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 tidal range and turbidity. AVHRR channel-1 reflectance, which was strongly correlated with suspended sediment concentration (SSC), demonstrated that SSC is due to tidal resuspension of sediments, and increases with increasing tidal range. Underwater surveys and reef coring revealed that reef development diminishes with increasing SSC toward Broad Sound. 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 stages of reef growth. Others appear to be coral communities growing as thin veneers on exposed rock surfaces, rather than coral reef communities with capacity for reef-building. Still others developed reef flats earlier in the Holocene, and have since turned-off.