Overblog Suivre ce blog
Editer l'article Administration Créer mon blog
20 novembre 2013 3 20 /11 /novembre /2013 10:46

However, fertiliser and byproducts from sugar cane harvesting methods form a component of surface runoff into the Great Barrier Reef lagoon.[12][13] Principal agricultural activity is sugar cane farming in the wet tropics and cattle grazing in the dry tropics regions. Both are considered significant factors affecting water quality.[13] ASUS A8H CPU Fan

Copper, a common industrial pollutant in the waters of the Great Barrier Reef, has been shown to interfere with the development of coral polyps.[14] Flood plumes are flooding events associated with higher levels of nitrogen and phosphorus.[15] In February 2007, due to a monsoonal climate system, SONY UDQFRZH13CF0 CPU Fan

plumes of sediment runoff have been observed reaching to the outmost regions of the reef.[16]

Runoff is especially concerning in the region south of Cairns, as it receives over 3000 mm of rain per year and the reefs are less than 30 kilometres (19 mi) away from the coastline.[17] Farm run off is polluted as a result of overgrazing and excessive fertiliser and pesticide use. HP COMPAQ 2510P CPU Fan

Mud pollution has increased by 800% and inorganic nitrogen pollution by 3,000% since the introduction of European farming practices on the Australian landscape. This pollution has been linked to a range of very significant risks to the reef system, including intensified outbreaks of the coral-eating Crown of Thorns Starfish which contributed to a loss of 66% of live coral cover on sampled reefs in 2000.[18] APPLE 661-4951 CPU Fan

It is thought that the mechanism behind excess nutrients affecting the reefs is due to increased light and oxygen competition from algae,[9] but unless herbivory is unusually low, this will not create a phase shift from the Great Barrier Reef being primarily made up of coral to being primarily made up of algae.[19] HP Pavilion dv6-3034ca CPU Fan

It has been suggested that poor water quality due to excess nutrients encourages the spread of infectious diseases among corals.[20] In general, the Great Barrier Reef is considered to have low incidences of coral diseases.[21] Skeletal Eroding Band, a disease of bony corals caused by the protozoan Halofolliculina corallasiaHP G56-126NR CPU Fan

affects 31 species of corals from six families on the reef.[22] The long-term monitoring program has found an increase in incidences of coral disease in the period 1999-2002, although they dispute the claim that on the Great Barrier Reef, coral diseases are caused by anthropogenic pollution.[23] Compaq Presario C556CA CPU Fan

Elevated nutrient concentrations result in a range of impacts on coral communities and under extreme conditions can result in a collapse. It also affects coral by promoting phytoplankton growth which increases the number of filter feeding organisms that compete for space. SONY Vaio VGN-NR360E CPU Fan

Excessive inputs of sediment from land to coral can lead to reef destruction through burial, disruption of recruitment success or deleterious community shifts. Sediments affect coral by smothering them when particles settle out, reducing light availability and potentially reducing photosynthesis and growth. HP Pavilion dv5170us CPU Fan

Coral reefs exist in seawater salinities from 25 to 42%. Salinity impacts to corals are increased by other flood-related stresses.[9]

The Australian and Queensland Governments have committed to act to protect the reef,[24] and water quality monitoring programmes are in place.[6] SONY Vaio VPC-EE3WFX/WI CPU Fan

However, theWorld Wildlife Fund has criticised that progress against these commitments has been slow, saying that as many as 700 reefs are at risk from sediment runoff.

Most people believe that the most significant threat to the status of the Great Barrier Reef and of the planet's other tropical reef ecosystems is climate change, consisting chiefly of global warming and the El Niño effect.[ HP G56-126NR CPU Fan

and turn colourless, revealing their white calcium carbonate skeletons, under the stress of waters that remain too warm for too long. At this stage the coral is still alive, and if the water cools, the coral can regain its zooxanthellae.[27] If the water does not cool within about a month, the coral will die of starvation. Australia experienced its warmest year on record in 2005. HP 3MLX8TATP20 CPU Fan

Abnormally high sea temperatures during the summer of 2005-2006 have caused massive coral bleaching in the Keppel Islandgroup.

