REPOSIDONIA IN THE ARGOSARONIC GULF

The Argosaronic Gulf is an area known for its natural beauty and, due to its location and its close distance to Attica, it is considered one of the most popular destinations. However, intense tourist activity poses threats to the marine ecosystem and to Posidonia, including pollution (wastewater, litter) and mechanical damage caused by uncontrolled anchoring.

Within the framework of the Reposidonia program, iSea has begun operating in the area with the aim of mapping the priority habitat Posidonia oceanica and identifying the emerging threats it faces.

What we have achieved so far:

In 2022 iSea mapped for the first time the Posidonia meadows around Spetses, Spetsopoula and Velopoula through satellite imagery and data collected through field surveys. In 2023, the mapping of the meadows was extended to the island of Hydra.

The fact that vehicle circulation is prohibited on the islands, combined with the fact that many transfers to and from them are carried out by sea taxis, leads to increased boat traffic around the islands. However, the available port facilities are insufficient to serve such a number of vessels, resulting in the region’s increased tourism contributing significantly to the degradation of the Posidonia meadows mapped around these two islands, due to the uncontrolled anchoring of boats on the seagrass.

Despite the fact that the area of meadows in Spetses is quite large, they are affected by fragmentation and degradation in multiple locations. The situation is similar in the strait between Spetses and Spetsopoula. Finally, in Spetsopoula, although no corresponding anthropogenic pressures were observed, necrosis was observed in many parts of the meadow, leaving the rhizomes of the Posidonia uncovered, which now harbour various species of seasonal vegetation.

In Hydra the distribution of meadows is quite limited and where Posidonia is present it is not coherent. On the beaches of Agios Nikolaos and Agios Georgios (Bisti) this may be the result of uncontrolled anchoring, as the areas are almost exclusively accessible from the sea and there is intense boat activity. In addition, at Molos beach, the pier attracts higher activity of boats anchored in the bay.
The degradation of the Posidonia meadows in Spetses and the limited distribution of these in Hydra further intensify the need to protect and restore the remaining meadows in these areas!

In 2024, iSea focused on mapping the Posidonia meadows in the area of Poros Island and the Methana Peninsula, which receive hundreds of visitors daily, especially during the summer months. Among the impacts identified, the presence of aquaculture units represents an additional threat to the meadows due to excessive nutrient overflow and sedimentation. As part of the project activities, the historical presence of seagrass meadows was also investigated in relation to both current and past aquaculture facilities (active and abandoned).

In the two study areas, the distribution of Posidonia meadows is scarce and incosistent along the western coasts. The meadows appear denser and more continuous in the area north of Methana and the southernmost part of Poros. This distribution may be partly attributed to the bathymetric characteristics of the two regions, which are mainly defined by steep, rocky underwater reefs. Scarcity and patchiness of the meadows are more pronounced in areas associated with aquaculture operations, while in certain tourist bays of Poros, these patterns may be linked to anchoring pressure.

Actions and targets for 2025

The following actions will be carried out in the context of this year's project:

iSea continues the mapping of Posidonia meadows and other marine phanerogams found in the Argolic Gulf, with the aim of better understanding their distribution in relation to areas with existing or aquaculture development plans. At the same time, the historical presence of Posidonia near these facilities is being investigated.

The collection of scientific data aims to create a reference baseline for the future management and conservation of the area. In addition, through awareness raising and communication activities, iSea seeks to inform and engage the wider public on the value of this important habitat and the need to preserve it, in collaboration with the local community.

Find the project's reports below: