Alex Meinesz shows Alan Caulerpa's most versatile and damaging features.

Countless towns on the coast of the Mediterranean Sea depend on a mix of fishing and tourism. In "Green Invader," biologist Alex Meinesz takes Alan fishing off of Nice, in waters that have been fished for generations. Until now, that is. Today, when fishermen pull up their nets, they are clogged with a green weed. And there are few fish.

The weed - actually a tropical alga called Caulerpa taxifolia - isn't native to the area, and with no natural predators, it's taking over the Mediterranean. So far it covers 1,000 miles of coastline.

Caulerpa was first spotted in 1984, most likely released unwittingly by the nearby Monaco Oceanographic Museum where Jacques Cousteau was once director. Caulerpa not only ruins fishing, it also kills other plants by blocking out sunlight, starving the animals that rely on them for food. At this rate, Caulerpa may turn the Mediterranean into a biological desert.

 

If deemed safe, this Floridian slug may help halt the algae's advance.

Most recently, the weed has been spotted in San Diego, where environmental consultant Rachel Woodfield is leading the effort to destroy it. Luckily, the Caulerpa patches are still small enough that complete eradication should be possible.

But in the Mediterranean, the problem requires far more drastic measures. Meinesz hopes to import a special slug, one of Caulerpa's natural predators from the Caribbean. Can this slug save the Mediterranean- without wreaking havoc of its own?

For more on this topic, see the web feature:
Nature vs. Nature
Algae Alert