Mar Menor
Knowledge and Tools for a Future Oyster Restoration Action

Photo: Javier Giménez

The Mar Menor Oyster Initiative

This initiative is supported by 17 scientists belonging to different research institutions (Spanish Institute of Oceanography, IEO; University of Basque Country, UPV-EHU; Institute of Marine Sciences, ICM-CSIC; Dalhousie University, Halifax, Canada; Marine Research Center, CIMA-Xunta de Galicia; University of Santiago de Compostela, UsC) and led by IEO (Oceanographic Centers of  Murcia, Baleares, Málaga and Canarias).


The Mar Menor (37°48′ 52.847″ N, 0° 47′ 2.431″ W) is a hypersaline protected lagoon located in the southeast of Spain. It is one of the largest coastal lagoons in the Mediterranean region, as well as in Europe. The lagoon average depth is 3.6 m with an extension of 135.5 km2. A sandbar called La Manga, of about 23 km in length and a maximum width of 900 m, separates the lagoon and the Mediterranean Sea with three shallow main channels connecting both water bodies. Traditionally, the Mar Menor has been an oligotrophic and hypersaline (53-70 ups) ecosystem with sedimentary bottoms dominated by seagrasses but current salinity is about 42-48 ppt.

Since the 1970s, this ecosystem underwent a great oceanographic transformation which, in addition to agriculture and uncontrolled tourism development led eutrophication and a massive phytoplankton bloom in 2015, locally named thegreen soup. The bloom has been recurrent ever since causing disastrous ecological and economic consequences in the area.

Nature based Solutions are supported by nature, cost-effective, and provide environmental, social and economic benefits and help build resilience. Therefore, the Mar Menor oyster initiative aims to

  • gain KNOWLEDGE on the feeding physiology of the oyster and its nutrient extraction capability to recover eutrophic environments.
  • develop the necessary TOOLS for a future oyster restoration action within the framework of a comprehensive plan for the restoration of the lagoon.
  • promote oyster restoration as a best management practice through OUTREACH and society engagement in Mar Menor.


This initiative begins with the project RemediOS, Proof of concept for the use flat oyster in bioremediation actions: seed production with local broodstock; the Mar Menor as a case study. This project is developed with the collaboration of the Biodiversity Foundation (Spanish Ministry for Ecological Transition and the Demographic Challenge), through the Pleamar Program, co-financed by the European Maritime and Fisheries Fund (EMFF).

During the 1980s, the flat oyster (Ostrea edulis) population in Mar Menor thrived with an estimated population of 135 million. The last evaluation, carried out in 2006, reported a reduction of almost 10 times and the current status of the oyster populations in the lagoon is unknown. With the oyster disappearance, the ecosystem services they provided were also gone. Any restoration and bioremediation action requires the production of seed from native breeders with water from the lagoon. Thus the difficulties inherent in the cultivation of this species, together with the fact that it has never been tried to reproduce this population in a hatchery, leads to the proposed proof of concept with which to assess the viability of this production. Multiple collaborative activities with the fishermen, NGOs and outreach to society complete this first program of the Mar Menor initiative.

Native oyster in the water around the Barón Island, Mar Menor lagoon. (Photo: Javier Giménez)
Native oyster veliger larvae from local adult flat oysters kept under laboratory conditions at the Spanish Institute of Oceanography laboratory. (Photo: Marina Albentosa)
Native oyster seed collected in Mar Menor, October 2020. (Photo: Marina Albentosa)


Marina Albentosa
Senior Researcher
Spanish Institute of Oceanography (IEO, Murcia, Spain)