Coral reefs are
aragonite
structures produced by living organisms, found in marine waters
containing few nutrients. In most reefs, the predominant organisms
are stony
corals, colonial
cnidarians that secrete an
exoskeleton of
calcium carbonate. The accumulation of
skeletal material, broken and piled up by wave action and
bioeroders, produces a calcareous formation that
supports the living corals and a great variety of other animal and
plant life.
Coral reefs most commonly live in tropical waters, but deep water
and cold water corals exist on a much smaller scale.
Globally, coral reefs are under threat from
climate change,
ocean acidification,
blast fishing, overuse of reef resources, and
harmful land-use practices. High nutrient levels such as those
found in runoff from agricultural areas can harm reefs by
encouraging excess
algae growth.
Formations
Diagram of a fringing coral
reef.
Coral reefs can take a variety of forms, defined in following:
- Fringing reef – a
reef that is directly attached to a shore or borders it with an
intervening shallow channel or lagoon.
- Barrier
reef – a reef separated from a mainland or island
shore by a deep lagoon (see Great Barrier
Reef).
- Patch reef – an isolated, often circular reef,
usually within a lagoon or embayment.
- Apron reef – a short reef resembling a
fringing reef, but more sloped; extending out and downward from a
point or peninsular shore.
- Bank reef – a linear or semi-circular
shaped-outline, larger than a patch reef.
- Ribbon reef – a
long, narrow, somewhat winding reef, usually associated with an
atoll lagoon.
- Atoll reef – a more or
less circular or continuous barrier reef extending all the way
around a lagoon without a central island.
- Table reef – an isolated reef, approaching an
atoll type, but without a lagoon.
Distribution
Locations of coral reefs.
Ocean currents affect the settling of
coral reefs
Coral
reefs are estimated to cover , with the Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and
the Pacific) accounting
for 91.9% of the total. Southeast Asia accounts for 32.3% of
that figure, while the Pacific including
Australia accounts for 40.8%.
Atlantic and Caribbean coral reefs only account for 7.6%.
Coral reefs are rare along the
American
west coast, as well as along the
African west
coast. This is due primarily to
upwelling
and strong cold coastal currents that reduce water temperatures in
these areas (respectively the Peru, Benguela and Canary streams).
Corals are seldom found along the coastline of
South Asia from the eastern tip of India (Madras)
to the border of Bangladesh and Myanmar.
They are also rare
along the coast around north-eastern South
America and Bangladesh due to the freshwater release from the Amazon and Ganges Rivers
respectively.
In addition, very little coral reef exist between Senegal and
Gabon, as well as between the western coast of Columbia and the
western coast of Peru. This, although respectively, the
Canary/Benguela, nor the Peru current has an impact here.
Although corals exist both in temperate and tropical waters,
shallow-water reefs form only in a zone extending from 30°N to 30°S
of the equator. Tropical corals do not grow at depths of over .
Temperature has less of an effect on the distribution of tropical
coral (the only exeption being the region between the western coast
of Peru to the eastern coast of Chili), but it is generally
accepted that they do not exist in waters below 18
°Celsius, and that the optimum temperature is
26-27 °Celsius for most coral reefs. The reefs in the Persian
Gulf however have adapted to temperatures of 13 °Celsius in
winter and 38 °Celsius in summer.
Deep water coral is more still exceptional
since it can exist at greater depths and colder temperatures.
Although deep water corals can form reefs, very little is known
about them.
Famous coral reefs and reef areas of the world
include:
- The
Great Barrier
Reef - largest coral reef system in the world, Queensland, Australia.
- The
Belize Barrier
Reef - second largest in the world, stretching from
southern Quintana Roo, Mexico along the coast of Belize to the Bay
Islands of Honduras.
- The
New Caledonia
Barrier Reef - second longest double barrier reef in the world,
with a length of about .
