Environmental issues with coral reefs | Wikipedia audio article


Human impact on coral reefs is significant. Coral reefs are dying around the world. Damaging activities include coral mining,
pollution (organic and non-organic), overfishing, blast fishing, the digging of canals and access
into islands and bays. Other dangers include disease, destructive
fishing practices and warming oceans. Factors that affect coral reefs include the
ocean’s role as a carbon dioxide sink, atmospheric changes, ultraviolet light, ocean acidification,
viruses, impacts of dust storms carrying agents to far-flung reefs, pollutants, algal blooms
and others. Reefs are threatened well beyond coastal areas. Climate change, such as warming temperatures,
causes coral bleaching, which if severe kills the coral. In 2008, a worldwide study estimated that
19% of the existing area of coral reefs has already been lost, and that a further 17%
is likely to be lost over the subsequent 10–20 years. Only 46% of the world’s reefs could be currently
regarded as in good health and about 60% of the world’s reefs may be at risk due to destructive,
human-related activities. The threat to the health of reefs is particularly
strong in Southeast Asia, where 80% of reefs are endangered. By the 2030s, 90% of reefs are expected to
be at risk from both human activities and climate change; by 2050, it is predicted that
all coral reefs will be in danger.==Issues=====Competition===
In the Caribbean Sea and tropical Pacific ocean, direct contact between coral and common
seaweeds causes bleaching and death of coral tissue via allelopathic competition. The lipid-soluble extracts of seaweeds that
harmed coral tissues, also produced rapid bleaching. At these sites, bleaching and mortality was
limited to areas of direct contact with seaweed or their extracts. The seaweed then expanded to occupy the dead
coral’s habitat. However, as of 2009, only 4% of coral reefs
worldwide had more than 50% algal coverage which means that there are no recent global
trend towards algal dominance over coral reefs.Competitive seaweed and other algae thrive in nutrient-rich
waters in the absence of sufficient herbivorous predators. Herbivores include fish such as parrotfishs,
surgeonfishes, tangs and unicornfishes.===Predation===Overfishing, particularly selective overfishing,
can unbalance coral ecosystems by encouraging the excessive growth of coral predators. Predators that eat living coral, such as the
crown-of-thorns starfish, are called corallivores. Coral reefs are built from stony coral, which
evolved with large amounts of the wax cetyl palmitate in their tissues. Most predators find this wax indigestible. The crown-of-thorns starfish is a large (up
to one meter) starfish protected by long, venomous spines. Its enzyme system dissolves the wax in stony
corals, and allows the starfish to feed on the living animal. Starfish face predators of their own, such
as the giant triton sea snail. However, the giant triton is valued for its
shell and has been over fished. As a result, crown-of-thorns starfish populations
can periodically grow unchecked, devastating reefs.===Fishing practices===
Although some marine aquarium fish species can reproduce in aquaria (such as Pomacentridae),
most (95%) are collected from coral reefs. Intense harvesting, especially in maritime
Southeast Asia (including Indonesia and the Philippines), damages the reefs. This is aggravated by destructive fishing
practices, such as cyanide and blast fishing. Most (80–90%) aquarium fish from the Philippines
are captured with sodium cyanide. This toxic chemical is dissolved in sea water
and released into areas where fish shelter. It narcotizes the fish, which are then easily
captured. However, most fish collected with cyanide
die a few months later from liver damage. Moreover, many non-marketable specimens die
in the process. It is estimated that 4,000 or more Filipino
fish collectors have used over 1,000,000 kilograms (2,200,000 lb) of cyanide on Philippine reefs
alone, about 150,000 kg per year. A major catalyst of cyanide fishing is poverty
within fishing communities. In countries like the Philippines that regularly
employ cyanide, more than thirty percent of the population lives below the poverty line.Dynamite
fishing is another destructive method for gathering fish. Sticks of dynamite, grenades, or home-made
explosives are detonated in the water. This method of fishing kills the fish within
the main blast area, along with many unwanted reef animals. The blast also kills the corals in the area,
eliminating the reef’s structure, destroying habitat for the remaining fish and other animals
important for reef health. Muroami is the destructive practice of covering
reefs with nets and dropping large stones onto the reef to produce a flight response
among the fish. The stones break and kill the coral. Muroami was generally outlawed in the 1980s.Fishing
gear damages reefs via direct physical contact with the reef structure and substrate. Gill nets, fish traps, and anchors break branching
coral and cause coral death through entanglement. When fishermen drop lines by coral reefs,
the lines entangle the coral. The fisher cuts the line and abandons it,
leaving it attached to the reef. The discarded lines abrade coral polyps and
