the Industrial Revolution, ocean acidity has risen by 30 percent
as a direct result of fossil-fuel burning and deforestation.
And within the last 50 years, human industry has caused the
world’s oceans to experience a sharp increase in acidity
that rivals levels seen when ancient carbon cycles triggered
mass extinctions, which took out more than 90 percent of the
oceans’ species and more than 75 percent of terrestrial
ocean acidity is now considered to be just as much of a formidable
threat to the health of Earth’s environment as the atmospheric
climate changes brought on by pumping out greenhouse gases.
Scientists are now trying to understand what that means for
the future survival of marine and terrestrial organisms.
June, ScienceNOW reported that out of the 35 billion
metric tons of carbon dioxide released annually through fossil
fuel use, one-third of those emissions diffuse into the surface
layer of the ocean. The effects those emissions will have on
the biosphere is sobering, as rising ocean acidity will completely
upset the balance of marine life in the world’s oceans
and will subsequently affect humans and animals who benefit
from the oceans’ food resources.
damage to marine life is due in large part to the fact that
higher acidity dissolves naturally-occurring calcium carbonate
that many marine species–including plankton, sea urchins,
shellfish and coral–use to construct their shells and
external skeletons. Studies conducted off Arctic regions have
shown that the combination of melting sea ice, atmospheric carbon
dioxide and subsequently hotter, CO2-saturated surface waters
has led to the undersaturation of calcium carbonate in ocean
waters. The reduction in the amount of calcium carbonate in
the ocean spells out disaster for the organisms that rely on
those nutrients to build their protective shells and body structures.
link between ocean acidity and calcium carbonate is a directly
inverse relationship, which allows scientists to use the oceans’
calcium carbonate saturation levels to measure just how acidic
the waters are. In a study by the University of Hawaii at Manoa
published earlier this year, researchers calculated that the
level of calcium carbonate saturation in the world’s oceans
has fallen faster in the last 200 years than has been seen in
the last 21,000 years–signaling an extraordinary rise
in ocean acidity to levels higher than would ever occur naturally.
authors of the study continued on to say that currently only
50 percent of the world’s ocean waters are saturated with
enough calcium carbonate to support coral reef growth and maintenance,
but by 2100, that proportion is expected to drop to a mere five
percent, putting most of the world’s beautiful and diverse
coral reef habitats in danger.
the face of so much mounting and discouraging evidence that
the oceans are on a trajectory toward irreparable marine life
damage, a new study offers hope that certain species may be
able to adapt quick enough to keep pace with the changing make-up
of Earth’s waters.
a study published last week in the journal Nature Climate
Change, researchers from the ARC Center of Excellence for
Coral Reef Studies found that baby clownfish (Amphiprion melanopus)
are able to cope with increased acidity if their parents also
lived in higher acidic water, a remarkable finding after a study
conducted last year on another clownfish species (Amphiprion
percula) suggested acidic waters reduced the fish’s sense
of smell, making it likely for the fish to mistakenly swim toward
the new study will require further research to determine whether
or not the adaptive abilities of the clownfish are also present
in more environmentally-sensitive marine species.
the news that at least some baby fish may be able to adapt to
changes provides optimism, there is still much to learn about
the process. It is unclear through what mechanism clownfish
are able to pass along this trait to their offspring so quickly,
evolutionarily speaking. Organisms capable of generation-to-generation
adaptations could have an advantage in the coming decades, as
anthropogenic emissions push Earth to non-natural extremes and
place new stresses on the biosphere.