- The
Andros,
Bahamas Barrier Reef - third largest in the world,
following the east coast of Andros Island, Bahamas, between Andros
and Nassau.
- The
Red Sea Coral Reef - located off the coast of Israel,
Egypt, Sudan, Eritrea, Djibouti, Somalia, Jordan, Saudi Arabia, and
Yemen.
- Pulley Ridge -
deepest photosynthetic coral reef, Florida.
- Numerous reefs scattered over the Maldives.
- Ghe
Raja Ampat
Islands in Indonesia's West
Papua province offer the highest known marine
diversity.
Biology
Anatomy of a coral polyp.
Coral consists of accumulations of individual organisms called
polyps, arranged in diverse shapes. Reefs grow
as polyps along with other organisms deposit
calcium carbonate, the basis of coral, as
a skeletal structure beneath and around themselves, pushing the
coral's "head" or
polyps upwards and outwards.
Waves, grazing fish (such as
parrotfish),
sea urchins,
sponges, and other forces and organisms break
down coral skeletons into fragments that settle into spaces in the
reef structure. Many other organisms living in the reef community
contribute skeletal
calcium
carbonate in the same manner.
Coralline algae are important contributors
to reef structure in those parts of the reef subjected to the
greatest forces by waves (such as the reef front facing the open
ocean). These algae deposit limestone in sheets over the reef
surface, thereby strengthening it.
Reef-building or hermatypic corals are only found in the
photic zone (above 50 m depth), the depth
to which sufficient sunlight penetrates the water for
photosynthesis to occur. Coral polyps do not
photosynthesize, but have a
symbiotic
relationship with single-celled organisms called
zooxanthellae; these cells within the tissues
of the coral polyps carry out photosynthesis and produce excess
organic nutrients that are then used by the coral polyps. Because
of this relationship, coral reefs grow much faster in clear water,
which admits more sunlight. Indeed, the relationship is responsible
for coral reefs in the sense that without their symbionts, coral
growth would be too slow for the corals to form impressive reef
structures. Corals get up to 90% of their nutrients from their
zooxanthellae symbionts.
Corals can reproduce both sexually and asexually. An individual
polyp may use both reproductive modes within its lifetime. Corals
reproduce sexually by either internal or external fertilization.
The reproductive cells are found on the mesentery membranes that
radiate inward from the layer of tissue that lines the stomach
cavity. Some mature adult corals are hermaphroditic; others are
exclusively male or female. A few even change sex as they
grow.
Internally fertilized eggs develop in the polyp for a period
ranging from days to weeks. Subsequent development produces a tiny
larva, known as a planula. Externally fertilized eggs develop
during synchronized spawning. Polyps release eggs and sperm into
the water simultaneously. Eggs disperse over a large area. Spawning
depends on four factors: time of year, water temperature, and tidal
and lunar cycles. Spawning is most successful when there is little
variation between high and low tides. The less water movement, the
better the chance for fertilization. Ideal timing occurs in the
spring. Release of eggs or planula larvae usually occurs at night
and is sometimes in phase with the lunar cycle (3–6 days after a
full moon). The period from release to settlement lasts only a few
days, but some planulae can survive afloat for several weeks (7,
14). They are vulnerable to heavy predation and adverse
environmental conditions. For the lucky few who survive to attach
to substrate, the challenge comes from competition for food and
space.
Ecology and biodiversity
Coral reefs support extraordinary
biodiversity although they are located in
nutrient-poor waters. The process of
nutrient cycling between corals,
zooxanthellae, and other reef
organisms explains why reefs flourish in these waters: recycling
ensures that fewer nutrients are needed overall to support the
community.
Cyanobacteria provide soluble
nitrates for the reef via
nitrogen fixation. Corals absorb
nutrients, including inorganic nitrogen and
phosphorus, directly from the water, and they
feed upon
zooplankton that pass the
polyps via water motion. Thus,
primary productivity on a coral reef is
very high, which results in high
biomass per square meter, at 5-10g C
m
−2 day
−1. Producers in coral reef
communities include the
symbiotic
zooxanthellae, sponges,
marine worms,
seaweed,
coralline algae (especially
small types called turf algae), ... although scientists disagree
about the importance of these particular organisms.
