total N, and volume, as determined by the weight of the coral, remained nearly constant over the range of colony sizes tested. The specific calcification rate of the smallest colonies was about 76 times greater than that observed in the biggest specimens in the series. The slopes of the plotted curves indicate that the growth rate decays as an exponential function of the size, i.e. the age of the coral, which can be described by a relationship of type X=Ae- [image] where X=total colony size, weight or N content, and Y=the amount of C deposited per unit weight of N. The growth rate of the largest colonies was somewhat greater than expected, and there is reason to believe that the relationship given above may hold only for colonies weighing less than about 100 g. Similar but much less marked decreases of the specific calcification rate with size were observed in M. areolata colonies which lacked zooxanthellae. It is suggested that, although the zooxanthellae are powerful stimulants to the calcification reaction, they are not as such responsible for the decay of the growth rate with increasing size and/or age. The causes for the reduction in specific calcification rates with age are not understood, but may be due to an effect of senescence.