Experimental Ecology of the Temperate Scleractinian Coral Astrangia danae . 1. Partition of Respiration, Photosynthesis and Calcification Between Host and Symbionts

Calcification, photosynthesis and respiration of the scleractinian coral A. danae were calculated from the changes in total alkalinity, pH, calculated total CO sub(2), and oxygen concentration produced by colonies incubated in glass jars. A correction for changes in ammonia, nitrate and nitrite was taken into account and the method evaluated. The fluxes of oxygen and CO sub(2) were highly correlated (r = 0.99). The statistical error of alkalinity determinations was less than 10% of the changes observed in the slowest calcifying samples. Metabolism of polyparium alone was estimated by difference after removal of tissue and reincubation of bare corallum. Zooxanthellae concentration in the polyps was obtained from cell counts made on homogenates of polyp tissue. The calculated photosynthetic rate of the zooxanthellae in vivo was 25 mu mol O sub(2) (10 super(8) cell) super(-1) h super(-1) at a light intensity of 120 mu Ein m super(-2) s super(-1). In corals having 0.5 x 10 super(9) zooxanthellae/dm super(2) of colony area up to 8% of the total photosynthesis was attributed to the corallum microcosm. The symbiosis appears to provide a growth advantage even to fed corals, under the conditions of these experiments.