CLIMATE CHANGE AND OCEAN ACIDIFICATION - Marine Pollution: What Everyone Needs to Know - page 176

water out from coastal regions, deeper water with high acid-
ity (called corrosive water) can upwell, and harm shellfish.
Periodic upwelling of CO 2 -rich water has already happened on
the US West Coast, where larval oyster survival has been very
low for several years because of these events. A few decades
ago, such upwelling events weren't as acidic and probably
wouldn't have been cause for concern. Hatcheries are having
trouble producing and rearing larval oysters. There has been a
reduced natural set of juvenile oysters in some estuaries where
the commercial shellfish industry relies on natural reproduc-
tion of oysters. This is due largely to the upwelling of acidic
deeper water. Workers at Oregon's Whiskey Creek Shellfish
Hatchery suspected that low pH water was killing their oys-
ter larvae. Working with Oregon State University and NOAA,
they were able to show that that was the case, and now they
monitor the pH of the ocean and time their water intakes to
ensure that oysters are exposed to less acidic water. A small
investment in pH-monitoring equipment saved the industry
millions of dollars.
In addition to the stress of warmer water, corals are very
sensitive to acidification and construct weaker shells. To add
insult to injury, when seawater is both acidic and warm (as will
be the case), corals become even more fragile due to microbor-
ers such as algae, blue-green algae, and fungi that bore tiny
holes in the coral, further weakening the skeleton. Corals will
not only have less material to build their reefs, but older parts
will erode faster due to both acidity and boring. If current
trends continue, there will be major decreases in global coral
reefs with declines in associated fishes and invertebrates.
Increasing CO 2 may be an additional stress driving a shift
from corals to seaweeds on reefs. In an experiment, coral deaths
from contact with a reef seaweed increased two- to threefold
between background CO 2 levels and a level of CO 2 projected
for late twenty-first century. Thus, coral reefs may become
more susceptible to overgrowth by seaweeds and be replaced
by them. Other members of the reef community, however,