Seafood for Thought: How Might Climate Change Affect American Lobsters?

American lobster (Homarus americanus). Credit: NOAA

As I've experienced, this is is a typical tourist scene at many a wooden picnic table in Maine: Hungry, bibbed diners smashing blood-orange shells with mallets, prying the cracks apart to reveal sweet, coral-y flesh that's dunked in melted butter and slurped down in seconds. LOBSTAH! 

Maine’s mascot could well be the American lobster; the state hauls in more than half of the annual U.S. catch. But the crustaceans' geographic range actually extends from the shallows of Newfoundland, down the Northeast coast to New Jersey and Long Island, and into deeper water off Virginia and North Carolina.

Water temperature is crucial throughout the lobster’s life, making the species acutely susceptible to warming oceans. When water tops 69 degrees Fahrenheit, the amount of dissolved oxygen required for them to breathe declines and the amount they require increases, causing physiological stress and even death. It’s likely that by midcentury, temperatures in warmer parts of the species’ range, including Long Island Sound, will consistently surpass the lobster-friendly limit, resulting in the loss of suitable habitat in those regions.

Even worse for those living at the edge of their comfort zone is an increase in extreme weather, which can lead to mass lobster mortalities. In 1999 rising water temperatures (not necessarily attributed to climate change) in Long Island Sound, followed by severe wind and rain, disrupted the balance of oxygen and salinity required for their survival, resulting in a major die-off, possibly as high as 75 percent. “The writing on the wall is that the Sound will become no longer hospitable for lobsters,” says Richard Wahle, a research associate professor at the University of Maine’s Darling Marine Center. On the flip side, warming in cooler areas, such as the Gulf of St. Lawrence, could boost populations by fostering more suitable nursery grounds, an earlier hatching season, a longer growing season, and more rapid growth.

For more profiles of species with a lot to lose in the face of global warming, read "Feeling the Heat," from Audubon's May-June 2010 issue.