Recovery patterns of corals at Shabror Umm Gam’ar, Hurghada, Red Sea, Egypt, after the 1998 outbreak of Acanthaster planci

Abstract

Recovery patterns of corals were estimated after the Crown-of-thorns Starfish Acanthaster planci outbreak in 1998 at Shabror Umm Gam’ar, Hurghada, Egyptian Red Sea. The significance of using linear extrapolation was tested at ten sites by comparison with the actual average yearly recovery rates. A total of 15 permanent transects, each 10 m long, was monitored at 10 and 12 m depths at Shabror Umm Gam’ar for three years and the recovery rates were estimated by linear extrapolation. Ten other selected sites around Hurghada were monitored annually for nine years after the complete cessation of severe anchor damage. The recovery rates were estimated both by the actual annual recovery rate and by linear extrapolation. The recovery rate estimated by linear extrapolation did not differ significantly from the recovery rate of stony corals in the ten selected sites. However, an error of +7.69% to +17.5% increase in the extrapolated recovery rate exists and should be considered when handling the extrapolated recovery patterns of corals. Stony corals were characterised by having an extrapolated slow recovery time of 64.9 years in spite of the fast recovery rate (0.67% cover/year), and this is virtually due to the substantial devastation caused by A. planci. By contrast, soft corals were characterised by having a fast recovery time (RT) and recovery rate (RR) as they are not preferred prey of the Crown-of-thorns Starfish. The correlation coefficient is negative between recovery time (RT) and recovery rate (RR), strong between RT and cover required for complete recovery (CR), and weak between CR and RR. Diversity had an estimated fast recovery time (RT) of 4.3 years, indicating that the space cleared by A. planci was utilized by a high number of species (high diversity) having a smaller size (low percent cover).