operators,” such as holothurians and burrowing worms
and molluscs, aerate sediments and contribute to the productivity of sandy lagoons; “facilitators” such as herbivorous fishes and invertebrates keep algal biomass in check
that might otherwise limit coral settlement and survival.
Resilience in biota and functional roles is as much
dependent on the existence of the wave-resistant structure
as it is a contributor to it. A critical third pre-requisite is
a hydrodynamic setting that acts to retain the reef debris
within the existing reef footprint. Reefs with this combination of resilient populations of corals, other reef builders
and facilitators, high carbonate production, and strong
retention have been termed “production-dominated”
(Kleypas et al., 2001). These authors note that a reef ’s
potential for this strongly autonomous growth may be limited in three ways: by a location and hydrodynamic setting
that favors import and incorporation of exogenous sediments – marine or terrigenous (“import-dominated”
reefs); export of reef-generated sediments (“exportdominated”); or such a poor larval supply and/or conditions for coral growth that it cannot keep up with losses
caused by bioerosion (“bioerosion dominated”). This latter style is classically represented in back reef areas that
become isolated from the ocean by the coral reef’s own
profligate growth (Macintyre, 2007).
“Coral communities” (sensu Buddemeier and Hopley,
1988; i.e., those that do not advance beyond stage “a” in
Figure 1) are extreme examples of an “export-dominated”
setting. These corals settle directly on “non-reefal” substratum, and on their death, are physically and biologically
eroded down to silt, or fall off (precluding framework
accretion and sedimentary infilling), and are carried by
currents and gravity into places too deep, too turbulent
or too sandy for additional coral settlement or survival.
“Incipient reefs” (a term preferable to “coral reef communities”; Figure 2b) are coral reefs in the making. They
have had insufficient time to complete sufficient incremental vertical growth and “stepping out” to be considered a “coral reef.”
Summary
Two similar definitions (“coral reef” and coral-algal reef)
are provided, one strictly geological and one that specifies
living corals as a fundamental defining characteristic of
“coral reef.” The definition is then dissected, and allied
terms such as “coral community” and “coral reef community” discussed, noting the completely different meaning
of these terms in geology and ecology. The importance
of ecological processes in keeping up the supply of
building blocks (corals and reef debris) is discussed.
Differences in local environment and in particular, hydrodynamic setting, lead to different intergenerational performance of coral populations, and also the propensity for
reefs to act as sediment importers, producers or exporters,
or to be in a state of net loss due to bio-erosion. A place’s
environmental regime considered over decadal time scales
and up (including “normal” conditions and extreme
events) will determine the likelihood of a coral community
making the transition (Figure 1) to an “incipient coral
reef ” (early stages of development of a wave resistant
structure) and a “coral reef ” proper. Key determinants
are first, whether there is a sufficient density of corals in
a sufficiently large area that grow long enough and get
large enough to create a wave-resistant structure; and second, whether that structure gets large enough to attenuate
and refract waves and currents in a manner that promotes
the retention and compaction of its own biogenic sediments within and around itself.
Just as the terms “juvenile,” “mature,” and “senescent”
are applied to the coral reefs as geological structures, so
are they applied to the tracts of corals for which the structure is simply “substratum.” However, the links between
coral dynamics and reef development are poorly understood (Perry et al., 2008b). Improved understanding is
important, especially in light of serious, persistent, and
widespread declines in coral cover and resilience (e.g.,
Bellwood et al., 2004) and some very bleak projections
for the future of coral reefs under global climate change
(Veron, 2008).
Bibliography
Aronson, R. B., and Ellner, S. P., 2007. Biotic turnover on coral reefs:
a probabilistic approach. In Aronson, R. B. (ed.). Geological
Approaches to Coral Reef Ecology. New York: Springer, pp. 61–84.
Bellwood, D. R., Hughes, T. P., Folke, C., and Nyström, M., 2004.
Confronting the coral reef crisis. Nature, 429, 827–833.
Blanchon, P., Jones, B., 1997. Hurricane control on shelf-edge-reef
architecture around Grand Cayman. Sedimentology, 44, 479.
