Forgot Password?
Home arrow GreeniacsArticles arrow Water arrow Coral Bleaching
Written by Suzanne Heibel   
Share |
Sunday, 22 February 2009

Coral Bleaching

It is what some scientists have called a biological “murder mystery.”1 Miles of coral reefs all over the world are losing their colors and dying off under the sea, leaving nothing but a vacant skeleton of what was once a habitat of bustling life. The cause is unknown. Some say it’s the rise in water temperatures. Others point to change in ocean salinity. The why is unclassified, but global climate change has been named the culprit by many.

The Basics of Coral

Coral is an animal. It's often mistaken for a plant because it is immobile and well, looks like a leafless tree. Coral reefs are started by one single polyp that attaches itself to a rock on the sea floor, asexually reproduces to create thousands of clones, which create more corals that grow, grab onto other polyps, and eventually form a reef.2 And as demonstrated by say, the Great Barrier Reef, these things can get down right gigantic. Sure they cover only one percent of the ocean floor but they support a hefty quarter of all marine species.

Another misconception about coral is that they are, all on their own, comprised of fabulous bright colors. Coral is actually the color white naturally, their symbiotic algal counterpart is in fact what gives them those beautiful yellow or pink hues.3 But algae species are not just for a colorful wrapping, they use photosynthesis to convert sunlight into carbohydrates that the corals use as their source of food.4 As you may know, coral lives in tropical waters. What you may not know is that these warmers water are nutrient poor so everything that comes out of a creature then goes into another as food. So to fulfill this mutual relationship, the coral's excrements become food for the algae.5

Coral are Sensitive Creatures

Coral bleaching began occurring in the 1980s and the array of possibilities of why extends from the grip of sensitivities coral has to its surroundings. Coral has adapted to the sea that surrounds it, so any slight change precipitates stress on the polyp. Changes in ocean salinity, temperature, solar radiation, tidal patterns, and nutrient levels all can stress out coral enough that it will actually dislodge its algal partner in search of a new species of algae that can adapt quicker to whatever change is causing the habitat disruption. However, if no better adjusted species binds to the polyps, within a few weeks to months the coral will remain bleached and die.6

The Suspects

First, warmer water changes oxygen levels because colder water can hold more oxygen than warmer waters. So even a slight change in temperature may cause coral to feel a bit choked up and stressed out. Warmer water can also be caused by increased solar radiation (more UV rays passing through the degrading atmosphere) and since algae are the photosynthesizers it affects them instead of the coral. When there is a lot of sunlight, the algae photosynthesize it too quickly, which can cause “oxygen toxicity,” which is excess oxygen inhalation that can cause tissue damage to the coral. The coral will then expel the algae because they are creating a toxic environment, but then the symbiotic relationship is lost and the coral eventually dies.7 Another factor is that the increased sunlight can disrupt the enzyme system (the system within an organism that uses proteins to increase the speed of chemical reactions within the body) of the algae and inhibit the amount of oxygen that the coral receives.8 Once again, the coral are not satisfied.

Despite the plethora of alarming evidence pointing to warming waters, scientists are not positive that they are at all or at least completely to blame. A decrease in salinity due to extensive rain water or too much runoff will also alter the chemistry of the sea enough to cause some stress. As a side note, when water warms it also expands, and this in turn causes a decrease in salinity.9 Nonetheless, nutrient change also needs to be taken into account.

In the end, most experts would point to warming waters due to global climate change as the cause, including National Oceanic and Atmospheric Administration, who keeps precise tabs on coral bleaching through a “thermal stress outlook.”10 Those same experts also say that over-fishing, pollution, and costal development are also major contributors to the death of coral.11

Are Coral Reefs Doomed?

Just because the corals let go of their first algal relationship doesn't mean they are doomed and will not find another. It is possible for corals that have released their algae to adopt a new species and survive making a full recovery. But as humans, we need to do our part to ensure that our actions do not lead to the destruction of other species.

Browse all Greeniacs Articles Browse all Greeniacs Guides        Browse all Greeniacs Articles
_______________________________________________________________________________

1 http://www.newsobserver.com/102/story/1347425.html.
2 http://animals.nationalgeographic.com/animals/invertebrates/coral.html.
3 http://www.marinebiology.org/coralbleaching.htm.
4 http://news.mongabay.com/2007/0831-coral.html.
5 http://www.onr.navy.mil/focus/ocean/habitats/coral1.htm.
6http://www.marinebiology.org/coralbleaching.htm.
7 http://books.google.com/books?id=e5D8uPYkybcC&pg=PA33&lpg=PA33&dq=coral+oxygen+toxicity
&source=web&ots=-7FuZV0CpM&sig=7mEJW1t4N1bcJPNrGv0nUXRto7w&hl=en&sa=X&oi=book_
result&resnum=1&ct=result#PPA35,M1.
8 http://www.marinebiology.org/coralbleaching.htm.
9 Id.
10 http://coralreefwatch.noaa.gov/satellite/bleachingoutlook/outlook_messages/
bleachingoutlook_current.html.
11 http://www.nasa.gov/centers/goddard/news/topstory/2006/coral_health.html.




