Page 351 - Hawaii: Diving, Surfing, Pearl Harbor, Volcanoes and More

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