Global warming turning sea into acid bath
Pastor Dale Morgan
From The Times
June 9, 2008
*Global warming turning sea into acid bath*
Mark Henderson, Science Editor
Increasing carbon dioxide emissions could leave species such as coral
and sea urchins struggling to survive by the end of the century because
they are making the oceans more acidic, research led by British
scientists suggests.
The study of how acidification affects marine ecosystems has revealed a
striking impact on animal and plant life. The findings, from a team led
by Jason Hall-Spencer, of the University of Plymouth, indicate that
rising carbon emissions will alter the biodiversity of the seas
profoundly, even before the effects of global warming are taken into
account.
Greater concentrations of carbon dioxide in the atmosphere mean that
more of the gas becomes dissolved in seawater, increasing its acidity.
This will have good consequences for some species, but be catastrophic
for others.
Dr Hall-Spencer's team investigated the likely effects of acidification
by studying natural underwater vents off the coast of Italy, where
carbon dioxide bubbles up through the sea floor. This makes the water
around the vents significantly more acidic than it is in surrounding areas.
The study, published in the journal Nature, shows that certain species
are very badly affected by rising acidity. Corals of the Caryophyllia,
Cladocora and Balanophyllia varieties, for example, were common in on
the sea bed in the region, but absent close to the vents. Sea urchins
and sea snails were also affected badly by the high acidity.
Other species, including sea-grass and a type of algae known as
Sargassum, thrived as the extra carbon dioxide has a fertilising effect.
This extra growth, however, can be damaging to other sea life -
Sargassum is an alien invasive species, carried to the region in the
ballast of shipping.
The research team is the first to use natural underwater carbon dioxide
vents to assess how acidity caused by the gas influences sea life. “Our
field studies provide a window on the future of the oceans in a high CO2
world,” Dr Hall-Spencer said.
“We show the dramatic ecological consequences of ocean acidification
including the removal of corals, snails and sea urchins and the
proliferation of invasive alien algae.
“Our observations verify concerns, based on laboratory experiments and
model predictions, that marine food webs will be severely disrupted and
major ecological tipping-points are likely if human CO2 emissions
continue unabated.”
This appraisal of life in a more acidic ocean was if anything
conservative, Dr Hall-Spencer said, because it mimicked future
ecosystems only partially.
The acidity around carbon dioxide vents can be reduced by rough
conditions, which dilute the water - something that would not happen if
the whole ocean was highly acidic.
The researchers also noted that while fish continued to swim through
more acidic waters, they avoided breeding or spawning in them. “That
isn't a problem at the moment, as they can go elsewhere,” Dr
Hall-Spencer said. “But in a more acidic ocean there will be no escape.”
Global warming will also have an independent impact on sea life, by
raising ocean temperatures.