Escaped aquarium alga strangles sea life

An alga commonly sold as an aquarium plant has escaped into the Mediterranean where it is wreaking havoc with local wildlife.

An alga commonly sold as an aquarium plant has escaped into the Mediterranean where it is wreaking havoc with local wildlife.

Scientists have discovered that the same strain of alga has turned up off the coast of California, probably after sticking to the underside of boats travelling from its Mediterranean stronghold.

The fern-like seaweed, Caulerpa taxifolia, normally inhabits very warm tropical waters, but the period spent in captivity has enabled it to adapt to the relatively cooler waters of the Mediterranean and California, the scientists say.

Jan Pawlowski, head of the laboratory that did the study at Geneva University, said: "It's a natural alga but it has been living in the environment of a marine aquarium for some time." The alga grows up to 8cm a day and quickly expands over the seabed, strangling other wildlife. It also gives off a toxin that can kill smaller marine organisms. DNA tests on samples from the Mediterranean and California showed the alga was identical to that sold in Europe for aquariums.

"Our results show that the Californian alga is the same as the invasive Mediterranean strain, calling for its rapid eradication to prevent a new invasion," the scientists report in the journal Nature. The alga is though to have first escaped about six years ago and has since spread to cover more than 6,000 hectares of sea in the north-west of the Mediterranean. The strain grows more rapidly than its native form and can clone itself without sexual reproduction.

Dr Pawlowski said the alga may originally have come from Australia, possibly by sticking to the anchors of boats travelling from one area to another.