Buddemeier, R. W., and Hopley, D., 1988. Turn-ons and turn-offs:
causes and mechanisms of the initiation and termination of coral
reef growth. Proceedings of the Sixth International Coral Reef
Symposium, 1, 253–261.
Darwin, C. R., 1842. The Structure and Distribution of Coral Reefs.
London: Smith, Elder, 214 pp.
Done, T. J., 1982. Patterns in the distribution of coral communities
across the central Great Barrier Reef. Coral Reefs, 1, 95–107.
Done, T. J., 1992. Phase shifts in coral reefs and their ecological significance. Hydrobiologia, 247, 121–132.
Done, T. J., Ogden, J. C., Wiebe, W. J., and Rosen, B. R., 1996. Biodiversity and ecosystem function of coral reefs. In Mooney, H. A.,
Cushman, J. H., Medina, E., Sala, O. E., Schultze, E. D. (eds.),
Functional Roles of Biodiversity: A Global Perspective. Chichester:
Wiley, pp. 393–429.
Fowler, H. W., 1929. The Concise Oxford Dictionary of Current
English, 2nd edn. Oxford, UK: Clarendon Press.
Hallock, P., 2001. Coral reefs, carbonate sediments, nutrients and
global change. In Stanley, G. D. Jr. (ed.). The History and Sedimentology of Ancient Reef Systems. New York: Kluwer/Plenum
pp. 387–427.
Harrington, L., Fabricius, K., De’ath, G., and Negri, A., 2004. Recognition and selection of settlement substrata determine postsettlement survival in corals. Ecology, 85, 3428–3437.
Hopley, D., Smithers, S. G., and Parnell, K. E., 2007. The Geomorphology of the Great Barrier Reef: Development, Diversity and
Change. Cambridge: Cambridge University Press, 532 pp.
James, N. P., and Macintyre, I. G., 1985. Carbonate depositional
environments: modern and ancient. Part 1; Reefs: zonation,
depositional facies, diagenesis. Colorado School of Mines Quarterly, 80(3), 70.
266
CORAL REEF, DEFINITION
and molluscs, aerate sediments and contribute to the productivity of sandy lagoons; “facilitators” such as herbivorous fishes and invertebrates keep algal biomass in check
that might otherwise limit coral settlement and survival.
Resilience in biota and functional roles is as much
dependent on the existence of the wave-resistant structure
as it is a contributor to it. A critical third pre-requisite is
a hydrodynamic setting that acts to retain the reef debris
within the existing reef footprint. Reefs with this combination of resilient populations of corals, other reef builders
and facilitators, high carbonate production, and strong
retention have been termed “production-dominated”
(Kleypas et al., 2001). These authors note that a reef ’s
potential for this strongly autonomous growth may be limited in three ways: by a location and hydrodynamic setting
that favors import and incorporation of exogenous sediments – marine or terrigenous (“import-dominated”
reefs); export of reef-generated sediments (“exportdominated”); or such a poor larval supply and/or conditions for coral growth that it cannot keep up with losses
caused by bioerosion (“bioerosion dominated”). This latter style is classically represented in back reef areas that
become isolated from the ocean by the coral reef’s own
profligate growth (Macintyre, 2007).
“Coral communities” (sensu Buddemeier and Hopley,
1988; i.e., those that do not advance beyond stage “a” in
Figure 1) are extreme examples of an “export-dominated”
setting. These corals settle directly on “non-reefal” substratum, and on their death, are physically and biologically
eroded down to silt, or fall off (precluding framework
accretion and sedimentary infilling), and are carried by
currents and gravity into places too deep, too turbulent
or too sandy for additional coral settlement or survival.
“Incipient reefs” (a term preferable to “coral reef communities”; Figure 2b) are coral reefs in the making. They
have had insufficient time to complete sufficient incremental vertical growth and “stepping out” to be considered a “coral reef.”
Summary
Two similar definitions (“coral reef” and coral-algal reef)
are provided, one strictly geological and one that specifies
living corals as a fundamental defining characteristic of
“coral reef.” The definition is then dissected, and allied
terms such as “coral community” and “coral reef community” discussed, noting the completely different meaning
of these terms in geology and ecology. The importance
of ecological processes in keeping up the supply of
building blocks (corals and reef debris) is discussed.