Most scientists studying the issue believe that climate change poses a massive threat to the future of the Great Barrier Reef. SONY Vaio VGN-NW240F/S CPU Fan

A draft report by the UN Intergovernmental Panel on Climate Change, the world's preeminent gathering of climate scientists, states that the Great Barrier Reef is at grave risk and will be "functionally extinct" by 2030, warning that coral bleaching will likely become an annual occurrence.[28] SONY Vaio VPC-EB1Z0E/B CPU Fan

However, a few scientists hold that coral bleaching may in some cases be less of a problem than the mainstream believes. Professor Ridd, from James Cook University in Townsville was quoted in The Australian (a conservative newspaper) as saying; "They are saying bleaching is the end of the world, but when you look into it, that is a highly dubious proposition".Compaq Presario CQ60-514NR CPU Fan

Research by scientist Ray Berkelmans "... has documented astonishing levels of recovery on the Keppel outcrops devastated by bleaching in 2006." [29] A related article in The Australian newspaper goes on to explain that; "Those that expel their zooxanthellae have a narrow opening to recolonise with new, temperature-resistant algae before succumbing. Toshiba Satellite X205-S9800 CPU Fan

In the Keppels in 2006, Berkelmans and his team noticed that the dominant strain of zooxanthellae changed from light and heat-sensitive type C2, to more robust types D and C1." [30]

Nevertheless, most coral reef researchers anticipate severely negative effects from climate change already occurring, and potentially disastrous effects as climate change worsens. ASUS G2P CPU Fan

The future of the Reef may well depend on how much the planet's climate changes, and thus, on how high atmospheric greenhouse gas concentration levels are allowed to rise. On 2 September 2009, a report by the Australian Great Barrier Reef Marine Park Authorityrevealed that if carbon dioxide levels reached 450 parts per million corals and reef habitats will be highly vulnerable.Compaq Presario CQ60-430SA CPU Fan

If carbon dioxide levels are managed at or below 380 parts per million they will be only moderately vulnerable and the reefs will remain coral-dominated.[31]

Global warming may have triggered the collapse of reef ecosystems throughout the tropics. Increased global temperatures are thought by some to bring more violent tropical storms, DELL BFB0505HA CPU Fan

but reef systems are naturally resilient and recover from storm battering. Most people agree that an upward trend in temperature will cause much more coral bleaching;[25][32] others suggest that while reefs may die in certain areas, other areas will become habitable for corals, and new reefs will form.[33] HP Pavilion dv5-1272et CPU Fan

However, the rate at which the mass bleaching events occur is estimated to be much faster than reefs can recover from, or adjust to.[27]

However, Kleypas et al. in their 2006 report suggest that the trend towards ocean acidification indicates that as the sea's pH decreases, corals will become less able to secrete calcium carbonate.[34] Toshiba AB7005HX-SB3 CPU Fan

In 2009, a study showed that Porites corals, the most robust on the Great Barrier Reef, have slowed down their growth by 14.2% since 1990. It suggested that the cause was heat stress and a lower availability of dissolved calcium to the corals.[35]

Climate change and global warming are one of the greatest threats to the reef.[25] Toshiba Satellite A500-18T CPU Fan

A temperature rise of between two and three degrees Celsius would result in 97% of the Great Barrier Reef being bleached every year.[36] Reef scientist Terry Done has predicted that a one-degree rise in global temperature would result in 82% of the reef bleached, two degrees resulting in 97% and three degrees resulting in "total devastation".[37HP Pavilion dv5-2135dx CPU Fan

] A predictive model based on the 1998 and 2002 bleaching events has concurred that a temperature rise of three degrees would result in total coral mortality.[38]

Climate change has implications for other forms of life on the Great Barrier Reef as well - some fish's preferred temperature range lead them to seek new areas to live, ASUS EEE PC 1201NL CPU Fan

thus causing chick mortality in seabirds that prey on the fish. Also, in sea turtles, higher temperatures mean that the sex ratio of their populations will change, as the sex of sea turtles is determined by temperature. The habitat of sea turtles will also shrink.

