Page 619 - The British Big Four

he oceans have absorbed approximately could be over 800 ppm. This would result in lobal warming is caused by the accu-
mulation of carbon dioxide and other
T G525 billion tons of carbon dioxide from an additional surface water pH decrease of
the atmosphere, or about one third of the approximately 0.3 pH units by 2100. heat-trapping gasses in the atmosphere.

anthropogenic carbon emissions released. W hen CO2 reacts with seawater, the re- These gases act as a blanket, preventing
This absorption has benefited humankind duction in seawater pH also reduces the heat of the sun to escape through our
by significantly reducing the greenhouse atmosphere. This is primarily due to fossil

gas levels in the atmosphere and minimiz- the availability of carbonate ions, which fuel burning and deforestation and many

ing some of the impacts of global warm- play an important role in shell formation for scientists believe that this is causing sea

ing. However, the ocean’s uptake of carbon a number of marine organisms such as cor- surface temperatures to rise. Ocean warm-

dioxide is having negative impacts on the als, marine plankton, and shellfish. This phe- ing is extremely dangerous to coral organ-

chemistry and biology of the oceans. Hy- nomenon, which is commonly called “ocean isms, which are very sensitive to changes in

drographic surveys and modeling studies acidification,” could have profound impacts temperature. Increased water temperatures,

have revealed that the chemical changes in on some of the most fundamental biologi- which may be linked to global warming,

seawater resulting from the absorption of cal and geochemical processes of the sea in can cause mass coral bleaching. This occurs

carbon dioxide are lowering seawater pH. coming decades. Some of the smaller calci- when coral polyps, stressed by heat or ul-

The pH of ocean surface waters has already fying organisms are important food sources traviolet radiation, expel the algae that live

decreased by about 0.1 units from an aver- for higher marine organisms. Declining within them. These algae, called zooxanthel-

age of about 8.21 to 8.10 since the begin- coral reefs due to increases in temperature lae normally provide the coral with up to

ning of the Industrial Revolution. Estimates and decreases in carbonate ion would have 80% of its energy, making zooxanthellae es-

of future atmospheric and oceanic carbon negative impacts on tourism and fisheries. sential for coral survival. The algae are also

dioxide concentrations, based on the In- Abundance of commercially important shell- normally responsible for the color of coral,

tergovernmental Panel on Climate Change, fish species may also decline and negative so when they are expelled, the coral appears

CO2 emission scenarios and coupled ocean- impacts on finfish may occur. This rapidly white or “bleached.” There is a chance that

atmosphere models, suggest that by the emerging scientific issue and possible eco- bleached coral can recover if conditions re-

middle of this century atmospheric carbon logical impacts have raised serious concerns turn to normal quickly enough.

dioxide levels could reach more than 500 across the scientific and fisheries resource

ppm, and near the end of the century they management communities.”