Date Published: 21/10/2025
Mar Menor's first oyster reef takes shape to help clean the lagoon
Native oysters could help clean the lagoon’s waters as scientists warn of dangerously low oxygen levels

The Mar Menor’s first oyster reef has been launched in a bid to help clean the polluted lagoon, just as scientists warn it is once again in a critical state following Storm Alice.
Researchers from the Spanish Institute of Oceanography (IEO-CSIC) and the environmental group ANSE have begun open-sea trials to test how native flat oysters can filter pollutants and improve water quality. Around 55,000 young oysters bred at the Murcia Oceanographic Centre have been placed on a reef near Isla del Barón, where they could retain up to 100 tonnes of nitrogen a year, about a fifth of the nutrients that reach the lagoon annually.
“The goal is to study how oyster farming can naturally reduce pollution in the lagoon,” explained project coordinator Marina Albentosa.
Oysters work as a natural ecological cleaning system, and it is estimated that the oysters in the Mar Menor could filter all the water in just 23 days, offering hope for a natural solution to the lagoon’s long-standing nutrient overload.

But the lagoon’s condition remains fragile. According to IEO researcher Juan Manuel Ruiz, oxygen levels have plummeted since the storm, particularly in the southern area.
“At the bottom, we are already recording oxygen levels typical of anoxia, below 2 milligrams per litre. Right now they are at 1.5,” he warned, adding that such low readings have previously led to fish and crustacean deaths. The sharp drop is caused by layers of fresh rainwater preventing oxygen from circulating to deeper parts of the lagoon.
While the oyster project offers hope for long-term recovery, experts say urgent action is still needed to prevent another environmental crisis in the Mar Menor.
Images: IEO
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