Download Information Fact Sheet on Coral Reef

Ministry of Environment, Lands and Agriculture Development
ENVIRONMENT AND CONSERVATION DIVISION
Information Fact Sheet on Coral Reef
Background
Coral reefs are nature’s richest realm that derive
their primary energy from solar radiation (sun
energy) and thrive in areas of maximum sunlight.
Coral reef development is optimum (highest) in
the following conditions:
 Where sea temperatures are warmest
between the latitudes of 30 degrees
north and south.
 In clean, clear water and relatively
shallow depths.
 Energy supply originating from plants,
which only thrive in shallow, sun
drenched areas.
Productivity is decreased in areas subjected to
dirty, sediment-laden water (this is the case around
the mouth of large rivers- but this is not applicable
to Kiribati since there are no rivers existing). Coral
growth is usually sparse immediately adjacent to
the shore but often increases dramatically as one
swim seaward.
What are coral reefs?
Coral reef represent a development episode of
only 5,000 years ago. This development is closely
tied to fluctuating sea levels. Most individual coral
animals exist in colonies. These are the primary
building blocks of the reef, which depend on
microscopic unicellular plants (zooxanthellae) that
live within their tissue to provide the bulk of their
nutrition. Zooxanthellae facilitate the growth and
secretion of the important calcium carbonate
skeleton that provides the reef’s structural
framework. Beautiful living corals that adorn the
reef are very small part of the overall reef structure
that form a thin veneer that overlies a solid
limestone (calcium carbonate) foundation. This
platform is composed of skeletal remains of past
coral generations as well as numerous reef dwelling
animals that have hard parts or shells composed of
calcium carbonate. Contributors are various
molluscs, crustaceans and echinoderms including
forams (single celled organisms), sponges, soft
corals, worms and fishes. Certain plants such as
green algae of the genus Halimeda secrete calcium
carbonate and in some areas it contributes to
bottom sediments.
A great variety of animals and plants provide raw
ingredients or basic building blocks for the reef’s
foundation, which are bound together into a
consolidated structure by an important group of
plants known as calcareous or coralline red algae.
Unlike real plants, red algae form a pink or red
colored crust of limestone that cements the reef’s
framework.
In most cases, given the right conditions of clean,
warm water, coral will proliferate in shallow seas.
Why do coral reefs support such a
superabundance of life?
Tiny zoozanthellae are the real secret of coral reefs
success. These utilize sunlight and carbon dioxide
to produce energy rich organic compounds. The
plants are the food source of a host of
invertebrates and fishes, thus forming the vital first
step in the coral reef food chain, referred to as a
feeding web due to the tangled inter-relationships
of consumer and consumed organisms.
Coral reefs are extremely complex systems,
consisting of numerous microhabitats. The huge
number of species found on coral reefs is a direct
reflection of the high number of habitat
opportunities afforded by this environment,
including thousands of unseen organisms living
around the area. Diverse communities live under
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rocks and dead coral slabs or in the crevices and
fissures of the reef. An incredible number of
species are associated with live and dead coral
heads, whereby a single head may contain more
than 100 species of worms and numerous
assortments of other organisms.
Symbiotic relationship is also a common feature of
coral reefs systems. For instance, sponges, soft and
hard corals, echinoderms and ascidians frequently
have crustaceans, molluscs, worms and fishes
living on their outer surface or within internal
cavities. A community of macroscopic and
microscopic animals lives below the surface of
sand and rubble bottoms. Finally there is a legion
of microscopic creatures that live either on the
reef’s surface or in mid-water directly above. The
latter are referred to as zooplankton, a mixture of
larval and adult forms that are important food
sources for many reef inhabitants.
Every species found on coral reefs has distinct life
style that allows to fulfill, their basic needs:
 Must obtain nutrients from the
surrounding environment to sustain
energy levels.
 Must exchange oxygen and carbon
dioxide (respiration).
 Must avoid predation and
 Must reproduce to ensure the survival of
future generations.
Environmental conditions exert a great influence
in determining how an individual organism copes
with its basic needs. Over thousands of years,
succeeding generations of a particular species
become modified in a manner that allows them to
efficiently utilize their environment. For instance,
species of corals in exposed shallows tend to be
much more robust, hence resistant to wave
damage. Those living on deeper parts of the reef
frequently exhibit a more delicate structure and
may grow to a very large size.
Reef-building corals in the genus Pocillopora are
more or less restricted to waters warmer than
18ºC. In coral reef ecosystems, many large species
exhibit spawning migrations to specific breeding
sites. Among groupers (family: Serranidae), in
particular, spawning sites are strongly localized (a
few thousand m2 of reef edge) and are predictably
occupied for short periods at the same time each
year (5- 15 days). The spawning aggregations are
dense with fish that have migrated from tens of
kilometers away and are attractive to fishers
because these high value species are more
susceptible to catch.
Why are coral reefs important?
Coral reefs have many important uses to many
people living in Kiribati. Their diverse economic,
medical, geological, biological and
cultural/traditional values have made them unique
and priceless resources, where they exist. For
instance, activities on reefs generate employment
to many people with both extractive (e.g. fishing
and shelling) and non-extractive activities (e.g. ecotourism and recreation). More than 90% of the
animal protein consumed by I-Kiribati comes
from marine fish that live around coral reefs. Coral
reefs have been a source of good fishing spots to
many people in Kiribati. Many people would go to
other coral reef areas, once they feel that the fish
abundance of their usual fishing spot is depleting.
Reef tourism (e.g. scuba diving industry in Buariki,
North Tarawa that has been conducted to private
house guests residing at Mauri Paradise Motel) has
been recently introduced on a commercial but
small basis in the capital island- South Tarawa,
where most economic development is
concentrated.
Coral reefs (e.g. blue corals) have important
pharmaceutical and medicinal values. Whether
fringing or barrier coral reefs, they also serve to
break up the force of incoming waves before they
hit the shore, hence essential in minimizing coastal
erosion. Large evidence of coastal erosion has
become prominent in areas around South Tarawa,
where coral mining for either infrastructure
development or construction are common.
Culturally, coral reefs are also important as a
source of food, handicrafts, etc to many people in
Kiribati.
What are the threats facing the health of coral
reefs?
The health of coral reefs, are continually
threatened by many sources that include natural
events, commercial and recreational activities. In
Kiribati the impacts of recreational activities on
coral reefs are not significant as coral reef tourism
is not very common. Natural events such as heavy
storms, crown of thorn starfish outbreak and coral
reefs bleaching can cause severe damage to reefs
and result in death to the diverse marine fauna
living within. For more details on the threats, see
the attached.
Why do we need to conserve and protect coral
reefs from degradation?
Coral reefs, like mangroves are also priceless
resources that need some form of protection
against degradation. They have been a source of
subsistence and commercial living to people in
Kiribati for many generations (main source of
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animal protein, etc). With the increase in human
population as is experienced in South Tarawa, the
capital island, coral reefs are susceptible to overexploitation, over-harvesting and eventual death of
corals. Should this happens, then equal sharing of
benefits arising from coral reefs, between the
current and future generations in Kiribati will not
be greatly disadvantaged.
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