Posidonia Habitat Mapping: Spetses & Velopoula
THE CHALLENGE
Posidonia oceanica meadows, often described as the “forests of the sea”, are among the Mediterranean’s most valuable ecosystems. They store blue carbon, stabilise coastlines and provide nursery grounds for hundreds of marine species.
In the Argosaronic, these meadows are under increasing cumulative pressure from intense anchoring, dense boat traffic, tourism-related coastal development, and uncoordinated aquaculture spatial planning. Despite their ecological and economic importance, the true extent and condition of Posidonia meadows around Spetses and the neighbouring island of Velopoula had never been systematically mapped.
Without accurate spatial data, anchoring management, marine zoning, protection considerations and conservation planning remain severely constrained.
THE PROJECT
With AEF’s support, iSea launched the first detailed site-specific mapping effort of Posidonia oceanica meadows around Spetses and the uninhabited island of Velopoula.
The project combined advanced remote sensing with intensive field validation:
- High-resolution satellite imagery was used to identify potential seagrass habitats.
- Divers, drones and remotely operated vehicles (ROVs) conducted in-situ surveys to verify and calibrate the satellite data.
- Scientific modelling techniques (Maximum Likelihood and Random Forest algorithms) were applied to produce high-accuracy distribution maps to depths exceeding 30 meters.
This integrated approach ensured robust, evidence-based outputs capable of informing marine spatial planning, anchoring management and future conservation interventions.
OUTCOMES
The project was completed according to plan, successfully delivering detailed Posidonia maps for both Spetses and Velopoula.
Impact at a Glance
- 4.1 km² of Posidonia meadows mapped providing the first comprehensive spatial assessment in the area
- Velopoula meadows documented as 11 times larger than previously recorded in Natura 2000 datasets
- 90% mapping accuracy achieved
- Creation of a reliable baseline for anchoring regulation and zoning discussions
- Strengthened scientific understanding of the area’s blue carbon capacity and biodiversity value
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