Study tracks global warming threats to tropical shellfish

Some of the best oysters in the world come from Apalachicola Bay.
Shellfish face multiple threats linked to global warming.

Commercial mussel hatcheries in India seen as threatened by climate change

Staff Report

FRISCO — Ocean acidification isn’t the only threat to the planet’s shellfish. In parts of the tropics, warming ocean temperatures and increased rainfall is likely to dilute salt concentrations on the surface of the sea, which will change microscopic communities of bacteria and plankton.

That, in turn, will affect other species higher on the food chain, especially as future conditions may favor disease-causing bacteria and plankton species which produce toxins, such as the lethal paralytic shellfish toxin. These can accumulate in shellfish such as mussels and oysters, putting human consumers at risk.

Scientists recently explored how those changes could affect the fledgling green mussel industry in South-West India. Working on the Mangalore coast, the scientists raised mussels under high temperature/low salt conditions whilst simultaneously exposing them to toxic plankton and bacteria species.

“If the changes in the environment put the mussels’ bodies under higher stress levels than usual, and we then challenge them with these microorganisms, the immune system may become compromised,” said  Dr, Lucy Turner, explaining the findings reported by the Society for Experimental Biology.

The results showed that the combination of both a warmer temperature and reduced salinity had a significant effect on the health of the mussels.

Turner said the changes could threaten the rapidly-growing tropical shellfish industry, already under pressure from India’s increasingly urbanised population.

“We know that climate change is causing a change in the timing and duration of the monsoon which can significantly lower the seawater salinity … this is likely to increase the chance of outbreaks of toxic plankton blooms and make farming bivalves such as mussels increasingly challenging,” Turner said.

The findings point to the need for more extensive monitoring.

“The Indian government needs to be vigilant about monitoring coastal water quality, particularly as the shellfish industry continues to grow,” Turner said.

The researchers now plan to determine whether similar results are observed for oysters and clams, whilst a related project is investigating how climate change may affect prawn farms.

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