The Crown-of-Thorns Starfish is a coral reef predator which preys on coral polyps by climbing onto them, SONY Vaio VGN-NW240D/T CPU Fan

extruding its stomach over them, and releasing digestive enzymes to absorb the liquified tissue. An individual adult of this species can eat up to six square metres of living reef in a single year.[39] Geological evidence suggests that the Crown-of-Thorns Starfish has been part of the Great Barrier Reef's ecology for "at least several thousand years", Compaq Presario CQ60-418DX CPU Fan

but there is no geological evidence for Crown-of-Thorns outbreaks.[40] Large outbreaks of these starfish can devastate reefs. In 2000, an outbreak contributed to a loss of 66% of live coral cover on sampled reefs in a study by the CRC Reefs Research Centre.[18] Although large outbreaks of these starfish are believed to occur in natural cycles, SONY Vaio VGN-NW240D CPU Fan

human activity in and around the Great Barrier Reef can worsen the effects. Reduction of water quality associated with agriculture can cause the crown-of-thorns starfish larvae to thrive. Overfishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of crown-of-thorns starfish.[41] SONY VGN-BX197XP CPU Fan

The CRC Reef Research Centre defines an outbreak as when there are more than 30 adult starfish in an area of one hectare.

The unsustainable overfishing of keystone species, such as the Giant Triton and sharks, can cause disruption to food chains vital to life on the reef. Fishing also impacts the reef through increased pollution from boats, Toshiba Satellite L645D-S4056 CPU Fan

by-catch of unwanted species (such as dolphins and turtles) and reef habitat destruction fromtrawling, anchors and nets.[43] Overfishing of herbivore populations can cause algal growths on reefs. The Batfish Platax pinnatus has been observed to significantly reduce algal growths in studies simulating overfishing.[44] Toshiba AB7805HX-GB3 CPU Fan

Sharks are fished for their meat, and when they are part of bycatch, it is common to kill the shark and throw it overboard, as there is a belief that they interfere with fishing.[45] As of 1 July 2004, approximately one-third of the Great Barrier Reef Marine Park is protected from species removal of any kind, including fishing, without written permission.[46] However, illegal poaching is not unknown in these no-take zones. Toshiba Satellite L500-208 CPU Fan

Shipping accidents continue to be perceived as a threat, as several commercial shipping routes pass through the Great Barrier Reef. The GBRMPA estimates that about 6000 vessels greater than 50 metres (164 ft) in length use the Great Barrier Reef as a route.[47] From 1985 to 2001, 11 collisions and 20 groundings occurred along the Great Barrier Reef shipping route, HP 535441-001 CPU Fan

with human error identified as the leading cause of shipping accidents.[48]

Reef pilots have stated that they consider the reef route safer than outside the reef in the event of mechanical failure, since a ship can sit safely while being repaired.[49] The inner route is used by 75% of all ships that travel over the Great Barrier Reef.[47] Toshiba Satellite P100-444 CPU Fan

As of 2007, over 1,600 known shipwrecks have occurred in the Great Barrier Reef region.[50]

Waste and foreign species discharged from ships in ballast water (when purging procedures are not followed) are a biological hazard to the Great Barrier Reef.[51] Tributyltin (TBT) compounds found in some antifouling paint on ship hulls leaches into seawater and is toxic to marine organisms and humans; as of 2002, efforts are underway to restrict its use.[52] HP Pavilion dv7-3114eo CPU Fan

In April 2010, the bulk coal carrier Shen Neng 1 ran aground on the Great Barrier Reef, causing the largest grounding scar to date. The spill caused damage to a 400,000sqm section of the Great Barrier Reef and the use of oil dispersant resulted in oil spreading to reef islands 25 km away. HP Mini 110-1125SA CPU Fan

It was suspected that the Great Barrier Reef is the cap to an oil trap, after a 1923 paper suggested that it had the right rock formation to support "oilfields of great magnitude". After the Commonwealth Petroleum Search Subsidies Act of 1957, exploration activities increased in Queensland, including a well drilled atWreck Island in the southern Great Barrier Reef in 1959.[54] HP KSB06105HA CPU Fan

In the 1960s, drilling for oil and gas was investigated throughout the Great Barrier Reef,[55][56] by seismic and magnetic methods in the Torres Strait, along "the eastern seaboard of Cape York to Princess Charlotte Bay" and along the coast from Cooktown toFraser Island. Compaq Presario CQ60-210eo CPU Fan

In the late 1960s, more exploratory wells were drilled near Wreck Island in the Capricorn Channel, and near Darnley Island in the Torres Strait, but "all results were dry".[54]

In 1970, responding to concern about oil spills such as the Torrey Canyon, two Royal Commissions were ordered "into exploratory and production drilling for petroleum in the area of the Great Barrier Reef".HP Pavilion dv7-2250sf CPU Fan

After the Royal Commissions, the federal and state governments ceased allowing petroleum drilling on the Great Barrier Reef.[4][57] A study in 1990 concluded that the reef is too young to contain oil reserves.[58] Oil drilling remains prohibited on the Great Barrier Reef, yet oil spills due to shipping routes are still a threat to the reef system, HP 434678-001 CPU Fan

with a total of 282 oil spills between 1987-2002.