upper tissue layers. Corals are able to recover from small lesions,
but larger and recurrent damage complicates recovery. Bottom dragging gear such as beach seines
can damage corals by abrasion and fracturing. A beach seine is a long net about 150 meters
(490 ft) with a mesh size of 3 centimeters (1.2 in) and a weighted line to hold the net
down while it is dragged across the substrate and is one of the most destructive types of
fishing gear on Kenya’s reefs.Bottom trawling in deep oceans destroys cold–water and deep–sea
corals. Historically, industrial fishers avoided coral
because their nets would get caught on the reefs. In the 1980s, “rock–hopper” trawls attached
large tires and rollers to allow the nets to roll over rough surfaces. Fifty-five percent of Alaskan cold–water
coral that was damaged by one pass from a bottom trawl had not recovered a year later. Northeast Atlantic reefs bear scars up to
4 kilometers (2.5 mi) long. In Southern Australia, 90 percent of the surfaces
on coral seamounts are now bare rock. Even in the Great Barrier Reef World Heritage
Area, seafloor trawling for prawns and scallops is causing localized extinction of some coral
species. “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.”===
Marine pollution===Reefs in close proximity to human populations
are subject to poor water quality from land- and marine-based sources. In 2006 studies suggested that approximately
80 percent of ocean pollution originates from activities on land. Pollution arrives from land via runoff, the
wind and “injection” (deliberate introduction, e.g., drainpipes). Runoff brings with it sediment from erosion
and land-clearing, nutrients and pesticides from agriculture, wastewater, industrial effluent
and miscellaneous material such as petroleum residue and trash that storms wash away. Some pollutants consume oxygen and lead to
eutrophication, killing coral and other reef inhabitants.An increasing fraction of the
global population lives in coastal areas. Without appropriate precautions, development
(e.g., buildings and paved roads) increases the fraction of rainfall and other water sources
that enter the ocean as runoff by decreasing the land’s ability to absorb it.Pollution
can introduce pathogens. For example, Aspergillus sydowii has been
associated with a disease in sea fans, and Serratia marcescens, has been linked to the
coral disease white pox.Reefs in close proximity to human populations can be faced with local
stresses, including poor water quality from land-based sources of pollution. Copper, a common industrial pollutant has
been shown to interfere with the life history and development of coral polyps. In addition to runoff, wind blows material
into the ocean. This material may be local or from other regions. For example, dust from the Sahara moves to
the Caribbean and Florida. Dust also blows from the Gobi and Taklamakan
deserts across Korea, Japan, and the Northern Pacific to the Hawaiian Islands. Since 1970, dust deposits have grown due to
drought periods in Africa. Dust transport to the Caribbean and Florida
varies from year to year with greater flux during positive phases of the North Atlantic
Oscillation. The USGS links dust events to reduced health
of coral reefs across the Caribbean and Florida, primarily since the 1970s. Dust from the 1883 eruption of Krakatoa in
Indonesia appeared in the annular bands of the reef-building coral Montastraea annularis
from the Florida Reeftract.Sediment smothers corals and interferes with their ability to
feed and reproduce. Pesticides can interfere with coral reproduction
and growth. There is evidence that chemicals in sunscreens
contribute to coral bleaching by lowering the resistance of zooxanthellae to viruses.====Nutrient pollution====Nutrient pollution, particularly nitrogen
and phosphorus can cause eutrophication, upsetting the balance of the reef by enhancing algal
growth and crowding out corals. This nutrient–rich water can enable blooms
of fleshy algae and phytoplankton to thrive off coasts. These blooms can create hypoxic conditions
by using all available oxygen. Biologically available nitrogen (nitrate plus
ammonia) needs to be below 1.0 micromole per liter (less than 0.014 parts per million of
nitrogen), and biologically available phosphorus (orthophosphate plus dissolved organic phosphorus)
needs to be below 0.1 micromole per liter (less than 0.003 parts per million of phosphorus). In addition concentrations of chlorophyll
(in the microscopic plants called phytoplankton) needs to be below 0.5 parts per billion. Both plants also obscure sunlight, killing
both fish and coral. High nitrate levels are specifically toxic
to corals, while phosphates slow down skeletal growth. Excess nutrients can intensify existing disease,
including potentially doubling the spread of Aspergillosis, a fungal infection that
kills soft corals such as sea fans, and increasing yellow band disease, a bacterial infection
that kills reef-building hard corals by fifty percent.====Air pollution====A study released in April 2013 has shown that
air pollution can also stunt the growth of coral reefs; researchers from Australia, Panama
and the UK used coral records (between 1880 and 2000) from the western Caribbean to show
the threat of factors such as coal-burning coal and volcanic eruptions. The researchers state that the study signifies
