The Influence of Wave Exposure on Coral Community Development on Man-Made Breakwater Reefs, with a Comparison to a Natural Reef

Breakwaters dominate shorelines in many coastal urban areas, providing substantial hard-bottom habitat upon which diverse and abundant reef communities develop. In recognition of their potential ecological and economic importance, there is increasing interest in understanding how design features can influence community development. We investigated the influence of wave exposure on breakwater coral communities in Dubai, United Arab Emirates. Coral community composition, cover, size structure, recruitment, mortality, and growth rates were compared quarterly between two windward and two leeward breakwater sites for 1 yr to explore the influence of wave exposure on coral community development. Comparisons also were made with a natural coral reef to gain an understanding of how community structure and dynamics compare between these habitats. Benthic and water column sediment particle sizes were also analyzed. Leeward breakwaters contained a low-cover coral community dominated by small colonies with high mortality compared with windward breakwaters and the natural reef. Windward breakwater coral communities had comparable recruitment, mortality, and growth rates as the natural reef. Fine sediments (< 63 μm) dominated the benthos and water column on leeward breakwaters, while windward breakwaters and the natural reef were dominated by sediments with larger size classes (> 125 μm), likely as a result of differences in wave action among reef types. Overall, these results suggest that leeward breakwaters represent sub-optimal habitats for coral community development. However, with appropriate design, breakwaters can develop diverse and abundant coral communities with comparable coral cover, demographics, and growth rates to those on the natural reef in Dubai.