Breakwater reef terminology and geomorphic zonation of shallow benthic seascapes in the Greater Caribbean.

The upper profile shows that BW reefs are three-dimensional bio-accretionary benthic structures (geoforms) composed of two geomorphic units—the back-reef and the reef-front—either side of the crestline, where fair-weather waves break. These two units constitute the BW reef deposit. As well as covering the reef deposit, corals are also found veneering non-reefal benthic zones in the wider ecological seascape, such as in the adjacent lagoon and inner fore-reef shelf. The outer fore-reef shelf can also be a depocentre for sand and submerged reef development. The lower image illustrates how a 1-km long section of each reef is sampled to determine 10 morphometric parameters: polygons delineate back-reef and reef front areas, which combine to give total deposit area and size ratio; actual total crestline length is compared to end-to-end length to derive sinuosity, and its persistence is derived from summing the gaps as a percentage of the total length; the reef-front slope is derived from the average distance from the crestline to the mid-shelf break (or 15 m isobath); These 10 morphometric parameters are used to statistically analyse the geomorphology of reef types. Drone image courtesy of Dr. L. Alvarez-Filip.