Coral reefs often depend on other habitats, such as
seagrass meadows and
mangrove forests in the surrounding area for
the supply of nutrients. Seagrass and mangroves supply dead plants
and animals which are rich in nitrogen and also serve to feed fish
and animals from the reef by supplying wood and vegetation. Reefs
in turn protect mangroves and seagrass from waves and produce
sediment for the mangroves and seagrass to
root in.
Coral reefs are home to a variety of tropical or reef
fish which can be distinguished. These include:
- fish that adjust the coral (such as Labridae and parrotfish) These types of fish feed either on
small animals living near the coral, seaweed, or on the coral
itself. Fish that feed on small animals include cleaner fish (these fish feed between the jaws
of larger predatory fish), bullet fish and Balistidae (these eat sea urchins) while seaweed
eating fish include the Pomacentridae (damselfishes). Serranidae
cultivate the seaweed by removing creatures feeding on it (as sea
urchins), and they remove inedible seaweeds. Fish that eat coral
include parrotfish and butterflyfish.
- fish that swim nearby the reef. These include predatory fish
such as pompanos, groupers, Horse
mackerels, certain types of shark, Epinephelus marginatus, barracudas, snappers, ...)
They also include herbivorous and plankton-eating fish. Fish eating
seagrass include Horse mackerel, snapper, Pagellus, Conodon, ...
Fish eating plankton include Caesio, manta ray, chromis,
Holocentridae, pterapogon kauderni, ...
Generally, fish that swim in coral reefs are as colorful as the
reef itself. Examples are the beautiful
parrotfish,
angelfish,
damselfish,
Pomacanthus paru,
Clinidae and
butterflyfish. At night, some change to a less
vivid color. Besides colorful fish matching their environment,
other fish (e.g., predatory and herbivorous fish such as
Lampanyctodes
hectoris,
Holocentridae,
Pterapogon kauderni, ...) as well
as aquatic animals (Comatulida, Crinoidea, Ophiuroidea, ...) emerge
and become active while others rest.
Other fish groups found on coral reefs include
groupers,
grunts and
wrasses. Over 4,000 species of fish inhabit
coral reefs. It has been suggested that the fish species that
inhabit coral reefs are able to coexist in such high numbers
because any free living space is inhabited by the first planktonic
fish larvae that find it in what has been termed "a lottery for
living space".
. Reefs are also home to a large variety of other organisms,
including
sponges,
Cnidarians (which includes some types of corals and
jellyfish),
worms,
crustaceans (including
shrimp,
cleaner shrimp,
spiny lobsters and
crabs),
molluscs (including
cephalopods),
echinoderms (including
starfish, sea urchins and
sea cucumber),
sea
squirts, turtles such as the
sea
turtle, green turtle and hawksbill turtle and
sea snakes. Aside from humans,
mammals are rare on coral reefs, with visiting
cetaceans such as
dolphins being the main exception. A few of these
varied species feed directly on corals, while others graze on algae
on the reef and participate in complex
food
webs.
These other organisms have their part in the food-chain of the
reef. For example, sea urchins eat seaweed, while the
Hawksbill turtle eats sponges. Nudibranchia
eat sponges too, as well as sea anemones. Dotidae and sea slugs eat
seaweed.
A number of invertebrates, collectively called
cryptofauna, inhabit the coral skeletal substrate
itself, either boring into the skeletons (through the process of
bioerosion) or living in pre-existing
voids and crevices. Those animals boring into the rock include
sponges, bivalve molluscs, and
sipunculans. Those settling on the reef include
many other species, particularly crustaceans and
polychaete worms.
