Mesophotic Coral Ecosystems

Figure 2. The coral Leptoseris spp. dominates deeper MCEs in the ‘ Au ‘ au Channel between Maui and Lāna ‘ i in the Main Hawaiian Islands and provides habitat for fish, Psuedanthias thompsoni and Cheatodon milliaris (photo NOAA’s Hawai ‘ i Undersea Research Laboratory; see Figure 1 for location).

also appear only below 40 m (Spalding 2012). The benthic organisms that dominate the lower mesophotic appear to be largely distinct from the shallow-water community, and some species exhibit special physiological adaptations (Kahng et al. 2012b, 2014). Based on limited data, growth rates for shallow-water corals (e.g. Porites lobata ) decline with increasing depth, while growth rates of deep-water specialists (e.g. Leptoseris hawaiiensis ) in the lower mesophotic appear moderate (Grigg 2006, Kahng 2013). Growth rates of obligate heterotrophic suspension-feeding organisms (e.g. Antipathes griggi ) at mesophotic depths can be relatively rapid in areas of high current flow (Grigg 1976, Roark et al. 2006). There are limited published data on mesophotic fish communities in Hawai‘i. In general, fewer herbivores are found at mesophotic depths despite the presence of foliose macroalgae (Kosaki et al. 2012), and rates of fish endemism

are two times higher at mesophotic depths in comparison with shallow water (Kane et al. 2014). The majority (84 per cent) of fish species observed below 30 m are also found above 30 m. However, among all shallow and mesophotic species, only 46 per cent occur both shallower than 30 m and deeper than 60 m (Pyle pers. com.). Ecosystem connectivity between Hawai‘i’s mesophotic and shallow communities has not been studied in depth; however, a recent publication demonstrated that both vertical and horizontal connectivity exists for the endemic damselfish Chromis verater between shallow and mesophotic reefs across the archipelago (Tenggardjaja et al. 2014). Regular movement between shallow-water and mesophotic habitats has also been demonstrated for two common foraging predators, the Galapagos shark ( Carcharhinus galapagensis ) and the giant trevally ( Caranx ignobilis ), although a majority of their sustenance comes from shallow-water habitat (Hilting et al. 2013, Papastamatiou et al. 2015).

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS? 40

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