Project duration: October 2024 – October 2025
Status: Completed
Grantee: University of Oxford
Co-funded by: The Rauch Foundation  

THE CHALLENGE:

Poros island hosts extensive Posidonia oceanica meadows, one of the Mediterranean’s most important marine ecosystems, which support biodiversity, act as blue carbon sinks, and protect coastlines from erosion.

Within the national framework for aquaculture planning, Poros was identified for a potential 28-fold increase in fish farming, affecting up to 25% of the island’s coastline. This scale of expansion posed a serious threat to local marine ecosystems. Fish farms discharge excess feed and fish waste into surrounding waters, which can degrade seagrass meadows by reducing light penetration, altering sediment chemistry, and creating anoxic conditions.

Despite growing concern among scientists and local communities, there is a lack of robust, site-specific data on the scale and mechanisms of fishfarms’ impact on these sensitive ecosystems. This evidence gap limits the ability of local actors to advocate effectively for marine protection or for more sustainable aquaculture practices in the Argosaronic and beyond.

THE SOLUTION:

To address this critical gap, the AEF invited the University of Oxford to design and implement a dedicated research project focused on Poros.

The project combined non-invasive underwater field surveys with historical satellite analysis to generate robust, site-specific evidence on the scale and mechanisms of Posidonia seagrass degradation linked to fish farming.

By collaborating with local partners, the research ensured that the scientific evidence is directly applicable to local conditions, thereby informing conservation and aquaculture policy and strengthening the position of local advocates. The study also included comparative analysis of a site where aquaculture had been removed, offering valuable insights into the potential for Posidonia meadow recovery.

By generating essential baseline data, this work strengthens efforts to protect seagrass meadows and associated marine life, while supporting informed decision-making for the future of coastal ecosystems in Greece.

THE OUTCOMES:

Field Expedition

– 3-week field expedition on Poros, collecting the most comprehensive site-specific data on aquaculture impacts on Posidonia oceanica to date.

– Data gathered from 3 active fish farms, 1 historic (decommissioned) site, and multiple control sites across 5+ locations.

– 3,000+ photo quadrats and visual observations analysed to compare seagrass health near fish farms and unaffected areas.

Initial Findings

– Seagrass degradation was detected up to 900 metres from fish farms with Posidonia coverage reduced by ~53% and leaf length by up to 46% within 450m.

– Little to no recovery observed 14 years after fish farm removal, highlighting Posidonia’s extremely slow regeneration rate.

Scientific Impact

– Findings are being prepared for peer-reviewed publication (expected 2026) and will inform marine protection, spatial planning, and local advocacy.

Policy Impact

– Preliminary findings were presented to the Hellenic Parliament in June 2025, during a session of the Subcommittee on Water Resources on Marine Spatial Planning and Sustainable Aquaculture, providing robust, evidence-based input to the policy debate.

The unanimous recommendation by the Central Council for Urban Planning to reject the proposed industrial aquaculture zone in Poros, 17th August 2026, marked a significant milestone, highlighting the power of robust scientific evidence and coordinated local action in shaping marine spatial planning decisions.

OUR PARTNER ORGANIZATION: 

The University of Oxford, through its highly regarded Department of Zoology, has led extensive research on seagrass ecosystems, including Posidonia meadows, combining marine ecology with advanced satellite analysis to assess human impacts on marine habitats. Its long-standing scientific work in the Mediterranean provides authoritative insights that strengthen the project’s evidence-based approach and support effective conservation action.

READ ALSO: 

Posidonia Oceanica: Our Valuable Underwater Forests

Thalassa Mana Concert: A Harmonious Blend of Art and Environmental Awareness

Mapping the Posidonia oceanica Seagrasses of Poros and Methana

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