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I. Introduction
A. Definition: Coral reefs as defined by Fagerstron (1987), are carbonate structures produced
and maintained by an assemblage of calcifying organisms, predominately scleractinian corals
but also including coralline algae. (Barber, 1255-1271)
B. Symbiosis
1. Coral animals
2. Photogenic algae
3. To fuel calcification, high-light levels are needed without UV radiation (Barber, 1255-1271)
4. Plankton and algae are a foundation of the oceanÕs food web (Crib, 18-21)
5. The coral reef assemblage requires temperatures in the general range of 20-30 C, but
optimal growth occurs in the extremely narrow range of 25-29 C. Corals thrive in high
salinity waters, moderate wave action and continuous currents. ( Barber, 1255-1271)
C. Evolution of Corals (Crib, 18-21)
1. Charlie Veron, former chief scientist at the Australian Institute of Marine Science, there
has been five mass extinctions which either wiped out or partly eliminated the corals.
a. Volcanoes, rotting organisms, and Bacterial activity
b. In every case it took 10 million years or longer for the ocean equilibrium to recover and
for corals to appear again in the fossil record. (Crib, 18-21)
D. What do corals do for the world? (Dupree, 22-30)
1. Coral reefs, which cover less than 1 percent of the ocean floor, are the principal
habitat for 25 percent of the ocean's species.
2. Both people and wildlife benefit from the protection they provide against storm surges and
tsunamis.
3. Globally, coral reefs are estimated to contribute more than $30 billion a year in direct
net benefits to human economies.
II. Rise in Carbon Emissions
A. Pre-Industrial Coral Reefs
B. As atmospheric levels of CO2 continue to build, the amount absorbed by the oceans also
increasing resulting in lower pH levels (Rahmstorf, 12-13)
1. PH levels
a. 27 billion tons of carbon dioxide are released each year by human activity
b. In the past 200 years the oceans have absorbed approximately half of the CO2 produced by
fossil fuel burning and cement production.
c. The uptake of CO2 has led to a reduction of the pH of surface seawater of 0.1 units,
equivalent to a 30 per cent increase in the concentration of hydrogen ions.
d. If global emissions of CO2 from human activities continue to rise on current trends, then
the average pH of the oceans could fall by 0.5 units by the year 2100. (Crib, 18-21)
III. Calcification
A. Corals and plankton rely on sea water saturated with carbonates and bicarbonates to form
their skeletons. (Crib, 18-21)
B. However, as more CO2 dissolves out of the atmosphere and acidity intensifies, the carbonate
saturation declines, making it much harder for these animals Š and indeed all shellfish Š
to calcify, or form their shells and skeletons (Crib, 18-21)
C. Acceptable levels of CO2 for calcification (Crib, 18-21)
1. When CO2 levels in the atmosphere reach about 500 parts per million (ppm), you put
calcification out of business in the oceans
2. The worldÕs atmospheric CO2 levels are presently about 385 ppm
3. They have risen by pm since 1960. Even with our current efforts to cut greenhouse
emissions, they are expected to reach 500 ppm by mid-century.
a. unbridled growth in China, India
b. expansion in fossil fuel use everywhere
D. In laboratory and mesocosm studies, a decrease of 0.2 to 0.3 units in seawater pH inhibits
or slows calcification in many marine organisms, including corals. (Zeebe, 51-57)
1. average surface ocean pH has already decreased by ~0.1
2. Reduced calcification in shellfish such as oysters and mussels would impact worldwide
commercial aquaculture production
IV. Temperature (Dupree, 22-30)
A. Over the past century, ocean temperatures have increased an average of 1 degree F, with
frequent and prolonged higher temperature spikes in many tropical regions. Warmer oceans
have triggered widespread episodes of coral "bleaching," a condition linked to
environmental stress.
1. Bleaching: rid themselves of the microscopic algae that live inside them and give coral
polyps their distinctive colors
B. Most corals require shallow water that is clear and largely free of sediment and nutrients.
They need warm tropical waters to thrive, but not too warm: The majority of coral species
exist at the upper end of their maximum temperature range.
C. If high temperatures persist, the corals will die.
1. 1998 was a global wake-up call: the most devastating year for corals since record-keeping
began. In a year that already was unusually warm, an El Ni–o weather pattern cranked up the
heat still further in Pacific waters near the equator.
2. The 1998 water temperatures triggered a rare mass bleaching that left few reefs unscathed.
An estimated 16 percent of the world's corals died in a single year, and local casualty
rates were far higher.
a. Among Indian Ocean reefs, losses of up to 75 percent were common.
b. In the Seychelles Islands, more than 90 percent of the corals died.
