Seagrass, Posidonia oceanica, on its way to extinction

By March 29, 2013 Ocean News

Meet the Posidonia oceanica, also called seagrass. It is an endemic flowering underwater plant of the Mediterranean sea. It forms one of the most important habitats in this sea, called Posidonia meadows. One of these habitats, between Ibiza and Formentera islands, is considered as a World Heritage site by the UNESCO. And, since the 80’s is at risk and on the IUCN Red List. It’s on the red list because one of the most absurd things ever. An aquarist created a hybrid in his home aquarium between two different caulerpas (a tropical green algae) and, when he was cleaning his aquarium, he threw the water into the sea. So his hybrid, which was more resilient than a normal caulerpa, started to grow and invade all the Posidonia habitats.


Invasive Caulerpa taxifolia is the main threat for the Posidonia, but not the only one. A Poseidonia oceanica plant is fixed to the substrate by rhizomes, which could be uprooted by anchors and destroy the habitats. Also, it is very sensitive to pollution (it’s used as a indicator for clean waters), and sensitive to the water temperature. The species is not at risk, according to Javier Romero, an ecologist from University of Barcelona, but that’s just for now.


In order to protect the meadows, the ecologists are taking local actions. For example, near the Medes Islands (Catalonia), a protected area, they added some buoys for the boats to stay away from the sensitive habitats. The vessels are not allowed to use their anchors, so if there’s no place available, they have to go away. It’s a simple system, but it’s working, so they are trying to convince other communities to do the same. It won’t be difficult to convince them, as they are aware of the seagrass meadows. Even some fishermen try to protect them, because they know that the healthier and bigger the meadow is, the more big fish are present.

If you would like to take action and want to fight the Caulerpa here is how you can help. Call the authorized professionals if you spot Caulerpa in the Mediterranean. DO NOT pull it up, as you can spread it! A frag of this algae can live almost a week without water, and if throw it to the sea again, it will continue growing! So the only way to fight the Caulerpa is to watch the contaminated areas and try not to spread it more. And if you dive or fish near them, clean everything you used!

Since the Caulerpa invaded due to the release in the Ocean by an aquarist: How do you think we can make more aquarists aware of what releasing species in to the Ocean can do to the environment?

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  • […] The plan is controversial, to say the least. On one hand, the project is relatively eco-friendly, utilizing the site of a former quarry, which will need less construction compared to a cruise terminal built from scratch. On the other hand, building a cruise terminal on Gozo Island would not only disrupt the slow, local lifestyle of the island, but also wreak havoc on the seabed, which houses a variety of sea life and some of Europe’s largest underwater meadows of poseidonia algae. […]

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