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he oceans have absorbed approximate- of the century they could be over 800 ppm. munities.”
This would result in an additional surface
T ly 525 billion tons of carbon dioxide water pH decrease of approximately 0.3 pH G lobal warming is caused by the accu-
units by 2100. mulation of carbon dioxide and other
from the atmosphere, or about one third heat-trapping gasses in the atmosphere.
of the anthropogenic carbon emissions W hen CO2 reacts with seawater, the re- These gases act as a blanket, preventing
released. This absorption has benefited duction in seawater pH also reduces the heat of the sun to escape through our
humankind by significantly reducing the the availability of carbonate ions, which atmosphere. This is primarily due to fossil
greenhouse gas levels in the atmosphere play an important role in shell formation fuel burning and deforestation and many
and minimizing some of the impacts of for a number of marine organisms such as scientists believe that this is causing sea
global warming. However, the ocean’s corals, marine plankton, and shellfish. This surface temperatures to rise. Ocean warm-
uptake of carbon dioxide is having nega- phenomenon, which is commonly called ing is extremely dangerous to coral organ-
tive impacts on the chemistry and biology “ocean acidification,” could have profound isms, which are very sensitive to changes in
of the oceans. Hydrographic surveys and impacts on some of the most fundamental temperature. Increased water temperatures,
modeling studies have revealed that the biological and geochemical processes of which may be linked to global warming,
chemical changes in seawater resulting the sea in coming decades. Some of the can cause mass coral bleaching. This oc-
from the absorption of carbon dioxide are smaller calcifying organisms are important curs when coral polyps, stressed by heat
lowering seawater pH. The pH of ocean sur- food sources for higher marine organisms. or ultraviolet radiation, expel the algae
face waters has already decreased by about Declining coral reefs due to increases in that live within them. These algae, called
0.1 units from an average of about 8.21 to temperature and decreases in carbonate zooxanthellae normally provide the coral
8.10 since the beginning of the Industrial ion would have negative impacts on tour- with up to 80% of its energy, making zoox-
Revolution. Estimates of future atmospheric ism and fisheries. Abundance of commer- anthellae essential for coral survival. The
and oceanic carbon dioxide concentrations, cially important shellfish species may also algae are also normally responsible for the
based on the Intergovernmental Panel on decline and negative impacts on finfish color of coral, so when they are expelled,
Climate Change, CO2 emission scenarios may occur. This rapidly emerging scientific the coral appears white or “bleached.” There
and coupled ocean-atmosphere models, issue and possible ecological impacts have is a chance that bleached coral can recover
suggest that by the middle of this century raised serious concerns across the scientific if conditions return to normal quickly
atmospheric carbon dioxide levels could and fisheries resource management com- enough.
reach more than 500 ppm, and near the end
