A scientific study warns that sea warming and ocean acidification could seriously compromise mussel production in the Mediterranean by 2050, with “almost total” summer mortality in future scenarios, which could translate into lower supply and higher prices, and oysters, although more resilient, are also not immune to losses and slower growth.
The research was conducted by a team associated with CNRS, Ifremer and Sorbonne Université, and sought to understand “who” and “what”: the impact of climate change on the survival and productivity of two key species in Mediterranean aquaculture, the Mediterranean mussel (Mytilus galloprovincialis) and the Pacific oyster (Magellan gigas).
The “when” and “where” are at the heart of the alert: the experiment took place for 14 months, between 2022 and 2023, with unfiltered water from the Thau Lagoon, in the south of France, and the results were published in an article in the science magazine in December this year.
The “why” is straightforward: oysters and mussels are relevant to the coastal economy and the food supply, and the study suggests that the Mediterranean could become too hostile an environment, especially in summer, to maintain production levels similar to current ones, especially in the case of mussels.
What did the study simulate
To reach their conclusions, the researchers simulated climate conditions from 2050, 2075 and 2100, heating the water between +1 °C and +3 °C and enriching it with CO₂ to reproduce acidification, while maintaining an “ecologically realistic” environment (with natural fluctuations and the presence of phytoplankton, microorganisms and other factors typical of the lagoon).
The logic of the “how” was to avoid short and overly controlled tests: by using unfiltered water and conditions closer to the field, the study tried to get closer to what aquaculture faces on a daily basis, including thermal stress, variations in oxygen and biological pressure.
The most worrying data comes from mussels: even under current conditions, the study reports high summer mortality and, when applying the 2050 scenario, it describes that summer mortality becomes “almost total”, pointing to the risk of productive collapse if there is no adaptation.
And the oysters? More resistant, but not immune
In the case of oysters, the scenario is less dramatic than in mussels, but still penalizing: survival remains relatively high in the closest scenarios, but drops in more extreme simulations and, above all, growth slows down markedly in future conditions.
The study describes, for example, a reduction in survival and a slowdown in growth in end-of-century scenarios, as well as effects on reproductive maturity and the initial development of offspring, which can affect productivity and increase unpredictability for producers.
In practice, this can mean longer production cycles to reach commercial size, greater exposure to risks (such as harmful algal blooms, pollution and pathogens) and increased costs — factors that ultimately reach the consumer in the form of reduced availability and higher prices.
What could change on consumers’ plates
When it is said that “we will not be able to eat” mussels and oysters from the Mediterranean, the most plausible scenario is not an absolute disappearance, but rather disruptions in local production: frequent shortages in the summer, greater dependence on other sources, changes in consumption seasons and greater price volatility.
There are also signs of fragility already observed in past episodes: Thau Lagoon, for example, has a history of extreme events that affected production, and the eastern Mediterranean records episodes of mass mortality on farms, which gives context to the study’s warning.
As for solutions, the authors themselves and news that cite the work point out adaptation paths: selection of more resistant varieties, co-cultivation with algae (“multitrophic” approaches) and gradual transfer of some activities to the open sea, where the water tends to be less extreme in temperature and acidity.
In the end, the study is read as a warning to act early: “We are very close to a breaking point,” said Fabrice Pernet, quoted in statements to AFP, arguing that adaptation will have to accelerate to avoid structural losses in Mediterranean aquaculture.
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