Mesophotic Coral Ecosystems

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?

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).

Figure 2.

The coral

Leptoseris

spp. dominates deeper MCEs in the

‘

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).