Environmental Engineering Reference
In-Depth Information
may enable corals to be more resilient. Herbivorous fishes and
invertebrates such as sea urchins play an important role in
reef health by mowing down and eating weedy algae and thus
clearing settling spots for young corals. Those herbivores may
help damaged reefs to recover. However, not all species of cor-
als respond the same way. Some species have a degree of toler-
ance to lower pH, while others experience harmful carryover
effects through developmental stages or even generations after
short-term exposure. Bleaching, acidification, and diseases are
expected to compound each other, and will reduce survival,
growth, reproduction, larval development, settlement, and
postsettlement development. Interactions with local stresses
such as pollution, sedimentation, and overfishing will likely
intensify the effects of climate change.
Ocean acidification effects are not restricted to shell pro-
duction. Mussels use stiff, stretchy structures called byssus
threads to attach onto surfaces. In lower pH, the threads break
more easily and lose elasticity; the mussel's ability to hang on
drops by about 40% in more acidic water. Effects have been
seen on behavior and development of a number of marine ani-
mals. Fish use gills to regulate pH balance, but the early larval
stages don't have gills and cannot regulate pH balance in this
way. Exposure of eggs and larvae of a common estuarine fish
to elevated CO
2
severely reduced survival and growth. The
eggs were more vulnerable to high CO
2
-induced mortality than
the larvae. Atlantic longfin squid eggs raised in seawater with
elevated CO
2
were slower to hatch than those raised in normal
seawater. Mineral structures called statoliths, which help the
squid sense movement, were smaller in acidified water; they
had more pores and were oddly-shaped. With abnormal stato-
liths, the squid might have trouble orienting and swimming.
Behavior is also altered in many animals. For example,
young clownfish (familiar as the cartoon fish, Nemo) nor-
mally stay close to the reef in which they live. But as the water
becomes more acidic they tend to wander farther and far-
ther from home. This boldness is not good for their survival
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