CLIMATE CHANGE AND OCEAN ACIDIFICATION - Marine Pollution: What Everyone Needs to Know - page 179

less and have weaker shells, making them more vulnerable
to predators. Sea urchins also seem resistant to OA, largely
because they have genes that provide resistance and can evolve
rapidly. Researchers raised larvae in water with either low or
high CO 2 , sampled the larvae, and used DNA-sequencing tools
to determine which parts of the genetic makeup changed. By
looking at the function of each gene that changed, researchers
were able to identify which particular genes were critical for
sea urchin survival under acidic conditions.
Ocean acidification can degrade entire ecosystems, result-
ing in homogenized communities dominated by fewer plants
and animals. In the waters by Castello Aragonese, an island off
the coast of Italy, volcanic vents naturally release CO 2 , creat-
ing different levels of acidity, which provide a glimpse of what
the future communities could look like. Three zones—low,
high, and extremely high acidity—representing conditions
of the present day, 2100, and 2500 respectively were selected
for sampling. Researchers removed animals and vegetation
from rocks and examined the rocks periodically for recovery.
In more acidic water the number and variety of species was
reduced. In both high and extremely high acidic plots, fleshy
algae increased and took over, because sea urchins and other
grazers were either not present or did not graze on the algae,
while they did so in the lower acidity zone. Calcareous grazers
are important in maintaining the balance in marine ecosys-
tems and are among the most vulnerable species to OA.
How can organisms protect themselves against effects of
warming and acidification?
Many studies consist of placing marine animals in labora-
tory tanks with low pH water for a few days or months to
see how they respond. Fish and shellfish larvae often fail to
thrive and don't grow as big or live as long as those in more
alkaline waters. But some species show substantial resilience.
Unlike most laboratories, organisms in the real ocean live in a