Scale-Invarient Fractal Patterns of Coral Communities: Evidence from Remote Sensing (Arabian Gulf, Dubai, U.A.E.)

The occurrence of power-law relationships between frequency and size of facies patches has been identified in both modern and ancient carbonate depositional bodies. However, quantification of the lateral extent of facies distribution in such systems, which vary on scales of centimeters to tens of kilometers, is notoriously difficult and remote sensing methods are increasingly becoming the tool of choice. In this study, facies patterns and their spatial relationships were quantitatively investigated in an Arabian Gulf shallow subtidal carbonate ramp setting in Dubai using a synergy of IKONOS satellite imagery and vessel-based acoustic bathymetry survey. The spatially detailed bathymetry was used as input into an empirical correction for the effect of the water column on the satellite imagery, facilitating classification of eight dominant facies types, using a classifier trained exclusively by hyperspectral in situ optical measurements of substrate reflectance. Secondly, the bathymetry was interpolated to represent a model of seafloor topography, which, when combined with the classified IKONOS imagery, yielded a three-dimensional model of facies distribution on the seabed. Both ground-verification and the predictive map derived for the IKONOS imagery confirm the fragmented nature of carbonate benthos in the study area, with patch sizes found to vary between 16m2 (the spatial resolution of the imagery) and 900 m2. The patch distribution of three assemblages of live and dead corals on extensive (but also fragmented hardground pavements was investigated using a variety of spatial statistics and it was found that the relationship between patch size and frequency approximate to a power-law relationship (linear in the log-log domain) over several orders of magnitude. The area is known to be subjected to recurrent and cyclic thermal induced mass mortality events on a decadal time scale, inhibiting reef framework development and likely to be a controlling mechanism in the patchiness of the coral communities.