Tropical cyclones are a cause of ecological disturbance to the Great Barrier Reef. The types of damage caused by tropical cyclones to the Great Barrier Reef is varied, including fragmentation, sediment plumes, and decreasing salinity following heavy rains (Tropical Cyclone Joy). HP G60-230us CPU Fan

The patterns of reef damage are similarly 'patchy'. From 1910–1999, 170 cyclones' paths came near or through the Great Barrier Reef. Most cyclones pass through the Great Barrier Reef within a day.[59] In general, compact corals such as Porites fare better than branching corals under cyclone conditions. HP Pavilion dv6365us CPU Fan

The major damage caused by Tropical Cyclone Larry was to underlying reef structures, and breakage and displacement of corals, which is overall consistent with previous tropical cyclone events.[60] Severe tropical cyclones hit the Queensland coast every 200 to 300 years;[21] however, HP 535439-001 CPU Fan

during the period 1969–1999 most cyclones in the region were very weak – category one or two on the Australian Bureau of Meteorology scale.[59]

On 2 February 2011, Severe Tropical Cyclone Yasi struck northern Queensland and caused severe damage to a stretch of hundreds of kilometres within the Great Barrier Reef. COMPAQ 6910c CPU Fan

The corals could take a decade to recover fully. Cyclone Yasi had wind speeds of 290 kilometers per hour. HP G62-110SO CPU Fan

On the second day of the 2013 round of the biennial training exercise 'Talisman Saber', in which 28,000 US and Australian military personnel conduct joint activities over a three-week period,four unarmed bombs were dropped into the Great Barrier Reef by two US AV-8B Harrier jets that were unable to land with the weight of the weapons. IBM Lenovo IdeaPad G510 CPU Fan

To minimize potential harm to the reef, the four bombs, weighing a total 1.8 metric tons (4,000 pounds), were dropped into more than 50 meters (164 ft) of water away from the reef's coral structures. The bomb drop was originally planned to occur at the Townshend Island bombing range, DELL Precision M6400 CPU Fan

but after controllers reported that the area was not clear of hazards, the emergency jettison occurred. Australian senator Larissa Waters responded to the news by asking, "Have we gone completely mad? Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?" SONY Vaio VPC-EB290X CPU Fan

Human impact on coral reefs is significant. Coral reefs are dying around the world.[1] In particular, coral mining, pollution (organic and non-organic), overfishing, blast fishing and the digging of canals and access into islands and bays are serious threats to these ecosystems. HP Envy 17-1090eo CPU Fan

Coral reefs also face high dangers from pollution, diseases, destructive fishing practices and warming oceans.[2] 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, Toshiba Satellite A210-1CF CPU Fan

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.

In 2008 estimates assembled from coral reef specialists from around the world indicated that 19% of the existing area of coral reefs has been already been lost, Dell Vostro 3450 CPU Fan

and that a further 15% are likely to be lost over the subsequent 10–20 years.[3] Only 46% of the world’s reefs could be currently regarded as in good health.[3] 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, Toshiba Satellite A10-103 CPU Fan

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, all coral reefs will be in danger.

In the Caribbean Sea and tropical Pacific, direct contact between coral and 40–70% of common seaweeds cause bleaching and death of coral tissue viaallelopathic competition. Compaq Presario A900 CTO CPU Fan

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 seaweeds or their extracts. The seaweed ten expanded to occupy the dead coral's habitat.[6] However, as of 2009, only 4% of coral reefs worldwide had more than 50% algal coverage. ACER Aspire 4736ZG CPU Fan

Further, there is no recent global trend towards algal dominance.[2]

Competitive seaweed and other algae thrive in nutrient-rich waters in the absence of sufficient herbivorous predators. Herbivores include fish such asparrotfish, surgeonfish, tangs and unicornfish.

