References
參考資料
[1] Ocean Acidification: The Other Carbon Dioxide Problem. PMEL Carbon
Program, National Oceanic and Atmospheric Administration. Retrieved from
[2] Staff Reporter. Sea Urchins Adapting to Increased Oceanic Acidifcation
(
/
.
h
[3] Welch, C. Sea Change – Can Sea Life Adapt? (2013) The Seattle Times.
Since
the dawn of the i ndust r ial
revolution, human activities have caused a surge
in the amount of carbon dioxide (CO
2
) released
into the atmosphere. Each year, the ocean
absorbs approximately 25% of atmospheric CO
2
.
As atmospheric CO
2
levels increase, the ocean’s
CO
2
concentration follows suit. This dissolution
alternate carbonate chemistry in surface water
leads to a drop in its surface pH. The phenomenon
is known as ocean acidification [1].
Ocean acidification has led to a drop in the
pH of surface ocean waters by about 0.1 pH units
since the 1950s. While this number appears to be
insignificant, recall that the pH scale is logarithmic.
The minute change belies a 30% increase in
acidity [1]. Fluctuations in the ocean’s CO
2
levels
are a direct threat to the growth and development
of marine life. Marine critters rely on the calcium
carbonate in seawater to build their exoskeletons,
but carbonate ions become less available with
increased acidity. As a result, scientists are studying
how well organisms such as molluscs, crustaceans,
and corals are able to adapt to the increasingly
acidic conditions.
Marine biologist, Gretchen Hofmann, and her
group have been observing the adaptability of
sea urchins to increasing ocean acidification.
Sea urchins exhibit spherical-shaped bodies,
covered in needle-like protrusions, and are found
ubiquitously in the world’s oceans. Considered as
a keystone species, any changes in the population
size of sea urchins would directly influence other
marine organisms [2].
The size of sea urchin larvae is critical to its
ability to swim and the amount of food it can
obtain. In her prel iminar y studies, Hofmann
exposed sea urchin larvae to water containing
high CO
2
levels and compared their sizes to sea
urchins grown in less acidic conditions. While
most lar vae were unable to reach thei r ful l
potential sizes, some of them seemed surprisingly
unaffected by the acidity. This prompted her and
her colle
Kelly, to investigate whether sea urchins that hail
from a coastal area naturally exposed to higher
water acidity, had any evolutionary advantage
over other sea urchins in coping with acidification.
Their results showed that organisms in Northern
California, a region with higher ocean acidity due
to coastal upwelling, displayed a different genetic
profile from their relatives in other coastal regions.
The profile showed robust genetic variance for
larvae sizes, suggesting that sea urchins may have
hope in adapting to future conditions, particularly
when reared from urchins from different regions.
In other words, mating the hardy northern male
sea urchins with the southern females revealed
