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In 1989 marine biologist Alexandre Meinesz went diving off southern France and
was stunned by what he saw: a dense blanket of waving green fronds stretching
around him in every direction on the seabed. At first Meinesz had no idea what
it was. Then he made the alarming discovery that a tropical alga had taken root
in the cold water of the Mediterranean, wiping out native sea life wherever it
grew. "Deep Sea Invasion" follows Meinesz on his scientific detective hunt to
discover the source of this deadly organism, his uphill battle to alert
authorities to its danger, and the struggle to find a non-toxic way to control
it.
The invasive seaweed has since spread to harbors and coral reefs throughout the
Mediterranean and even to Australia and southern California. Given its robust
constitution and apparent lack of predators—so far only chlorine has slowed
its growth—scientists are worried that it could devastate marine ecosystems
around the world.
Meinesz, a professor of biology at France's University of Nice-Sophia Antipolis
on the Mediterranean coast, identified the alga as a strain of Caulerpa
taxifolia, a green alga native to the tropics. But this strain seems
otherworldly compared with its tropical cousins. Not only does it thrive at a
water temperature that should kill it, but it also produces a powerful toxin
that makes it deadly to fish and invertebrates (though not to humans).
Caulerpa is almost impossible to eradicate, although an infestation in a
lagoon in southern California seems to have been dealt a deathblow with a
massive dose of chlorine, which killed not only the Caulerpa but
everything else as well. In the search for a less drastic defense, Meinesz and
other scientists have identified a tropical slug that is unique in producing an
enzyme that allows it to eat Caulerpa and neutralize the toxin. Mindful
that the slug may be yet another Frankenstein's monster, just like
Caulerpa, scientists are pondering whether or not to set it loose.
Wherever Caulerpa grows it carpets the seabed in brilliant green
foliage, like a golf course. And it flourishes virtually everywhere, spreading
not by sexual reproduction but by a form of cloning known as vegetative
reproduction. A single cell of the plant—snared on an anchor or in a fishing
net—is all that's needed to introduce it to a new habitat.
Meinesz traced the secret of Caulerpa's success to the Wilhelmina Zoo in
Stuttgart, Germany. In 1980, the zoo's aquarium staff chanced on this
strain while searching for seaweed that could survive in the artificial
conditions of aquariums. The strain was either a rare mutant that just happened
to be collected in the wild or else a monster engendered at the aquarium itself—born of the harsh chemicals and bright lights bathing the fish tanks.
Hardy and decorative, Caulerpa seemed a blessing at first, and it soon
became the most popular aquarium plant on Earth. The Monaco Oceanographic
Museum obtained a sample, and it was in the harbor just beneath this
institution—where famed oceanographer Jacques Cousteau was the director at
the time—that Caulerpa was first spotted getting a toehold in nature.
The killer algae have been spreading ever since.
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