Patterns of coral settlement in an extreme environment: the southern Persian Gulf (Dubai, United Arab Emirates)

Coral settlement is a key ecological process in the maintenance, recovery and resilience of coral reef ecosystems. Coral reefs in the Persian Gulf survive in one of the world's most extreme environments, yet there remains limited knowledge of the role of coral settlement considered critical for maintaining population dynamics. Spatial and temporal patterns of coral settlement were examined at 6 sites in Dubai, United Arab Emirates, using settlement tiles deployed and collected every 3 mo from 2009 to 2011 following coral community surveys. Settlement was highly seasonal with the highest settlement rates between June and August (3.2 spat tile(-1) +/- 0.21 SE), when summer sea temperatures approached 35 degrees C. There was a smaller settlement pulse between September and November, but no settlement between December and May. Settlement was observed 1 to 4 mo after the major spawning season (April and May), suggesting either delayed settlement of larvae, or spatial and/or taxonomic disparity between studies of reproduction versus settlement. Settlement rates varied significantly among sites, but spatial variation was consistent between the 2 years of the study, suggesting strong effects of local environmental conditions or local coral assemblages. Poritidae and Acroporidae comprised 27 and 11% of the spat respectively, there were no Pocilloporidae and the most abundant coral spat (61%) were from other, not identifiable, families. These data indicate that observed long-term shifts in the community structure of adult coral assemblages are being reinforced through a combination of settlement and post-settlement processes, such that there is limited scope for recovery of former Acropora dominated coral assemblages in the Persian Gulf.