Differences in local environment and in particular, hydrodynamic setting, lead to different intergenerational performance of coral populations, and also the propensity for
reefs to act as sediment importers, producers or exporters,
or to be in a state of net loss due to bio-erosion. A place’s
environmental regime considered over decadal time scales
and up (including “normal” conditions and extreme
events) will determine the likelihood of a coral community
making the transition (Figure 1) to an “incipient coral
reef ” (early stages of development of a wave resistant
structure) and a “coral reef ” proper. Key determinants
are first, whether there is a sufficient density of corals in
a sufficiently large area that grow long enough and get
large enough to create a wave-resistant structure; and second, whether that structure gets large enough to attenuate
and refract waves and currents in a manner that promotes
the retention and compaction of its own biogenic sediments within and around itself.
Just as the terms “juvenile,” “mature,” and “senescent”
are applied to the coral reefs as geological structures, so
are they applied to the tracts of corals for which the structure is simply “substratum.” However, the links between
coral dynamics and reef development are poorly understood (Perry et al., 2008b). Improved understanding is
important, especially in light of serious, persistent, and
widespread declines in coral cover and resilience (e.g.,
Bellwood et al., 2004) and some very bleak projections
for the future of coral reefs under global climate change
(Veron, 2008).
Bibliography
Aronson, R. B., and Ellner, S. P., 2007. Biotic turnover on coral reefs:
a probabilistic approach. In Aronson, R. B. (ed.). Geological
Approaches to Coral Reef Ecology. New York: Springer, pp. 61–84.
Bellwood, D. R., Hughes, T. P., Folke, C., and Nyström, M., 2004.
Confronting the coral reef crisis. Nature, 429, 827–833.
Blanchon, P., Jones, B., 1997. Hurricane control on shelf-edge-reef
architecture around Grand Cayman. Sedimentology, 44, 479.
Buddemeier, R. W., and Hopley, D., 1988. Turn-ons and turn-offs:
causes and mechanisms of the initiation and termination of coral
reef growth. Proceedings of the Sixth International Coral Reef
Symposium, 1, 253–261.
Darwin, C. R., 1842. The Structure and Distribution of Coral Reefs.
London: Smith, Elder, 214 pp.
Done, T. J., 1982. Patterns in the distribution of coral communities
across the central Great Barrier Reef. Coral Reefs, 1, 95–107.
Done, T. J., 1992. Phase shifts in coral reefs and their ecological significance. Hydrobiologia, 247, 121–132.
Done, T. J., Ogden, J. C., Wiebe, W. J., and Rosen, B. R., 1996. Biodiversity and ecosystem function of coral reefs. In Mooney, H. A.,
Cushman, J. H., Medina, E., Sala, O. E., Schultze, E. D. (eds.),
Functional Roles of Biodiversity: A Global Perspective. Chichester:
Wiley, pp. 393–429.
Fowler, H. W., 1929. The Concise Oxford Dictionary of Current
English, 2nd edn. Oxford, UK: Clarendon Press.
Hallock, P., 2001. Coral reefs, carbonate sediments, nutrients and
global change. In Stanley, G. D. Jr. (ed.). The History and Sedimentology of Ancient Reef Systems. New York: Kluwer/Plenum
pp. 387–427.
Harrington, L., Fabricius, K., De’ath, G., and Negri, A., 2004. Recognition and selection of settlement substrata determine postsettlement survival in corals. Ecology, 85, 3428–3437.
Hopley, D., Smithers, S. G., and Parnell, K. E., 2007. The Geomorphology of the Great Barrier Reef: Development, Diversity and
Change. Cambridge: Cambridge University Press, 532 pp.
James, N. P., and Macintyre, I. G., 1985. Carbonate depositional
environments: modern and ancient. Part 1; Reefs: zonation,
depositional facies, diagenesis. Colorado School of Mines Quarterly, 80(3), 70.
266
CORAL REEF, DEFINITION