Acidified Landscape Foretells Grim Future for Coral Reefs

Underwater vents allow scientists to assess the acidic effect of carbon dioxide on ocean life

Huge vents covering the sea-floor - among the strangest and most
spectacular sights in nature - pour carbon dioxide and other gases into
the deep waters of the oceans.

week, as researchers reported that they had now discovered more than
50,000 underwater volcanic springs, they also revealed a new use for
them - as laboratories for measuring the impact of ocean acidification
on marine life.

seas are slowly being made more acidic by the increasing amounts of
carbon dioxide from factories and cars being pumped into the atmosphere
and then dissolved in the sea. The likely impact of this acidification
worries scientists, because they have found that predicting the exact
course of future damage is a tricky process.

That is where the
undersea vents come in, says Dr Jason Hall-Spencer of the University of
Plymouth. "Seawater around these vents becomes much more acidic than
normal seawater because of the carbon dioxide that is being bubbled
into it," he told a meeting of the American Association for the
Advancement of Science in San Diego, California, last week. "Indeed, it
reaches a level that we believe will be matched by the acidity of
oceans in three or four decades. That is why they are so important."

part of his research, Hall-Spencer has scuba-dived into waters around
vents and used submersibles to study those in deeper waters. In both
cases the impact was dramatic, he told the conference.

"The sea
floor is often very colourful. There are corals, pink algae and sea
urchins. But I have found that these are wiped out when the water
becomes more acidic and are replaced by sea grasses and foreign,
invasive algae.

"There is a complete ecological flip. The seabed
loses all its richness and variety. And that is what is likely to
happen in the next few decades across the world's oceans."

Hall-Spencer also noted that in acidic seawater a type of algae known as coralline algae - which act as the glue holding coral reefs together - are destroyed.

coralline algae are destroyed, coral reefs fall apart," he said. "So we
can see that coral islands like the Maldives face a particularly
worrying future. Rising sea levels threaten to drown them, while
acidic waters will cause them to disintegrate.

"It is a very worrying combination."

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