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Éva Moisan arrived at the Reserve in February and had six months to study the Halophilia stipulacea, an invasive species introduced through boat anchors that is slowly taking up more and more space on the seagrass beds. The evening before her departure, this professional Masters student from the University of Corte delivered her final report and gave nuanced answers about the consequences of the arrival of these algae in the waters of Saint-Martin. Firstly, this plant is smaller in Saint-Martin than it is in the rest of the Caribbean. Here, its rhizomes grow from 0,26 to 2,16cm per day, whereas a daily growth of up to 6cm was recorded on other Caribbean islands. Her study showed that the algae has a stunted growth on the sites where it is competing with Syringodium and Thalassia, both local species, but that it is rapidly spreading across deeper sand plains that are uninhabited by vegetation. As a measure of precaution, the first observations are pointing towards classifying this plant as a potentially invasive species – taking into account that it continues to spread, it is not regressing on any of the sites where it is already colonized, and after a year, it has appeared on five new sites. It has already been given the status of an invasive species by other islands in the Caribbean. On the other hand, the progress made during this study doesn’t permit an affirmation that this species is necessarily destructive. New studies should be able to clarify conclusions, particularly those concerning Halophilia stipulacea’s interaction with local flora. Note: the plant takes advantage by establishing itself where the native seagrass is most fragile, usually as a result of certain sites having had waste water poured into them, or being victim to destruction by way of boat anchors and their chains.
In order to avoid the destruction of seagrass beds, boats now have to use the mooring buoys that the Nature Reserve has installed at Créole Rock, Pinel and Tintamarre.
