In a nasty twist of fate, blue mussels that were busy cleaning up Rhode Island's Narragansett Bay were killed by an expanding dead zone.
Dead zones are usually blamed on excess nutrients from fertilizers and livestock. But the "demand-side" is a neglected human impact that creates or worsens dead zones. Over-harvest of oysters and clams that eat plankton has reduced the ability of coastal waters to consume and limit the plankton blooms that create dead zones.
Scientists were studying a lucky mussel-building boom in summer 2002, that was a miniature version of the once-grand bivalve empire (mussels, clams & oysters). They noted the "muscular" cleaning effect of some impressive mussel reefs and the clear water that resulted. But, alas, it was too good to last. A plankton bloom overwhelmed the bay and created a massive smack-down of low oxygen that killed the mussels and many other animals that couldn't flee. The bay will probably take a decade to recover.
Maybe this is a cause for California's "mussel building" Governor, Arnold Schwarzenegger.