SOUTH PORTLAND, Maine — They’re called dead muds. Rising levels of carbon dioxide in the atmosphere combined with unregulated nitrogen pollution are having a deadly effect on Maine’s shellfish, some researchers say.
Scientists are starting to measure the impact of increasingly acidic waters on coastal organisms, and what they’ve found is alarming. Formerly fertile shellfish flats are becoming uninhabitable wastelands of dreck. The phenomenon is another threat to Maine’s shellfish industry, estimated to be worth $60 million annually.
“They call them dead muds,” said Mark Green, an oyster grower and marine science professor at St. Joseph’s College in Standish. “The darker muds and sulfur-rich muds don’t have any clams, and those are the flats that have lower pH levels. Places where historically there have been great harvests that supported clammers for decades, you now see water quality changes that are reflected in the mud.” The more acidic the water, the lower the pH.
In these places, researchers aren’t finding dead or unhealthy shellfish. They’re finding nothing at all. It is a complete eradication.
“If you put a larval shellfish in a mud flat that has a pH level of 6.8 or 6.9, you won’t find it 24 hours later — it’ll totally dissolve,” Green said. “It’s well documented now that we see pH levels that are causing larval shellfish to die, and in relatively large numbers. And the pH projections in the future are
what’s been seen in laboratories to cause massive die-offs.”
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