J. Exp. Mar. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Biol. Ecol., 1984,Vol. 15, pp. 217-232 Elsevier 217 JEM 222 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA CORAL CALCIFICATION RATES BY THE BUOYANT WEIGHT TECHNIQUE: EFFECTS OF ALIZARIN STAINING’ RICHARD E. DODGE Nova University Oceanographic Center. 8000 N. Ocean Dr.. Dania, FL 33004, U.S.A. and SHEILA C. WYERS, H. R. FRITH, ANTHONY H. KNAP, S. R. SMITH, C. B. COOK and T.D. SLEETER Bermuda Biological Station for Research, St. George’s W est l-15. Bermuda Abstract: Thebuoyant weight method has been used in a laboratory experiment over an 18-day period to assess effects of alizarin staining on the calcification rate of the hermatypic coral Diploria strigosa (Dana). Exposure of corals to a concentration of 10 mgjl alizarin for 24 h in a flow-through system caused a significant depression in calcification for a period of up to 6 days. It is suggested that such initial calcification depressions after staining could affect absolute growth measurements and cause synergistic effects with experimental manipulation of environmental conditions unless an appropriate recovery period is allowed. Knowledge of coral skeletal growth is important in coelenterate physiology, ecology, geology, and geochemistry for assessment of organism viability, establishing environ- mental time scales with internal density bands, and for reconstruction of paleoenviron- mental or climatic variables using oxygen and carbon isotopes and certain trace metals (e.g., Buddemeier & Kinzie, 1976; Dodge & Vaisnys, 1980). A common technique for measuring growth uses sodium alizarin sulphonate [C6H,COC,H(OH,(S03Na)CO], alsoknown as alizarin red S, a stain which is incorporated as a permanent mark of color in the skeleton of reef corals (Barnes, 1970, 1972). Although staining has been widely employed (Buddemeier & Kinzie, 1976) to measure growth during or subsequent to the staining interval under natural or experimentally controlled conditions, there have been few studies to determine the effect of the staining procedure on coral behavior, physiology, skeletal chemistry, or growth. Lamberts (1978) has suggested that alizarin can be mildly toxic and it is important to understand the consequence of its use. We have investigated the effect of ahzarin red S stain on the calcification rate of hermatypic Diploria strigosa corals by using the buoyant weight technique (Jokiel et al., 1978). Our results demonstrate a depression in calcification rates for up to 6 days following staining. i Bermuda Biological Station for Research Contribution No. 963. 0022-0981/84/$03.00 0 1984 Elsevier Science Publishers B.V.