Spatial investigation on coral-turf algae interactions in fringing reefs of the Jordan Gulf of Aqaba- Red Sea

Abstract

Declines in coral cover are generally associated with increases in turf algae abundance- thus often termed a phase-shift from coral reef to an algae-dominated system. Turf algae coverage on the reef was measured at seven sites affected to varying degrees by industrial and recreational activities along the Jordanian coast of the Gulf of Aqaba (GoA). Using SCUBA to conduct transect surveys at two depths of each site, turf algae incidence was calculated in relation to total reef area (all live and dead reef) and in comparison to bare, algae-free dead coral reef. At every site, levels of turf algae were higher in the shallower depth (8 m), and more live reef was determined at the deeper depth (15 m). The two sites with the most turf algae, and least live reef coverage, are within close proximity to heavy industrial developments, while the site with the least turf algae and most live reef cover lies within a public beach, inside the Marine Park, which prohibits fishing. The average turf algae cover in relation to total reef area for all the sites and both depths is 28%, while bare dead coral to total reef proportion is a greater percentage: 40%. This may indicate that the potential phase-shift from coral reef to turf algae is not yet incurable, but with significant action, can be slowed, halted, or even reversed especially at sites in close proximity to anthropogenic influences such as construction and nutrient (i.e. Phosphorus and Nitrogen) over-enrichment.