Environmental Engineering Reference
In-Depth Information
community with many different species and a complex web of
interactions. Some species are competitors for space and food;
others are potential prey or predators. Limited laboratory
studies also cannot tell you the long-term effects or if a species
can adapt to acidification. Our present understanding relies
mostly on results from short-term studies. Longer studies may
reveal that some species can adapt over time. Animals can be
impaired when abruptly exposed to elevated CO
2
, but individ-
uals that are gradually acclimated to high CO
2
may be able to
adjust over the long term. For example, coral in high CO
2
for
one week reduced calcification by about 25% in a pH decrease
of 0.1 units. In contrast, the coral could acclimate to this pH
over six months, and have even a slightly greater calcification
rate. This shows acclimation of a coral to ocean acidification.
Some mollusks have also been able to increase their tolerance
to low pH through acclimation. In one study, elevated CO
2
caused oyster larvae to reduce growth, slow their development,
and reduce survival. But when adult oysters were exposed to
elevated CO
2
while their gonads were ripening, the larvae
they later produced were larger and developed faster in the
high CO
2
conditions. Also, selectively bred larvae were more
resistant to elevated CO
2
than wild larvae. Thus, some marine
organisms may be able to acclimate or adapt to elevated CO
2
.
Another approach is studying wild populations that have
already adapted to acidic waters, which occur naturally in
some parts of the world. For example, along North America's
West Coast, the waters off Oregon have low pH due to upwell-
ing. While this does severe harm to oysters as described
above, sea urchin larvae there tolerate acidic water better than
ones from California. This suggests that these sea urchins
have the resilience and genetic variation sufficient to tolerate
ocean acidification. Researchers have found indications that
some corals have genes that provide increased resilience to
acidification.
Some corals can adapt to higher temperatures and resist
bleaching. For example, corals in the Persian Gulf withstand
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