Researchers have found evidence of algae dominance in locations of
healthy coral reefs. In surveys done around largely uninhabited US
Pacific islands, algae inhabit a large percentage of surveyed coral
locations. The algae population consists of turf algae,
coralline algae, and
macroalgae.
Darwin's Paradox names the phenomenon in which
coral reefs have high biodiversity in areas that contain few
nutrients. How can such a diverse
ecosystem exist with so few nutrients? The main
reasons for this are:
- Symbiosis between coral and zooxanthellae
- A high nutrient flux
- Very efficient nutrient cycling
- Photosynthetic
efficiency within the ecosystem.
Threats
Human activity may represent the greatest threat to coral reefs. In
particular, coral
mining,
pollution (organic and non-organic/chemical),
over-fishing,
blast fishing and the
digging of
canals and access into islands and
bays are serious threats to these ecosystems. Coral reef also face
high dangers from pollution, diseases, destructive fishing
practices and warming oceans." In order to find answers for these
problems, researchers study the various factors that impact reefs.
The list of factors is long, including the ocean's role as a
carbon dioxide sink, atmospheric
changes,
ultraviolet light,
ocean acidification, biological
virus, impacts of
dust
storms carrying agents to far flung reefs, pollutants,
algal blooms and others. Reefs are threatened
well beyond coastal areas.
Overfishing
The use of
cyanide has been implicated as a
driver of decline. Hughes, et al., (2003), wrote that "with
increased
human population and
improved storage and transport systems, the scale of human impacts
on reefs has grown exponentially. For example, markets for fish and
other
natural resources have become
global, supplying demand for reef resources."
Overfishing (and particularly selective overfishing) results in
excessive growth of organisms that can damage the reef if they
appear in great numbers. For example overfishing of bullet fish,
Balistidae and other natural predators such as lobsters promote the
growth of sea urchins. Also, overpopulation of acanthaster planci,
Drupella, Tapiro, Terpios, and Rhodactis can destroy reefs.
Aquarium fish
Although a few fish species (e.g. Pomacentridae) can reproduce in
aquaria, 95% are collected on the reef. Intense harvesting,
especially in South-East Asia (including Indonesia and the
Philippines), severely damages the reefs. A major catalyst of
cyanide fishing is poverty within
fishing communities. In areas like the Philippines where cyanide is
regularly used, the percentage of the population below the poverty
line is 40%. In such
developing
countries, a fisherman might resort to such practices in order
to protect his family from starvation.
Most, 80–90%, of aquarium fish from the Philippines are captured
with
sodium cyanide. This toxic
chemical is dissolved in sea water and released into fish shelters.
It narcotizes fish, which are then easily captured. However, most
fish collected with cyanide die a few months later from liver
damage. Moreover, non-marketable species die in the field.
Pollution
Pollution from land-based sources is a primary cause of coral reef
degradation throughout the world.
Some nutrients favor species (such as algae, seaweed, ...) that
disrupt the balance of reef communities. Some algae are toxic, and
both plants reduce the levels of sunlight and oxygen, killing
marine organisms such as fish and coral. The addition of nutrients
such as
phosphates and
nitrates are very damaging to reefs. High nitrate
levels are toxic to corals, while phosphates slow down the growth
of coral skeleton. Reefs in close proximity to human populations,
however, will also be faced with local stresses, including poor
water quality from land-based sources of pollution. Poor water
quality has also been shown to encourage the spread of
infectious diseases among corals.
Organic pollutants
Soil runoff
Extensive and poorly managed land development can threaten the
survival of coral reefs. Runoff caused by farming and construction
of roads, buildings, ports, channels, and harbours, can carry soil
laden with carbon, nitrogen, phosphorus, and minerals. This
nutrient-rich water can cause fleshy algae and phytoplankton to
thrive in coastal areas, known as
algal
blooms, which have the potential to create
hypoxic conditions by using all
available oxygen.