Over fishing, particularly selective over fishing, can unbalance coToshiba Satellite A10-103 CPU Fan

ral 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 waxcetyl palmitate in their tissues. SONY MCF-519PAM05 CPU Fan

Most predators find this wax indigestible.[7] 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. SONY Vaio VPC-EB290X CPU Fan

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.

Although some aquarium fish species can reproduce in aquaria (such as Pomacentridae), most (95%) are collected from coral reefs.[ HP Pavilion dv7-2043cl CPU Fan

Intense harvesting, especially in South-East 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. HP Pavilion dv7-2130ev CPU Fan

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.HP 608772-001 CPU Fan

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.[12] 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.[13] Toshiba Satellite A100-194 CPU Fan

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, HP Pavilion tx1205/ CT CPU Fan

destroying habitat for the remaining fish and other animals important for reef health.[12] 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.[12] HP Pavilion dv6640ep CPU Fan

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. COMPAQ Presario CQ42-401TU CPU Fan

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) Toshiba Satellite A300D CPU Fan

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.[12]

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. HP Pavilion dv8397ea CPU  Fan

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. HP Pavilion dv9821ea CPU Fan

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.

Reefs in close proximity to human populations are subject to poor water quality from land- and marine-based sources. HP COMPAQ TC4200 CPU Fan

In 2006 studies suggested that approximately 80 percent of ocean pollution originates from activities on land.[15] 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, SONY Vaio VGN-NW228F CPU Fan

nutrients and pesticides from agriculture, wastewater, industrial effluentand 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.[16]

An increasing fraction of the global population lives in coastal areas. HP G62-b16ST CPU Fan

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.[16]

Pollution can introduce pathogens. HP 580696-001 CPU Fan

For example, Aspergillus sydowii has been associated with a disease in sea fans, andSerratia marcescens, has been linked to the coral disease white pox.[16]

Reefs in close proximity to human populations can be faced with local stresses, including poor water quality from land-based sources of pollution.[16] HP Pavilion dv6-3049tx CPU Fan

Copper, a common industrial pollutant has been shown to interfere with the life historyand 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. HP G42-380LA CPU Fan

Dust also blows from the Gobi and Taklamakan deserts across Korea, Japan, and the Northern Pacificto the Hawaiian Islands.[18] Since 1970, dust deposits have grown due to drought periods in Africa. Dust transport to the Caribbean and Florida varies from year to year[19] with greater flux during positive phases of the North Atlantic Oscillation.[20] Toshiba Qosmio G30-167 CPU Fan

The USGS links dust events to reduced health of coral reefs across the Caribbean and Florida, primarily since the 1970s.[21] Dust from the 1883 eruption of Krakatoa in Indonesiaappeared in the annular bands of the reef-building coral Montastraea annularis from the Florida Reeftract.[22]

Sediment smothers corals and interferes with their ability to feed and reproduce. HP Pavilion dv7-1157cl CPU Fan

Pesticides can interfere with coral reproduction and growth.

Excess nutrients, 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. Compaq Presario CQ40-408AX CPU Fan

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) HP Mini 110-1110ET CPU Fan

 

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.[23] Both plants also obscure sunlight, killing both fish and coral. High nitrate levels are specifically toxic to corals, while phosphates slow down skeletal growth. HP Pavilion dv7-1157cl CPU Fan

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.

A study released in April 2013 has shown that air pollution can also stunt the growth of coral reefs; HP Pavilion dv6-3163eo CPU Fan

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, HP Pavilion dv9740us CPU Fan

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 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. HP COMPAQ NX9420 CPU Fan

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 tires!), and even entire vessels.[16]

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. HP Pavilion dv7-4150ec CPU Fan

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. HP Pavilion dv5-1102tu CPU Fan

Rising sea levels due to climate change requires coral to grow to stay close enough to the surface to continuephotosynthesis. Also, water temperature changes can induce coral bleaching as happened during the 1998 and 2004 El Niñoyears, in which sea surface temperatures rose well above normal, bleaching or killing many reefs. SONY VGN-SZ220 CPU Fan