Add your comment
RSS comments

Only registered users can write comments.
Please login or register.

Click here to Register.  Click here to login.
Last Updated ( Monday, 07 February 2011 )

SEARCH GREENIACS.COM

Green Facts

  • Washing your clothes in cold or warm instead of hot water saves 500 pounds of carbon dioxide a year, and drying your clothes on a clothesline six months out of the year would save another 700 pounds.

  • You’ll save two pounds of carbon for every 20 glass bottles that you recycle.

  • Americans throw away more than 120 million cell phones each year, which contribute 60,000 tons of waste to landfills annually.

  • Less than 1% of electricity in the United States is generated from solar power.

  • A laptop consumes five times less electricity than a desktop computer.

  • Nudge your thermostat up two degrees in the summer and down two degrees in the winter to prevent 2,000 pounds of carbon dioxide from entering the atmosphere.

  • You will save 100 pounds of carbon for each incandescent bulb that you replace with a compact fluorescent bulb (CFL), over the life of the bulb.

  • For every 38,000 bills consumers pay online instead of by mail, 5,058 pounds of greenhouse gases are avoided and two tons of trees are preserved.

  • The World Health Organization estimates that 2 million people die prematurely worldwide every year due to air pollution.

  • States with bottle deposit laws have 35-40% less litter by volume.

  • Glass can be recycled over and over again without ever wearing down.

  • Plastic bags and other plastic garbage thrown into the ocean kill as many as 1,000,000 sea creatures every year.

  • Current sea ice levels are at least 47% lower than they were in 1979.

  • Due to tiger poaching, habitat destruction, and other human-tiger conflicts, tigers now number around 3,200—a decrease in population by about 70% from 100 years ago.

  • 82 percent of greenhouse gas emissions in the U.S. come from burning fossil fuels.

  • Recycling for one year at Stanford University saved the equivalent of 33,913 trees and the need for 636 tons of iron ore, coal, and limestone.

  • A single quart of motor oil, if disposed of improperly, can contaminate up to 2,000,000 gallons of fresh water.

  • Every week about 20 species of plants and animals become extinct.

  • Recycling 1 million laptop computers can save the amount of energy used by 3,657 homes in the U.S. over the course of a year.

  • 77% of people who commute to work by car drive alone.

  • Shaving 10 miles off of your weekly driving pattern can eliminate about 500 pounds of carbon dioxide emissions a year.

  • Turning off the tap when brushing your teeth can save as much as 10 gallons a day per person.

  • In the United States, automobiles produce over 20 percent of total carbon emissions. Walk or bike and you'll save one pound of carbon for every mile you travel.

  • A tree that provides a home with shade from the sun can reduce the energy required to run the air conditioner and save an additional 200 to 2,000 pounds of carbon over its lifetime.

  • It takes 6,000,000 trees to make 1 year's worth of tissues for the world.

  • Refrigerators built in 1975 used 4 times more energy than current models.

  • One recycled aluminum can will save enough energy to run a 100-watt bulb for 20 hours, a computer for 3 hours, or a TV for 2 hours.

  • Bamboo absorbs 35% more carbon dioxide than equivalent stands of trees.

  • Recycling aluminum saves 95% of the energy used to make the material from scratch.

  • In California homes, about 10% of energy usage is related to TVs, DVRs, cable and satellite boxes, and DVD players.

  • A steel mill using recycled scrap reduces related water pollution, air pollution, and mining wastes by about 70%.

  • Americans use 100 million tin and steel cans every day.

  • An aluminum can that is thrown away instead of recycled will still be a can 500 years from now!

  • You will save 300 pounds of carbon dioxide for every 10,000 miles you drive if you always keep your car’s tires fully inflated.

  • Americans throw away enough aluminum to rebuild our entire commercial fleet of airplanes every 3 months

  • If every U.S. household turned the thermostat down by 10 degrees for seven hours each night during the cold months, and seven hours each weekday, it would prevent nearly gas emissions.

  • Rainforests are being cut down at the rate of 100 acres per minute.

  • American workers spend an average of 47 hours per year commuting through rush hour traffic. This adds up to 23 billion gallons of gas wasted in traffic each year.

  • Recycling 100 million cell phones can save enough energy to power 18,500 homes in the U.S. for a year.