The Gulf of Maine coastline, historically home to one of the richest shellfish populations in the U.S., is undergoing a dramatic change, with once-flourishing wild blue mussels all but disappearing, according to a study led by University of California, Irvine ecologists. After comparing contemporary survey data with 40 years of historical benchmarks, Cascade Sorte, assistant professor of ecology & evolutionary biology at UCI, and colleagues from around the U.S. report that the blue mussel numbers have declined by more than 60 percent along the gulf coastline, which stretches from Cape Cod north to the Canadian border. The mussels used to cover as much as two-thirds of the intertidal zone, but they now cover less than 15 percent.

Among the suspected reasons for this are warming oceans and increased human harvesting, Sorte said. Elevated air and water temperatures push the mussels out of their comfort zone, heightening physiological stress and, ultimately, mortality rates. Study results appear in Global Change Biology. Link to study: http://onlinelibrary.wiley.com/doi/10.1111/gcb.13425/full

"The Earth is in the midst of a biodiversity crisis," Sorte said, "and the Gulf of Maine is one of the fastest-warming areas of the global ocean, so the impacts of ocean warming are likely to happen much sooner there."

Blue mussels play an important role as filter feeders, removing bacteria, heavy metals and toxins from the water. They are a foundation species in the intertidal community that create habitat and enlarge the diversity of life supported by a locale. Their decline is of great concern, Sorte added, because it could precipitate "cascading extinctions" among other species.