Friday, December 05, 2008

Caulerpa Marine Algae

Caulerpa seaweed occurs naturally in tropical waters worldwide. Prized for their beauty and ability to uptake excess nutrients, many species of Caulerpa are now widely used in saltwater aquarium systems. In the 1980’s, a cold-tolerant and fast-growing strain of the species, Caulerpa taxifolia,was cultivated in Germany and was eventually distributed to aquarists worldwide.

This cold-tolerant strain was inadvertently introduced into the Mediterranean Sea in wastewater from the Oceanographic Museum at Monaco. The species was first reported in the Mediterranean in 1984. At that time, the algae covered a square yard and it continued to spread rapidly after it was discovered. Even small fragments can start new colonies, and soon other patches began to appear. Caulerpa has now spread over more than 13,000 hectares (32,500 acres) of seabed, and the liklihood of eradication is highly questionable.

This fast-growing "Killer algae" forms dense carpet of algae that covers the bottom in a monoculture, preventing the establishment of native seaweeds and ultimately excluding almost all marine life. Even sea urchins have no interest in eating it. It will colonize any substrate and has been found from the shoreline to depths of up to 250 feet.

In June of 2000, the highly invasive Mediterranean strain of Caulerpa taxifolia was discovered in California's Agua Hedionda Lagoon in Carlsbad, and again 75 miles north in Huntington Harbor. Genetic studies determined that these two infestations were the same strain of C. taxifolia as that in the Mediterranean Sea. The discoveries marked the first known occurrence of this strain within the Western Hemisphere, and are believed to pose a major threat to coastal ecosystems and recreational and commercial activities dependent upon coastal resources. The infested areas are covered with tarp and treated with herbicide. After a multi-million dollar eradication effort, monitoring is still needed for several years to insure no re-growth. Vigilence is also needed to insure any future infestations are identified and eradicated rapidly.

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