Environmental controls on growth of the massive coral Porites

Annual density banding provided growth characteristics for 245 similar-size d, massive colonies of Porites from similar locations on 29 reefs from acro ss the length and breadth of the Great Barrier Reef (GBR), Australia. Value s obtained were density, extension rate, and calcification rate. Tissue thi ckness, the depth to which skeletons were occupied by tissue at the time of collection, was also measured. Extension rate, calcification rate, and tis sue thickness were significantly greater at the top of colonies than at the sides. Extension rate and calcification rate decreased from north to south along the GBR (latitudinal range of similar to 9 degrees) and were signifi cantly and directly related to annual average sea surface temperature (SST; range similar to 25-27 degrees C). For each 1 degrees C rise in SST, avera ge annual calcification increased by 0.39 g cm(-2) year(-1) and average ann ual extension increased by 3.1 mm year(-1) (c.f. average values of 1.63 g c m(-2) year(-1) and 12.9 mm year(-1), respectively). Density was inversely c orrelated with extension rate and increased with distance offshore. Data fo r massive Porites colonies from the GBR were extended though 20 degrees of latitude and an average annual SST range of 23-29 degrees C using published data for the Hawaiian Archipelago (Grigg, R.W., 1981. Coral reef developme nt at high latitudes in Hawaii. Proc. 4th Int. Coral Reef Symp., Manila, Vo l. 1, pp. 687-693; Grigg, R.W., 1997. Paleoceanography of coral reefs in th e Hawaiian-Emperor Chain - revisited. Coral Reefs 16, S33-S38) and Phuket, Thailand (Scoffin. T.P., Tudhope. A.W., Brown. B.E., Chansang. H., Cheeney. R.F., 1992. Patterns and possible environmental controls of skeletogenesis of Porites lutea, South Thailand. Coral Reefs 11, 1-11). The response of c alcification rate to temperature remained linear. Variation in annual avera ge SST accounted for 84% of the variance. For each 1 degrees C rise in SST, average annual calcification increased by 0.33 g cm(-2) year(-1) and avera ge annual extension increased by 3.1 mm year(-1) (c.f. average values of 1. 50 g cm(-2) year(-1) and 11.6 mm year(-1), respectively). The sensitivity o f calcification rate in Porites to SST, combined with observed 20th Century increases in SSTs, suggests that calcification rates may have already sign ificantly increased along the GBR in response to global climate change. (C) 2000 Elsevier Science B.V. All rights reserved.