Seagrass meadows and their potential degradation due to the expansion of aquaculture in the Argolic Gulf

Recent findings highlight that the absence of seagrass habitats from the Environmental Impact Assessment for the Organized Aquaculture Development Areas (POAY) heightens concerns about the environmental impacts of existing and planned aquaculture activities in the region.

This study was conducted at the request of local stakeholders seeking to better understand the condition of marine ecosystems in their area, at a time of increasing plans for aquaculture expansion. The initiative was supported by the Argosaronic Environment Foundation and the Rauch Foundation, in collaboration with Katheti, with iSea carrying out the scientific work.

In this context, and building on earlier surveys initiated in 2022, the study focused on mapping Posidonia seagrass meadows and other marine vegetation in key areas of the Argolic Gulf, helping to fill in a significant knowledge gap in the region.

As part of the 2025 study, iSea mapped 18.29 hectares of Posidonia oceanica and Cymodocea nodosa meadows and assessed their historical presence near existing or planned aquaculture development zones, through a combination of field research and analysis of multiple data sources, such as available satellite imagery dating back up to 50 years.

Taking into account historical data, a degradation and even disappearance of seagrass meadows is indicated, due to long-term intensive aquaculture activities. A characteristic example is the enclosed Vourlias Bay, where the substrate now consists exclusively of mud and sand, in areas where the presence of seagrass meadows was historically recorded prior to aquaculture.

One of the key and most concerning findings of the study is the significant overlap of seagrass meadows with the planned POAYs in the area. Specifically, according to scientific recommendations, fish farms should maintain a minimum distance of 800 meters from the boundaries of Posidonia meadows, while the impacts of aquaculture on them can extend up to 3 km from the cages. On the other hand, the impacts of such installations on Cymodocea nodosa have not been sufficiently studied, yet.

Despite these recommended distances, at Cape Thyni almost the entire Posidonia meadow (13.28 hectares) lies within the 3 km impact zone of fish farms, while installations are located even as close as 300 meters from this meadow. At the same time, in the area from Cape Bournias to Cape Fokiano, cages are planned at distances of as little as 100 meters from a Posidonia patch. Additionally, the Cymodocea nodosa seagrass meadow mapped adjacent to the Vourlia Bay is almost entirely located within a distance of less than 800 meters from aquaculture facilities.

Although the particular areas of interest do not fall under any formal protection designation, the intense development pressure in the Argolic Gulf and the scale of the proposed increase in production and expansion of aquaculture, combined with the existing habitat degradation, make their protection imperative. Given the ecological importance of seagrass meadows and the critical ecosystem services they provide, scientific knowledge should serve as a guide for improved planning aimed at preventing their further degradation.

The knowledge gained highlights the inadequate planning of aquaculture expansion in the area and strengthens the claims of the local community for more effective management of the region’s valuable ecosystems. New installations and the expansion of existing ones should be implemented based on the minimum recommended distances from seagrass meadows, while environmental impact assessments should incorporate these habitats and include enhanced environmental monitoring and management measures.

The findings underline that without improved planning and protection, further loss of these habitats is likely, with consequences for marine life, fisheries, and coastal communities.

In collaboration with the local community, we invite you to attend the presentation of the findings and join the open discussion on Friday, 24th, 17.30-20.30, at the building of the Management Body of the Protected Areas of the Southern Peloponnese, at Astros.

Find the full report here.

Learn more about the project “Reposidonia in the Argosaronic Gulf” here.

For more information, contact Kyriaki Pyloridou, Project manager, iSea, kyriaki.pyloridou@isea.com.gr