the first time that the relationship between air pollution and coral reefs has been elucidated,
while former chair of the Great Barrier Reef Marine Park Authority Ian McPhail referred
to the report as “fascinating” upon the public release of its findings.===Marine debris===Marine debris is any solid object that enters
coastal and ocean waters. Debris may arrive directly from a ship or
indirectly when washed out to sea via rivers, streams, and storm drains. Human-made items tend to be the most harmful
such as plastics (from bags to balloons, hard hats to fishing line), glass, metal, rubber
(millions of waste tires), and even entire vessels.Plastic debris kills several reef
species. Derelict (abandoned) fishing nets and other
gear—often called “ghost nets” because they still catch fish and other marine life despite
being abandoned—can entangle and kill reef organisms and break or damage reefs. Even remote reef systems suffer the effects
of marine debris. Reefs in the Northwestern Hawaiian Islands
are particularly prone to the accumulation of marine debris because of their central
location in the North Pacific Gyre. From 2000 to 2006, NOAA and partners removed
over 500 tons of marine debris there.===Dredging===Dredging operations are sometimes completed
by cutting a path through a coral reef, directly destroying the reef structure and killing
any organisms that live on it. Operations that directly destroy coral are
often intended to deepen or otherwise enlarge shipping channels or canals, due to the fact
that in many areas, removal of coral requires a permit, making it more cost-effective and
simple to avoid coral reefs if possible. Dredging also releases plumes of suspended
sediment, which can settle on coral reefs, damaging them by starving them of food and
sunlight. Continued exposure to dredging spoil has been
shown to increase rates of diseases such as white syndrome, bleaching and sediment necrosis
among others. A study conducted in the Montebello and Barrow
Islands showed that the number of coral colonies with signs of poor health more than doubled
in transects with high exposure to dredging sediment plumes.===Sunscreen===
Sunscreen enters the ocean through wastewater systems when it is washed off and from swimmers
and divers. Some 14,000 tons of sunscreen ends up in the
ocean each year, with 4000 to 6000 tons entering reef areas annually. There is an estimate that 90% of snorkeling
and diving tourism is concentrated on 10% of the world’s coral reefs, meaning that popular
reefs are especially vulnerable to sunscreen exposure. Certain formulations of sunscreen are a serious
danger to coral health. The common sunscreen ingredient oxybenzone
causes coral bleaching and has an impact on other marine fauna.In Akumal, Mexico, visitors
are warned not to use sunscreen and are kept out of some areas to prevent damage to the
coral. In several other tourist destinations, authorities
recommend the use of sunscreens prepared with the naturally occurring chemicals titanium
dioxide or zinc oxide, or suggest the use of clothing rather than chemicals to screen
the skin from the sun.===Climate change===Rising sea levels due to climate change requires
coral to grow to stay close enough to the surface to continue photosynthesis. Also, water temperature changes or disease
of the coral can induce coral bleaching, as happened during the 1998 and 2004 El Niño
years, in which sea surface temperatures rose well above normal, bleaching and killing many
reefs. Bleaching may be caused by different triggers,
including High sea surface temperature (SST), pollution, or other diseases. SST coupled with high irradiance (light intensity),
triggers the loss of zooxanthellae, a symbiotic single cell algae that gives the coral its
color and the coral’s dinoflagellate pigmentation, which turns the coral white when it is expelled,
which can kill the coral. Zooxanthellae provide up to 90% of their hosts’
energy supply. Healthy reefs can often recover from bleaching
if water temperatures cool. However, recovery may not be possible if CO2
levels rise to 500 ppm because concentrations of carbonate ions may then be too low.Warming
seawater may also encourage an emerging problem: coral disease. Weakened by warm water, coral is much more
prone to diseases including black band disease, white band disease and skeletal eroding band. If global temperatures increase by 2 °C during
the twenty-first century, coral may not be able to adapt quickly enough.Warming seawater
is also expected to cause migrations in fish populations to compensate for the change. This puts coral reefs and their associated
species at risk of invasion and may cause their extinction if they are unable to compete
with the invading populations.A 2010 report by the Institute of Physics predicts that
unless the national targets set by the Copenhagen Accord are amended to eliminate loopholes,
then by 2100 global temperatures could rise by 4.2 °C and result in an end to coral reefs.===Ocean acidification===Ocean acidification results from increases
in atmospheric carbon dioxide. Oceans absorb around one–third of the increase. The dissolved gas reacts with the water to
form carbonic acid, and thus acidifies the ocean. This decreasing pH is another issue for coral
reefs.Ocean surface pH is estimated to have decreased from about 8.25 to 8.14 since the