Windborne
Barbados dust graph
In addition to local soil runoff, additional soil (sand) is blown
in from other regions.
Dust from the Sahara
moving around the southern periphery of the subtropical ridge moves into the Caribbean and Florida during the warm season as the ridge builds and
moves northward through the subtropical Atlantic.
Dust can
also be attributed to a global transport from the Gobi and Taklamakan deserts across Korea, Japan, and the
Northern Pacific to the
Hawaiian Islands. Since
1970, dust outbreaks have worsened due to periods of drought in
Africa. There is a large variability in dust transport to the
Caribbean and Florida from year to year; however, the flux is
greater during positive phases of the
North Atlantic Oscillation. The
USGS links dust events to a decline in the health of coral reefs
across the Caribbean and Florida, primarily since the 1970s.
Studies
have shown that corals can incorporate dust into their skeletons as
identified from dust from the 1883 eruption of Krakatoa in Indonesia in the annular bands of the reef-building coral
Montastraea annularis
from the Florida reef tract. The relative abundance of
chemical elements, particularly metals, has been used to
distinguish soil derived from volcanic dust from
mineral dust.
Sewage
Another major pollutant is generated by people. Most islanders in
developing countries send sewage unfiltered into the sea. While
most experts now agree that
composting
toilet alongside an
ecological
sanitation approach is appropriate in small island nations,
these countries for the moment prefer to keep using traditional
approaches.
Mines
Inland mines of copper, gold and others form a major center of
pollution. Most of the pollution is simply soil, which ends up in
rivers flowing to the sea and ultimately covers the coral, but
small mineral fractions may also introduce trouble.
Copper, a common industrial pollutant has been shown
to interfere with the
life history and
development of coral polyps.
Non-organic
Leaked oil and chemicals (e.g. from detergents, paints, ...)
flowing into the sea from factory outlets are a key threat.
Chemical
fertilizers (based on ammonium
nitrate) are another pollutant.
Litter is another
important threat, as especially in certain places (eg the Plastic
Vortex), litter kills off many aquatic organisms that are directly
or indirectly beneficial to coral reefs.
Radioactive waste is often dumped by the USA near its military
installations (Mororua, Fangataufa, Johnston Atoll, ... Nuclear
tests (eg at Kwajalein, Bikini, Enewetak) may produce harmful
fallout, yet compared to the other forms of pollution noted, their
impact is small.
Climate change
Any rise in the sea level due to climate change would effectively
ask coral to grow faster to keep up. Also, water temperature
changes can be very disturbing to the coral. This was seen during
the 1998 and 2004
El Niño weather
phenomena, in which
sea surface
temperatures rose well above normal,
bleaching or killing many coral reefs. High
seas surface temperature (SSTs) coupled with high irradiance (light
intensity), triggers the loss of zooxanthellae, a symbiotic algae,
and its dinoflagellate pigmentation in corals causing coral
bleaching. Zooxanthellae provides up to 90% of the energy to the
coral host. Reefs can often recover from bleaching if they are
healthy to begin with and water temperatures cool. However,
recovery may not be possible if CO
2 levels rise to 500
ppm because there may not be enough carbonate ions present. Refer
to Hoegh-Guldberg 1999 for more information.
Warming may also be the basis of a new emerging problem: increasing
coral diseases. Warming (thought to be the main cause of coral
bleaching) weakens corals. In their weakened state, coral is much
more prone to diseases including
Black band disease,
White band disease and
Skeletal Eroding Band. In the event of
a 2°C temperature increase, it is thought that coral is not able to
adapt quickly enough physiologically or genetically In order to
counter the threat of ocean acidification through global warming,
it is stated that a reduction of up to 40% of the current emissions
is needed, and up to 95% by 2050, thus requiring larger emission
reductions than the currently proposed reductions for these dates
by the EU.
Ocean acidification
A related problem to climate change is ocean acidification, which
can be caused by increasing CO
2 emissions.
