Mesophotic Coral Ecosystems

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?

typically found at depths from 30–40 m and extending to

depths of over 150 m in tropical and subtropical waters

(Hinderstein et al. 2010; Figure 2.1). The occurrence of MCEs

is dependent not only on light availability, but also on water

temperature and quality, substrate and geomorphology.

• MCEs are defined by the presence of corals that have

zooxanthellae and to some extent are light-dependent.

Some corals that live in the mesophotic depth range, such

as black corals and octocorals, are azooxanthellate and not

dependent on light.

• MCEs are populated with organisms typically associated

with shallow coral reefs: macroalgae, scleractinian corals,

octocorals, antipatharians, sponges, a wide assortment

of other sessile invertebrates and families of fish common

on shallow reefs (Figure 2.2), as well as species unique to

mesophotic depths or deeper.

• Dominant communities providing structural habitat include

macroalgae, sponges and corals.

• MCEs are defined by their ecology, not their absolute depth range.

• Few of the world’s known MCEs have been mapped or studied.

The more we look, the more we find (Figure 2.3).

Key facts about MCEs

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Primary MCE study areas

Preliminary MCE surveys

Almost nothing known

Current extent of MCE studies

Source: Adapted from Richard Pyle, unpublished data

Figure 2.3.

Extent of MCE investigations to date (adapted from Richard Pyle unpublished data). At least 80 countries (those with

documented shallow reefs; Spalding et al. 2001) have potential MCEs. Countries that do not have surface reefs, but potentially have

MCEs, include those on the west coasts of Africa and South America.

Figure2.2.

ManyMCEs aredominatedbymacroalgae, gorgonian

and antipatharian corals, sponges and other invertebrates as

illustrated in this image from 130 m in Pohnpei, Federated States

of Micronesia (photo Sonia J. Rowley).

However, there is little understanding of the degree

to which these factors (and potentially others, such as

nutrient levels, currents and competition) control the

distribution and community structure of MCEs (Puglise

et al. 2009).