CORAL-REEF DEVELOPMENT UNDER NATURALLY TURBID CONDITIONS - FRINGING REEFS NEAR BROAD-SOUND, AUSTRALIA

Reef coring and NOAA/AVHRR imagery were used to examine differences in reef colonisation and accumulation across a gradient of increasing ti dal range and turbidity. AVHRR channel-1 reflectance, which was strong ly correlated with suspended sediment concentration (SSC), demonstrate d that SSC is due to tidal resuspension of sediments, and increases wi th increasing tidal range. Underwater surveys and reef coring revealed that reef development diminishes with increasing SSC toward Broad Sou nd. Few reefs near Broad Sound have formed reef flats; those that have are thinner and accumulated more slowly during the Holocene. The many submerged reefs in this area represent a mixture of reef ''turn-ons'' and ''turn-offs''. Some are probably incipient reefs in the early sta ges of reef growth. Others appear to be coral communities growing as t hin veneers on exposed rock surfaces, rather than coral reef communiti es with capacity for reef-building. Still others developed reef flats earlier in the Holocene, and have since turned-off.