The decreasing ocean surface pH is of increasing long-term concern
for coral reefs.Increased atmospheric CO
2 increases the
amount of CO
2 dissolved in the oceans. Carbon dioxide
gas dissolved in the ocean reacts with water to form
carbonic acid, resulting in
ocean acidification. Ocean surface pH is
estimated to have decreased from approximately 8.25 to 8.14 since
the beginning of the industrial era, and it is estimated that it
will drop by a further 0.3 - 0.4 units by 2100 as the ocean absorbs
more anthropogenic CO
2. Normally, the conditions for
calcium carbonate production are stable in surface waters since the
carbonate ion is at
supersaturating
concentrations. However, as ocean pH falls, so does the
concentration of this ion, and when carbonate becomes
under-saturated, structures made of calcium carbonate are
vulnerable to dissolution. Research has already found that corals
experience reduced calcification or enhanced dissolution when
exposed to elevated CO
2.
Deep sea bamboo coral supports deep sea life and also may be among
the first organisms to display the effects of changes in ocean
acidification caused by excess carbon dioxide, since they produce
growth rings similar to those of tree and can provide a view of
changes in the condition in the deep sea over time. This coral is
especially long-lived; coral specimens as old as 4,000-year-old
were found at the Monument, giving scientists "4,000 years worth of
information about what has been going on in the deep ocean
interior".
Mangroves and seagrassbeds
Within the last 20 years, once prolific
seagrassbeds and
mangrove forests, which absorb massive
amounts of nutrients and
sediment have been
destroyed. Both the loss of wetlands, mangrove habitats and
seagrassbeds are considered to be significant factors affecting
water quality on inshore reefs.
Coral mining
Coral mining is another threat. Both small-scale harvesting by
villagers, industrial-scale mining by companies are serious
threats. Mining is often done to produce construction material, and
is of particular value as these rocks are up to 50% cheaper than
other rocks (eg from
quarries). The rocks
are ground and mixed with other materials such as cement to make
concrete. Ancient coral used for construction is known as "
coral rag".
Other physical destruction
Dynamite fishing is an extremely
destructive method for gathering fish. Sticks of dynamite,
grenades, or home-made explosives are simply thrown in the water.
This method of fishing kills the fish within the main blast area,
along with many inedible and/or unwanted reef animals. The blast
also kills the corals in the area, eliminating the very structure
of the reef, destroying the habitat for fish and other animals
important for the maintenance of a healthy reef.
Other types of fishing like
muro-ami and
kayakas kills all fish in certain areas,
causing havoc on the ecosystem of the reef.
Boats and ships require an access point into bays and islands to
load/unload cargo/people. For this, often parts of the reef are
chopped away to clear a path. Although this seems but minor
destruction of the reef, potential negative consequences include
altered water circulation and altered tidal patterns, which then
cause a turnaround in the reef's supply of nutrients; sometimes
destroying a great part of the reef.
Fishing boats and other large vessels occasionally run aground on a
reef. Two types of damage can result. Collision damage occurs when
a coral reef is crushed and split by a vessel's hull into multiple
fragments. Scarring occurs when boat propellers tear off the live
coral and expose the skeleton. The physical damage can be noticed
as striations in the reefs.
Mooring also causes considerable damage. To
reduce the (considerable) amount of devastation, boats can use
mooring buoys. They are available in
most major wetparks and marine sanctuaries. Most buoys are of the
Halas Mooring Buoy
System-type.
Construction also takes its toll.
Building directly on the reef can alter water circulation and tides
(which bring the nutrients for the reef). The main reason for
building on reefs (despite possible moisture problems) is simply
the lack of space.
Destruction worldwide
Southeast Asian coral
reefs are at risk from damaging
fishing
practices (such as
cyanide and
blast fishing),
overfishing, sedimentation, pollution and
bleaching. A variety of activities, including education,
regulation, and the establishment of marine protected areas are
under way to protect these reefs.
