| Abstract: | Calcification in Bossiella orbigniana (Corallinaceae) is characterized by a series of features which, vary according to the age of the segment (intergeniculum). From the youngest segment at the branch tip to older, more basal segments: (1) weight and degree of mineralization increase, while rate of weight gain decreases; (2) rate and stability of calcium-45 labeling decrease; (3) effect of light on calcium-45 labeling rate decreases, while effect of light on stability of label increases; however, for all segments, calcium-45 labeling is more rapid and more stable in the light than in the dark; (4) rate of calcium-45 labeling in killed controls decreases. Comparative studies with the tropical coralline alga Amphiroa yielded similar results. Characteristics of the gradients in calcification and effect of light in these coralline algae are very similar to those found, in a reef-building coral containing symbiotic algae, and the data suggest that organic products of photosynthesis may be of general importance to calcification. |
