Tiny killer threatens giant clam, aquatic emblem of the Med
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French marine biologist Nardo Vicente, of the Paul Ricard Institute of Oceanography, has monitored a field of noble pen shells off the coast of Corsica since the early nineties.
Nestled on the seabed between 26 and 40 metres underwater, the clams are around 30 years old and have grown to around 80 cm.
"In 2017 the field was in perfect health," he said.
"This year, everything was dead, absolutely a hundred percent!"
Tiny assassin
The parasite, found in the digestive systems of several of the dead noble pen shells, is from the haplosporidium genus, blamed in the United States for the mass die-off of oysters in Delaware Bay in the 1950s.
It is not yet clear what brought the tiny killer to the Mediterranean or how it is spreading so fast, although it could have arrived on the hulls of merchant ships.
But the disease appears to thrive in warming waters.
Vicente said global warming was acting to stimulate "a bunch of germs, viruses and parasites" that had lain dormant but "act fully with the rise in temperature".
The waters around the Corsican field he monitored were 20 degrees C even at 40 metres, when normally they would be 13 or 14 degrees C.
"It's completely abnormal," he said.
https://phys.org/news/2019-01-tiny-killer-threatens-giant-clam.html