A guide for planners and managers - IUCN

PART II
Protected Areas for Coral Reefs
Living corals exist as a veneer over a porous limestone base that accumulates
mainly through two mechanisms: the active growth of organisms (corals, molluscs,
and calcareous algae) and the cementation of calcareous debris (dead and broken corals
and molluscs) by encrusting organisms (algae, bryozoans, and sponges). The great
number of holes and crevices in a reef provide abundant shelters for fishes and
invertebrates, and are important fish nurseries (Figure II-2). In addition, highly
specialized creatures have become dependent for their survival on the reef environment.
It provides a solid substrate for many bottom-living organisms (clams, sponges,
tunicates, sea fans, anemones, and algae) to settle and grow.
Reefs show both high
and low endemism. Those
species that care for their young
may be highly endemic; for
example, “unique” subspecies
of a gastropod mollusc may
occur on two reefs separated by
less than 10 km. The majority
of species, however, distribute
their young through the plankton
via floating eggs. These
species may have a recruitment
line of many hundreds of kilometers
and thus a low level of
endemism.
FIGURE II-1.
Seagrass beds nurture many fishes and are an important component of coastal ecosystems (Florida Keys, U.S.A.).
FIGURE II-2.
Coral reefs provide an extraordinary variety of habitats and niches for
sealife species.
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Photo by Erkki Siirila.
Photo by Erkki Siirila.