Ocean Acidification

Had a good time at the MLA meeting in Rockland. The most interesting session was about Ocean Acidification. When CO2 gets absorbed into the ocean, carbonic acid is formed and the pH drops, making the oceans more acidic. Crustaceans (animals with shells) are very sensitive to acidity: the calcium carbonate in their shells dissolves.

The speaker went on about corals (not many in Maine), oysters (only a few in Maine), and urchins. He showed pictures of the larvae dissolving in water with elevated CO2 levels. Urchins are the most sensitive to dissolved CO2.

Lobsters and crabs react differently when exposed to slightly acidic water. Preliminary studies indicate that they tend to grow thicker, bigger shells with less meat inside. He cautioned the audience about the diet of the lobsters in the future, since they eat a lot of the crustacean larvae.

The urchins were over-harvested 15 years ago, but I always wondered why they never came back. And then it hit me - the other shellfish are gone, too! I remember 30 years ago, the pilings and ledges were covered with barnacles and mussels. Urchins and whelk (conch) often filled traps. Today they are pretty scarce.

What are your experiences? Aren't there now a lot, lot less barnacles, conch, mussels and urchins? Does anyone have a feel on clams, limpets or periwinkles?

What I find really scary is that we haven't had any significant changes in population, fishing, technology, pollution or other outside effects. We are far away from mainland problems. Except for the urchins, none of these species were ever commercially harvested on Criehaven or Matinicus.