Spatial differentiation of coral species related to wave energy along the Changqi coast, Hainan island, southern China

The regularities of the composition and the spatial distribution of hermatypic coral community is an essential aspect of coral reef ecosystem studies. The relationship between the structure and spatial distribution of hermatypic coral communities and hydrodynamics and wave energy, along the Changqi coast, are investigated. Differences in abundance of hermatypic coral species, at different depths, were found; these were related mainly to the varying influence of waves. Under average weather conditions, the wave energy was dissipated regularly at a depth of 2 m. Here, the coral cover was the lowest of all of the depths. However, corals growing in that area is adapted to the conditions; therefore, wave damage was low. The areas at 5–6 m water depth were influenced by waves primarily during episodes of extreme weather, with high wave energy resulting in severe damage of the corals. The coral cover in this depth was the highest observed, but the corals were generally smaller and had a short growth period. These findings indicate that the strong waves damaged particularly the weak corals, such as Acropora sp. and Montipora sp., during these short term events. Nevertheless, upon the return of normal conditions, coral communities can grow back and reproduce asexually in the damaged areas. As a result of this regrowth, Acropora sp. and Montipora sp. were highly abundant in areas at a depth of 5 m. It appears that knowledge on the physical setting, i.e. the relationship between wave properties and the spatial distribution patterns of corals, is essential for understanding coral reef succession rules; likewise, protection and recovery mechanisms of the coral reef ecosystem.

► The study of the regularities of the structure and spatial distribution of hermatypic coral communities is an essential aspect of the study of coral reef ecosystems. ► The purpose of this study is to investigate the relationship between the properties of waves and the structure of hermatypic coral communities in Changqi. ► This thesis analyses the features of water flow and wave energy as well as the regularities in the spatial distribution of hermatypic corals at that location. ► In addition, it discusses the influence of waves on the spatial distribution patterns of the hermatypic corals. ► The study found that the distribution of corals first increased and then decreased with water depth. ► The distributions of different coral species showed peaks at different depths. ► These peaks were the result of depth-related variations in the characteristics of the waves. ► The study of the relationship between wave properties and the spatial distribution patterns of corals is highly relevant to the study of succession rules governing coral reefs and to the protection and recovery of the coral reef ecosystem.