In March the divers of Atlantis Diving College will start looking for dangerous algae to know if it is present in Lebanese waters. This research project will be carried out in collaboration with the Environmental Sciences Program of the American University of Beirut. Our aim is to inform the Lebanese diving community of this toxic algal species and to report any sighting of its presence in our waters.

If you have seen this u/w plant in Lebanon please report it by clicking here.

NAME: Caulerpa taxifolia

What is it?
Caulerpa is a green algae native to tropical waters that typically grows to a small size and in limited patches. In the late 1970s this species attracted attention as a fast-growing and decorative aquarium species that became popular in the saltwater aquarium trade. An accidental mutated hybrid of this species was cultured for display at the Stuttgart Aquarium in Germany and provided to aquariums in France and Monaco.

Why are we looking for it?
Around 1984 this species was released from an aquarium in Monaco into Mediterranean waters, and rapidly spread from an initial patch of about one square yard to over two acres by 1989. Meinesz reports that by 1997 it blanketed more than 11,000 acres of the northern Mediterranean coastline and has recently been reported off northern Africa.

Genetic analysis suggests that all Caulerpa taxifolia plants in the Mediterranean are clones of the original, inadvertently released saltwater aquarium plant. In areas where the species has become well established, it has caused ecological and economic devastation by overgrowing and eliminating native seaweeds, seagrasses, reefs, and other communities.

In the Mediterranean, it is reported to have harmed tourism and pleasure boating, devastated recreational diving, and had a costly impact on commercial fishing both by altering the distribution of fish as well as creating a considerable impediment to net fisheries. The dense carpet that this species can form on the bottom could inhibit the establish-ment of juveniles of many reef species, and its establishment offshore could seriously impact commercial fisheries and navigation through quarantine restrictions to prevent the spread of this species.

In the Mediterranean, the algae is causing a “major ecological event” (Boudouresque et al., 1995). Caulerpa taxifolia invades the dominant seagrass, Posidonia oceanica, and in invaded areas is capable of killing up to 45% of Posidonia shoots in one year (Villele and Verlaque, 1994). Where it is found in the Mediterranean, other native seaweeds are being more or less totally replaced the numbers of individuals of Mollusca, Amphipoda and Polychaeta in Caulerpa taxifolia meadows is greatly reduced (Bellan-Santini et al, 1996).

Caulerpa taxifolia is toxic to herbivores such as sea urchins and fish; where the plant is the sole food source. Caulerpenyne extract inhibits or delays the proliferation of several phytoplanktons of the marine food chain (Lemee et al., 1997). Toxins of Caulerpa taxifolia prevent the mitotic spindle formation in sea urchin eggs, therefore inhibiting sea urchin reproduction. Caulerpa taxifolia has no natural predator in the Mediterranean. It creates a monoculture eliminating ecological diversity.

How it got here?
Long distance spread of Caulerpa taxifolia can be the result of cleaning anchors and fishing nets or emptying ship ballast water and aquarium contents. (Meinesz, 1992; Sent et al, 1994). Short distance spread occurs when fragments are transported via currents. Newly colonized sites are often harbors, marinas and other places where boats anchor (Boudouresque et al 1995).

How to recognize it?

Fronds are feather-like “leaf blades” each of which has a relatively wide central axis (rachis), from which grow many pinnules
Primary fronds grow directly on the stolons at regularly spaced intervals; fronds may be quite short or even absent in shallower water (leaving only the stolons), becoming longer in deeper water in low light conditions; primary fronds are 2-15 cm (1-6 in) in the tropical version of the alga, while primary fronds of the Mediterranean strain range from 5 cm in shallower water, to 40 cm at depths of 15 m, and even to 60-80 cm long (24 in to 38 in) at greater depths (Meinesz, 1995); branching fronds grow from the primary fronds

Pinnules are up to 1 cm long; number 4 to 7 per cm along each side of the frond axis; are usually upcurved, tapering at the ends; some pinnules are split in two at the ends (bifurcate); pinnule spacing and length depend on light availability (Meinesz, 1995)

I hope this informarion is enough for you to recognise it.
For further information send an email to

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