seaweed that grows in the shape of a series of connecting disks. (The
census was limited to creatures large enough to be seen with the naked
eye.) In this vent-free zone, sixty-nine species of animals and fifty-one
species of plants were counted.
When Hall-Spencer and his team set up their quadrants closer to the
vents, the tally they came up with was very different. Balanus perforatus is
a grayish barnacle that resembles a tiny volcano. It is common and
abundant from west Africa to Wales. In the pH 7.8 zone, which
corresponds to the seas of the not-too-distant future, Balanus perforatus
was gone. Mytilus galloprovincialis, a blue-black mussel native to the
Mediterranean, is so adaptable that it’s established itself in many parts of
the world as an invasive. It, too, was missing. Also absent were: Corallina
elongata and Corallina officinalis, both forms of stiff, reddish seaweed;
Pomatoceros triqueter, a kind of keel worm; three species of coral; several
species of snails; and Arca noae, a mollusk commonly known as Noah’s
Ark. All told, one-third of the species found in the vent-free zone were no-
shows in the pH 7.8 zone.
“Unfortunately, the biggest tipping point, the one at which the
ecosystem starts to crash, is mean pH 7.8, which is what we’re expecting
to happen by 2100,” Hall-Spencer tells me, in his understated British
manner. “So that is rather alarming.”
SINCE Hall-Spencer’s first paper on the vent system appeared, in 2008,
there has been an explosion of interest in acidification and its effects.
International research projects with names like BIOACID (Biological
Impacts of Ocean Acidification) and EPOCA (the European Project on
Ocean Acidification) have been funded, and hundreds, perhaps thousands,
of experiments have been undertaken. These experiments have been
conducted on board ships, in laboratories, and in enclosures known as
mesocosms, which allow conditions to be manipulated on a patch of
actual ocean.
Again and again, these experiments have confirmed the hazards posed