The Sixth Extinction: An Unnatural History

At the time, marine biologists were just beginning to recognize the
hazards posed by acidification. Some disturbing calculations had been
done and some preliminary experiments performed on animals raised in
labs. It occurred to Hall-Spencer that the vents could be used for a new
and more ambitious sort of study. This one would involve not just a few
species reared in tanks, but dozens of species living and breeding in their
natural (or, if you prefer, naturally unnatural) environment.
At Castello Aragonese, the vents produce a pH gradient. On the
eastern edge of the island, the waters are more or less unaffected. This
zone might be thought of as the Mediterranean of the present. As you
move closer to the vents, the acidity of the water increases and the pH
declines. A map of life along this pH gradient, Hall-Spencer reasoned,
would represent a map of what lies ahead for the world’s oceans. It would
be like having access to an underwater time machine.
It took Hall-Spencer two years to get back to Ischia. He did not yet
have funding for his project, and so he had trouble getting anyone to take
him seriously. Unable to afford a hotel room, he camped out on a ledge in
the cliffs. To collect samples, he used discarded plastic water bottles. “It
was a bit Robinson Crusoe-ish,” he tells me.
Eventually, he convinced enough people, including Buia, that he was
onto something. Their first task was producing a detailed survey of pH
levels around the island. Then they organized a census of what was living
in each of the different pH zones. This involved placing metal frames
along the shore and registering every mussel, barnacle, and limpet
clinging to the rocks. It also involved spending hours at a stretch sitting
underwater, counting passing fish.
In the waters far from the vents Hall-Spencer and his colleagues found
a fairly typical assemblage of Mediterranean species. These included:
Agelas oroides, a sponge that looks a bit like foam insulation; Sarpa salpa, a
commonly consumed fish that, on occasion, causes hallucinations; and
Arbacia lixula, a sea urchin with a lilac tinge. Also living in the area was
Amphiroa rigida, a spiky, pinkish seaweed, and Halimeda tuna, a green