beginning of the industrial era, and a further drop of 0.3–0.4 units is expected. This drop has made it so the amount of hydrogen
ions have increased by 30%. Before the industrial age the conditions for
calcium carbonate production were typically stable in surface waters since the carbonate
ion is at supersaturated concentrations. However, as the ionic concentration falls,
carbonate becomes under-saturated, making calcium carbonate structures vulnerable to
dissolution. Corals experience reduced calcification or
enhanced dissolution when exposed to elevated CO2. This causes the skeletons of the corals to
weaken, or even not be made at all.Bamboo coral is a deep water coral which produces
growth rings similar to trees. The growth rings illustrate growth rate changes
as deep sea conditions change, including changes due to ocean acidification. Specimens as old as 4,000 years have given
scientists “4,000 years worth of information about what has been going on in the deep ocean
interior”. Rising carbon dioxide levels could confuse
brain signaling in fish. In 2012, researchers reported on their results
after studying the behaviour of baby clown and damselfishes for several years in water
with elevated levels of dissolved carbon dioxide, in line with what may exist by the end of
the century. They found that the higher carbon dioxide
disrupted a key brain receptor in the fish, interfering with neurotransmitter functions. The damaged central nervous systems affected
fish behaviour and diminishing their sensory capacity to a point “likely to impair their
chances of survival”. The fishes were less able to locate reefs
by smell or “detect the warning smell of a predator fish”. Nor could they hear the sounds made by other
reef fish, compromising their ability to locate safe reefs and avoid dangerous ones. They also lost their usual tendencies to turn
to the left or right, damaging their ability to school with other fish.===Disease===
Disease is a serious threat to many coral species. The diseases of coral may consist of bacterial,
viral, fungal, or parasitic infections. Due to stressors like climate change and pollution,
coral can become more vulnerable to diseases. Some examples of coral disease are Vibrio,
white syndrome, white band, rapid wasting disease, and many more. These diseases have different effects on the
corals, ranging from damaging and killing individual corals to wiping out entire reefs.In
the Caribbean, white band disease is one of the primary causes for the death of over eighty
percent of Staghorn and Elkhorn coral (Reef Resilience). It is a disease that can destroy miles of
coral reef fast. A disease such as white plague can spread
over a coral colony by a half an inch a day. By the time the disease has fully taken over
the colony, it leaves behind a dead skeleton. Dead standing coral structures are what most
people see after disease has taken over a reef. Recently, the Florida Reef Tract in the United
States has been plagued by a stony coral tissue loss disease. The disease was first identified in 2014 and
as of 2018 has been reported in every part of the reef except the lower Florida Keys
and the Dry Tortugas. The cause of the disease is unknown but is
thought to be caused by bacteria and be transmitted through direct contact and water circulation. This disease event is unique due to its large
geographic range, extended duration, rapid progression, high rates of mortality and the
number of species affected.===Other issues===Within the last 20 years, once-prolific seagrass
meadows and mangrove forests, which absorb massive amounts of nutrients and sediment,
have been destroyed. Both the loss of wetlands, mangrove habitats
and seagrass meadows affect the water quality of inshore reefs.Coral mining is another threat. Both small scale harvesting by villagers and
industrial scale mining by companies are serious threats. Mining is usually done to produce construction
material which is valued as much as 50% cheaper than other rocks, such as from quarries. The rocks are ground and mixed with other
materials, like cement to make concrete. Ancient coral used for construction is known
as coral rag. Building directly on the reef also takes its
toll, altering water circulation and the tides which bring the nutrients to the reef. The pressing reason for building on reefs
is simply lack of space. Boats and ships require access points into
bays and islands to load and unload cargo and people. For this, parts of reefs are often chopped
away to clear a path. Negative consequences can include altered
water circulation and altered tidal patterns which can disrupt the reef’s nutrient supply;
sometimes destroying a great part of the reef. Fishing vessels and other large boats 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. Mooring causes damage which can be reduced
by using mooring buoys. Buoys can attach to the seafloor using concrete
blocks as weights or by penetrating the seafloor, which further reduces damage. Also, reef docks can be used to move over
goods from large, seagoing vessels to small, flat-bottomed vessels. Coral in Taiwan is being threatened by the
influx of human population growth. Since 2007, several local environmental groups
conducted research and found that much of the coral populations are being affected by