High sea surface temperature (SST) coupled with high irradiance (light intensity), triggers the loss of zooxanthellae, a symbiotic algae, and its dinoflagellate pigmentation in corals, turning coral white. Zooxanthellae provide up to 90% of their hosts' energy supply. Healthy reefs can often recover from bleaching if water temperatures cool. HP Pavilion dv7-6011tx CPU Fan

However, recovery may not be possible ifCO
2 levels rise to 500 ppm because concentrations of carbonate ions may then be too low.[26][27]

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. HP Pavilion dv5-1040eb CPU Fan

If global temperatures increase by 2 °C during the twenty-first century, coral may not be able to adapt quickly enough.[28]

Warming seawater is also expected to cause migrations in fish populations to compensate for the change. ASUS F3Jv CPU Fan

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.[29]

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. IBM ThinkPad R50p 2887 CPU Fan

Ocean acidification results from increases in atmospheric carbon dioxide. Oceans absorb around one–third of the increase.[5]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.[5]

Ocean surface pH is estimated to have decreased from about 8.25 to 8.14 since the beginning of the industrial era,[32] and a further drop of 0.3–0.4 units is expected.[33SONY VGN-CS36GJ/R CPU Fan

] 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. Toshiba Satellite A215-S4807 CPU Fan

Corals experience reduced calcification or enhanced dissolution when exposed to elevated CO
2.[34]

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. Toshiba Satellite Pro M10-SP405 CPU Fan

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, HP Pavilion dv4-1120us CPU Fan

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".Compaq Presario C550EM CPU Fan

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. Toshiba Qosmio E15-AV101 CPU Fan

Within the last 20 years, once prolific seagrass meadows and mangrove forests, which absorb massive amounts of nutrients andsediment, have been destroyed. Both the loss of wetlands, mangrove habitats and seagrass meadows affect the water quality of inshore reefs.[39] Toshiba Satellite L645D-S4056 CPU Fan

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.[40] The rocks are ground and mixed with other materials, like cement to make concrete. Toshiba Satellite A305-S6837 CPU Fan

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. HP Pavilion dv7-4087cl CPU Fan

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. HP Pavilion dv5-1118es CPU Fan

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. Toshiba Satellite A665-S6050 CPU Fan

Buoys can attach to the seafloor using concrete blocks as weights or by penetrating the seafloor, which further reduces damage.[42]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, HP Pavilion G72-259WM CPU Fan

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. HP Pavilion dv6-3109ca  CPU  Fan

The global standard for recording threatened marine species is the IUCN Red List of Threatened Species.[44] 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. HP Pavilion dv6782eg CPU Fan

By 2008, the IUCN had assessed all 845 known reef-building corals species, marking 27% as Threatened 20% asnear threatened and 17% as data deficient.[45]

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. SONY UDQF2PH52CF0 CPU Fan

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.

The Great Barrier Reef is the world's largest coral reef system. The reef is located in the Coral Sea. A large part of the reef is protected by the Great Barrier Reef Marine Park. Toshiba UDQFRPH33CCM CPU Fan

Particular environmental pressures include runoff, salinity fluctuations, climate change, cyclic crown-of-thorns outbreaks, overfishing, and spills or improper ballast discharge.

Southeast Asian coral reefs are at risk from damaging fishing practices (such as cyanide and blast fishing), overfishing, sedimentation, pollution and bleaching. Toshiba Satellite A505-S6980 CPU Fan

Activities including education, regulation and the establishment of marine protected areas help protect these reefs.

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. HP Pavilion dv7-2025es CPU Fan

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. TOSHIBA Satellite L300 CPU Fan

According to one source, Indonesia will lose 70 percent of its coral reef by 2050 if restoration action does not occur.

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": HP G62-a10EJ CPU Fan

Tubbataha Reef, Marine Park in Palawan, Apo Island inNegros Oriental, Apo Reef in Puerto Galera, Mindoro, and Verde Island Passage off Batangas. Philippine coral reefs is Asia's second largest.

Coral reefs in Taiwan are being threatened by human population growth. Dell MF60100V1-Q000-G99 CPU Fan

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. HP Envy 15 CPU Fan,HP Pavilion dv7-1190er CPU Fan,Toshiba Satellite A105-S4074 CPU Fan

Partager cet article

Repost 0
Published by batterys
commenter cet article

commentaires