Indonesia, is home to a third of the world's total corals and
a quarter of its fish species, nearly . Indonesia's coral
reefs are located in the heart of the
Coral Triangle and have fallen victim to
destructive fishing, unregulated tourism, and bleaching due to
climatic changes. Data from 414 reef monitoring stations in 2000
found that only 6% are in excellent condition, while 24% are in
good condition, and approximately 70% are in poor to fair condition
(2003
The Johns Hopkins
University).
On
September 24, 2007, Reef Check (the
world’s largest reef conservation organization) stated that only 5% of Philippines 27,000 square-kilometers of coral reef are in
"excellent condition": Tubbataha Reef, Marine
Park in Palawan, Apo
Island in Negros Oriental, Apo Reef in Puerto Galera, Mindoro, and Verde
Island Passage off Batangas. Philippine coral reefs is second
largest in Asia.
General estimates show approximately 10% world's coral reefs are
already dead.
It is estimated that about 60% of the world's reefs are at risk due
to destructive, human-related activities. The threat to the health
of reefs is particularly strong in
Southeast Asia, where an enormous 80% of
reefs are considered
endangered.
Threatened species
The global standard for recording
threatened marine species is the
IUCN Red List of Threatened Species. This list is the
foundation for marine conservation priorities worldwide. A species
is listed in the threatened category if it is considered to be
critically endangered,
endangered, or
vulnerable. Other categories are
near threatened and
data deficient. By 2008, the
IUCN had assessed all known reef-building corals
species as follows
The
coral triangle
(Indo-Malay-Philippine archipelago) region has the highest number
of reef-building coral species in threatened category as well as
the highest coral species diversity. The loss of coral reef
ecosystems will have devastating effects on many marine species, as
well as on people that depend on reef resources for their
livelihoods.
Protection and restoration
of Ahus Island,
Manus
Province,
Papua New
Guinea, have followed a generations-old practice of
restricting fishing in six areas of their reef lagoon. Their
cultural traditions allow line fishing but not net and spear
fishing. The result is that both the
biomass
and individual fish sizes are significantly larger in these areas
than in places where fishing is completely unrestricted.
Protected areas
Human contact :Touching Reefs, even slightly, can harm them. Boats
and dropped anchors can cause severe damage to these fragile
ecosystems. Frequent human contact kills the reefs over time.Many
governments worldwide take measures to protect their coral
reefs.
Marine Protected Areas have
become increasingly prominent for reef management. MPAs in
Southeast Asia and elsewhere around the world to attempt to promote
responsible
fishery management
and
habitat protection. Much like
national parks and wild life refuges,
MPAs prohibit potentially damaging extraction activities. The
objectives of MPAs are both social and biological, including reef
restoration, aesthetics, increased and protected biodiversity, and
economic benefits. Conflicts surrounding MPAs involve lack of
participation, clashing views and perceptions of effectiveness, and
funding.
Biosphere reserves are other
protected areas that may protect reefs.
Also,
Marine parks, as well as
world heritage sites can protect reefs. World
heritage designation can also play a vital role.
For example the
Chagos
archipelago, Sian
Ka'an, the Great Barrier Reef, Henderson Island,
the Galapagos islands, Belize's Barrier reef and Palau have been
designated as protected by nomination as a world heritage
site.
In
Australia, the Great Barrier Reef is protected by the Great
Barrier Reef Marine Park Authority, and is the subject of much legislation, including
a Biodiversity Action
Plan.
Restoration technologies
Low voltage electrical currents applied through seawater
crystallize dissolved minerals onto steel structures. The resultant
white carbonate (
aragonite) is the same
mineral that makes up natural coral reefs. Corals rapidly colonize
and grow at accelerated rates on these coated structures. The
electrical currents also accelerate formation and growth of both
chemical limestone rock and the skeletons of corals and other
shell-bearing organisms. The vicinity of the anode and cathode
provides a high pH environment which inhibits the growth of
filamentous and fleshy algae, which compete with coral for space.
