Effects of turbidity on calcification rate,protein concentration and the free amino acid pool of the coral Acropora cervicornis

Calcification rate in the coral Acropora cervicornis was reduced significantly when exposed for 24 h to 100-ppm kaolin, but was unchanged in corals exposed to 50-ppm kaolin. Calcification rate returned to control levels during a 48-h recovery period. Most free amino acids (FAA) in the FAA pool decreased significantly in corals exposed to 100-ppm kaolin, but were unchanged in corals exposed to 50-ppm kaolin. After a 48-h recovery period, the FAA pool remained considerably below control levels in the 100-ppm exposed corals and dropped below control levels in the 50-ppm exposed corals. Calcification rate dropped less and later during the exposure period in the growing tip than in sections further down the stalk. The reduction in FAA pool size was considerably larger in the growing tip than further down the stalk. Soluble protein concentration remained unchanged during both exposure and recovery. The data are consistent with the interpretation that turbidity not only causes a decrease in photosynthetic rate and the synthesis of small molecules, but also causes a large increase in the utilization of stored organic molecules for such metabolically costly processes as mucus production and sediment removal.