untreated sewage, an influx of tourists taking corals for souvenirs, without fully understanding
the destructive impact on the coral’s ecological system. Researchers reported to the Taiwanese government
that many coral populations have turned black in the southeast coast of Taiwan. Potentially, this could lead to loss of food
supply, medicinal sources and tourism due to the breakdown of the food chain.==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 845 known
reef-building corals species, marking 27% as Threatened 20% as near threatened and 17%
as data deficient.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.==Issues by region=====Australia===The Great Barrier Reef is the world’s largest
coral reef system. The reef is located in the Coral Sea and a
large part of the reef is protected by the Great Barrier Reef Marine Park. Particular environmental pressures include
surface runoff, salinity fluctuations, climate change, cyclic crown-of-thorns outbreaks,
overfishing, and spills or improper ballast discharge. According to the 2014 report of the Government
of Australia’s Great Barrier Reef Marine Park Authority (GBRMPA), climate change is the
most significant environmental threat to the Great Barrier Reef. As of 2018, 50% of the coral on the Great
Barrier Reef has been lost.===Southeast Asia===Southeast Asian coral reefs are at risk from
damaging fishing practices (such as cyanide and blast fishing), overfishing, sedimentation,
pollution and bleaching. Activities including education, regulation
and the establishment of marine protected areas help protect these reefs.====Indonesia====
Indonesia is home to one-third of the world’s coral reefs, with coral that covers nearly
85,000 square kilometres (33,000 sq mi) and is home to one-quarter of its fish species. Indonesia’s coral reefs are located in the
heart of the Coral Triangle and have fallen victim to destructive fishing, tourism and
bleaching. Data from LIPI in 1998 found that only 7 percent
is in excellent condition, 24 percent is in good condition and approximately 69 percent
is in poor-to-fair condition. According to one source, Indonesia will lose
70 percent of its coral reef by 2050 if restoration action does not occur.====Philippines====
In 2007, Reef Check, the world’s largest reef conservation organization, stated that only
5% of Philippines 27,000 square kilometres (10,000 sq mi) 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 Asia’s second largest.====Taiwan====
Coral reefs in Taiwan are being threatened by human population growth. Many corals are affected by untreated sewage
and souvenir-hunting tourists, not knowing that this practice destroys habitat and causes
disease. Many corals have turned black from disease
off Taiwan’s southeast coast.===Caribbean===
Coral disease was first recognized as a threat to Caribbean reefs in 1972 when black band
disease was discovered. Since then diseases have been occurring with
higher frequency.It has been estimated that 50% of the Caribbean sea coral cover has disappeared
since the 1960s. According to a United Nations Environment
Program report, the Caribbean coral reefs might face extirpation in next 20 years due
to population expansion along the coast lines, overfishing, the pollution of coastal areas,
global warming, and invasive species.In 2005, the Caribbean lost about 50% of its reef in
one year due to coral bleaching. The warm water from Puerto Rico and the Virgin
Islands travelled south to cause this coral bleaching.====Jamaica====Jamaica is the third largest Caribbean island. The Caribbean’s coral reefs will cease to
exist in 20 years if a conservation effort is not made. In 2005, 34 percent of Jamaica’s coral reefs
were bleached due to rising sea temperatures. Jamaica’s coral reefs are also threatened
by overfishing, pollution, natural disasters, and reef mining. In 2009, researchers concluded that many of
the corals are recovering very slowly.====United States====
Southeastern Florida’s reef track is 300 miles long. Florida’s coral reefs are currently undergoing
an unprecedented stony coral tissue loss disease. The disease covers a large geographic range
and affects many species of coral. In January 2019, science divers confirmed
that the outbreak of stony coral tissue that extends south and west of Key West. In December 2018, Disease was spotted at Maryland
Shoals, near the Saddleback Keys. By mid January 5 more sites between American
Shoal and Eastern Dry Rocks were confirmed diseased.Puerto Rico is home to over 5,000
square kilometers of shallow coral reef ecosystems. Puerto Rico’s coral reefs and associated
ecosystems have an average economic value of nearly $1.1 billion per year. The U.S. Virgin Islands’ coral reefs and
associated ecosystems have an average economic value of $187 million per year. Hawaii’s coral reefs are a major factor in
Hawaii’s $800 million a year marine tourism and are being affected negatively by coral
bleaching and increased sea surface temperatures, which in turn leads to coral reef diseases. The first large-scale coral bleaching occurred
in 1996 and in 2004 it was found that the sea surface temperatures had been steadily
increasing and if this pattern continues, bleaching events will occur more frequently
and severely

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