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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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