The increased growth rates cease when the mineral accretion process
stops.
During mineral accretion, the settled corals display an increased
growth rate, and size, and density, but after the process is
complete, growth rate and density return to levels that are
comparable to naturally growing corallites, and are about the same
size or slightly smaller.
In large restoration projects, depending on the type of coral,
placement of propagated
hermatype
coral unto substrate is often done with metal pins,
superglue or
milliput .
Needle and thread can also attach
A-hermatype coral to substrate.
Concrete has also been used to restore large sections of broken
coral reef. Finally, special structures as
reef balls can be placed to provide corals a base
to grow on.
Organizations
Organizations which currently undertake coral reef/atoll
restoration projects using simple methods of
plant propagation:
Organizations which carry out research to better understand the
workings of coral reefs:
Organizations which promote interest, provide knowledge bases about
coral reef survival, and promote activities to protect and restore
coral reefs:
Reefs in the past
Throughout
Earth history, from a few thousand
years after hard skeletons were developed by marine organisms,
there were almost always reefs. The times of maximum development
were in the
Middle Cambrian (513-501
Ma),
Devonian (416-359
Ma) and
Carboniferous (359-299 Ma),
due to Order
Rugosa extinct corals, and
Late Cretaceous (100-65 Ma) and all
Neogene (23 Ma - present), due to Order
Scleractinia corals.
Not all reefs in the past were formed by corals: in the
Early Cambrian (542-513 Ma) resulted from
calcareous
algae and
archaeocyathids (small animals with conical
shape, probably related to
sponges) and in
the
Late Cretaceous (100 - 65 Ma),
when there also existed reefs formed by a group of
bivalves called
rudists; one
of the valves formed the main conical structure and the other, much
smaller valve acted as a cap.
See also
References
Further reading
- Barber, Charles V. and Vaughan R. Pratt. 1998. Poison and
Profit: Cyanide Fishing in the Indo-Pacific. Environment,
Heldref Publications.
- Butler, Steven. 1996. "Rod? Reel? Dynamite? A tough-love aid
program takes aim at the devastation of the coral reefs".
U.S. News and World Report, 25 November
1996.
- Christie, P. 2005a. University of Washington, Lecture. 18 May
2005.
- Christie, P. 2005b. University of Washington, Lecture. 4 May
2005.
- CIA - World Factbook -- Philippines
- Clifton, Julian. 2003. Prospects for Co-Management in
Indonesia's Marine Protected Areas. Marine Policy, 27(5):
389-395.
- Courtney, Catherine and Alan White. 2000. Integrated
Coastal Management in the Philippines. Coastal Management;
Taylor and Francis.
- Fox, Helen. 2005. Experimental Assessment of Coral Reef
Rehabilitation Following Blast Fishing. The Nature Conservancy
Coastal and Marine Indonesia Program. Blackwell Publishers Ltd, Feb
2005.
- Gjertsen, Heidi. 2004. Can Habitat Protection Lead to
Improvements in Human Well-Being? Evidence from Marine
Protected Areas in the Philippines.
- Martin, Glen. 2002. "The depths of destruction Dynamite fishing
ravages Philippines' precious coral reefs". San Francisco
Chronicle, 30 May 2002
- Sadovy, Y.J. Ecological Issues and the Trades in Live Reef
Fishes, Part 1
- USEPA.
- UNEP. 2004. Coral Reefs in the South China Sea. UNEP/GEF/SCS Technical Publication No. 2.
- UNEP. 2007. Coral Reefs Demonstration Sites in the South China
Sea. UNEP/GEF/SCS Technical Publication No. 5.
- UNEP, 2007. National Reports on Coral Reefs in the Coastal
Waters of the South China Sea. UNEP/GEF/SCS Technical Publication No. 11.
External links
- Reports
- Organisations