Following the increase of coastal urbanization, 46% of the Posidonia oceanica meadows have disappeared or become threatened by a number of factors including boat anchoring. In the Aegean islands, where recreational yachting is a major touristic activity this environmental threat is an increasing problem. This can be backtracked to boat owners who are probably not aware of the key role of seagrass meadows or of the damage they may cause.

Posidonia oceanica

Archipelagos Institute of Marine Conservation (AIMC) has developed a new ecological mooring method for sailing boats and yachts, that prevents damages to seagrass meadows. As this is being currently tested, there was the need to also assess the extent of existing damages in seagrass meadows. For this purpose a new research protocol was developed for the assessment of anchor damaged on Posidonia seagrass meadows and this was tested in one bay in Lipsi Island, where the new moorings will also be experimentally installed.

This new method will allow us to compare the current status of the seagrass meadows with the results of future monitoring, after the installation of the new mooring method. The aim of this project is to evaluate the benefits of this method and to improve the resilience of seagrass in the Aegean Sea. So far, transects were drawn in one bay of Lipsi and seagrass and anchor damages were monitored every 5m using a quadrat. The depth of the meadows and the presence of invasive species and changes in the habitat were also measured.

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P. oceanica meadows were mainly concentrated on the outskirts of the bay whereas in the middle part, seagrass was distributed more in patches. To avoid the risk of damage by rocky coasts, the majority of boats prefer to anchor in the middle of a bay. The investigated meadows showed crushes as well as large scars originating from boat anchoring. As P. oceanica is a slow growing plant its recovery takes a long time. If boats continue to anchor in the two main meadows in this bay, there is a risk of significant decrease in their size followed by a reduction of seagrass coverage.

Ongoing work includes the training of team members in the methodology to continue this study in different bay areas of Lipsi Island such as the bay in the West of Kambos and Katsadia, in the South of the island, while at a later stage the study area will also be extended to other parts of the northern Dodecanese islands.

Léa Brieau, University of Southern Brittany, France