V. Pollution, Overfishing, and Human activity
A. Oil spills: A new study shows that the chemicals typically used to clean up oil spills harm
corals even more than the oil does (Branan, 8-9)
B. Destructive fishing patterns, tourism, even snorkeling (Walsh, 42-43)
1. Commercial-fishing boats sailing over corals can damage or destroy reefs that have taken
centuries to build.
2. overfishing disrupts the delicate ecological balance that allows corals to thrive
3. Hunting fish for hobbyists
C. Fertilizer run-off (Walsh, 42-43)
1. A stream of nitrates and phosphates exists which is flowing into the Gulf of Mexico
a. can create vast algae blooms that suck all the oxygen out of surrounding waters.
b. Some fish can ŅoutrunÓ this
c. Can choke corals to death because they are stationary
d. a recent study in Australia found that heavy rains can transport pollutants as far as 80
miles (130 km) away from the shoreline.
VI. Why is this a problem?
A. Coral reefs drive ocean productivity and are the base of the food web which supports krill,
whales, tuna and our fisheries (Crib, 18-21)
B. They play a vital role in removing carbon dioxide from our atmosphere (Crib, 18-21)
C. The seasÕ ability to soak up excess CO2 from the air may decline (Crib, 18-21)
1. This in turn will lead to a further rise in atmospheric carbon levels which, scientists
fear could turn into a runaway greenhouse effect
2. Marine plankton at risk from acid oceans are also among the major producers of the EarthÕs
breathable oxygen
a. Other algae and plant life may simply take over the role of producing oxygen
D. Eastern Dry Rocks Reef (Dupree, 22-30)
1. Research and Studies
2. Virtually all of the reef's majestic elkhorn corals vanished in less than six years, along
with purple semi fans, fingerlike pillar corals, and many of the fish and other creatures
that lived among them.
3. "A few years ago, we'd look for diseased corals out here, and we'd report any that we
found," says Peter Wassylenko, a Key West dive instructor, "Now, if you find a living,
healthy coral, you get excited."
E. Declining rates
1. A comprehensive assessment by the National Oceanic and Atmospheric Administration, released
July 7, found that half the coral reefs in U.S. territory are in fair or poor condition, a
significant drop since the last survey, in 2005.
2. Another study, published recently in Science, found that almost one-third of coral
species--the tiny polyps that build the underwater reefs--are threatened with extinction,
up from less than 2% a decade ago.
F. Tourism
1. "Coral reefs are beautiful, but they are also tremendous economic resources," says NOAA
marine biologist Jenny Waddell. (Vergano, 2008)
VII. Steps to be Taken
A. The only known way to reverse this is the slow weathering and dissolution of limestone
mountain ranges and carbonaceous rocks into the sea, a process that takes millions of years
(Crib, 18-21)
B. Examine the exceptions to general patterns rather than the norms (Knowlton, 54)
1. The uninhabited atolls of the Central Pacific are a case in point and cause for cautious
optimism
a. Despite increased warming and coral bleaching throughout the Pacific, these reefs still
support extraordinarily abundant fish populations dominated by apex predators and among the
highest reported abundances of living coral and coralline algae.
b. Have they escaped massive bleaching, or simply recovered?
2. Hope is that thet have recovered due to high recruitment and rapid growth of corals, and
lower levels of macroalgal overgrowth, coral disease, and outbreaks of coral predators.
VIII. Future Predictions and Conclusion
A. Kent Carpenter, head of the Global Marine Species Assessment- "The corals will be the
canary in the coal mine in terms of the effect climate change will have on our ocean,"
(Walsh, 42-43)
B. KnowltonÕs hope of recovery and adaptation.
Works Cited
Barber, Richard T., and Anna K. Hilting. "THE CHANGING HEALTH OR CORAL REEFS." Human and Ecological Risk Assessment 7 (2001): 1255-271.
Branan, Nicole. "CHEMICALS WORSE FOR CORALS THAN OIL." Geotimes 52 (2007): 8-9.
Crib, Julian. "ACID OCEANS." Ecos Apr. 2008: 18-21.
Dupree, Joe. "CORAL CRISIS." National Wildlife 45 (2007): 22-30.
Knowlton, Nancy, and Jeremy B.C. Jackson. "SHIFTIN BASELINES, LOCAL IMAPCTS, AND GLOBAL CHANGE ON CORAL REEFS." PLoS Biology Feb. 2008: Pe54.
Rahmstorf, Stefan. "ACID LEVELS INCREASE IN OCEANS." Pollution Engineering 39 (2007): 12-13.
Vergano, Dan. "'INVASIVE HUMANS THREATEN U.S. CORAL REEFS." USA Today [McLean, Virginia] 7 July 2008.
Walsh, Bryan, and David Bjerklie. "CORAL UNDER SIEGE." TIME 4 Aug. 2008: 42-43.
Zeebe, Richard E., and James C. Zachos. "CARBON EMISSIONS AND ACIDIFICATION." Science 321 (2008): 51-57.
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