FROELICH, Jenna*; STENGER, Krista; HILL, Malcolm; KINGSLEY, Roni; University of Richmond; University of Richmond; University of Richmond; University of Richmond: UREASE AND CALCIUM CARBONATE SPICULE FORMATION IN THE OCTOCORAL LEPTOGORGIA VIRGULATA

The gorgonian, Leptogorgia virgulata<1> is a temperate, colonial cnidarian, found in the sub-tidal coastal waters of the mid-Atlantic and southeastern United States. A characteristic feature of this and other gorgonians is an abundance of calcium carbonate spicules throughout the entire colony. When organisms such as this gorgonian form these calcified structures, an acidic environment is generated which then must be adjusted or the calcium carbonate will dissociate. Numerous mechanisms are involved in the removal of acidic conditions from the calcifying environment. For example, the enzyme carbonic anhydrase has been reported to function in this manner in a several calcifying organisms. Another enzyme that may also be involved in this process is urease. We propose that urease provides two functions in L. Virgulata: 1) It provides a carbon source for the production of CaCO₃; and 2) It provides ammonia which spontaneously combines with the free H⁺ion left from the calcification process to form ammonium ions which passively diffuses out of the organism into the water. This reverses acidosis, increasing the pH, and allowing calcification to occur. In this study, immunoreactive urease protein was detected in gorgonian extracts by western blotting. Immunoreactivity appears strongest in the samples collected during the summer and fall, and weakest in samples collected in the winter. This annual pattern appears to reflect that of spicule calcification and corresponding collagenous spicule organic matrix formation. That is, organic matrix and spicule formation is greatest in the summer, drops in the winter, and initiates again in the spring. These parallel findings suggest that urease is involved in the calcification process.