Narragansett Bay's Mussel Blues: Hypoxia Wiped them Out

Timing can mean everything in scientific field work. Recall that back in 1987, UConn’s Barbara Welsh happened to be monitoring dissolved oxygen levels over Hempstead Sill, in Long Island Sound between Westchester and Nassau Counties, when a vast bloom of brownish algae led to the conditions that killed marine life and turned the western third of the Sound into a dead zone.

If she hadn’t been there, working on the Long Island Sound Study, people surely would have noticed the fish kills but nobody would have been collecting the data that explained why the fish were dying would and nobody would have been making the personal observations that added depth to the data.

A scientist named Andrew Altieri, who was doing research on Narragansett Bay’s mussels, got similarly lucky in 2001 during one of that estuary’s bad hypoxia events. He was working on his doctorate at Brown University at the time and he and a Brown professor, Jon D. Whitman, published the results of the research this week in the journal Ecology.

The bottom line is that Narragansett Bay had nine vast mussel reefs, covering 250 acres. When the hypoxia hit, in the summer of 2001, it killed an estimated 4.5 billion mussels.

The Altieri-Whitman article doesn’t appear to be on line yet, but Peter Lord, the Providence Journal’s environment reporter, has some terrific details in a story he wrote this week:

Altieri had no idea he would swim into an historic pollution event when he began his research in the fall of 2000. He wanted to study the ecology of mussel beds.

Typically mussels attach themselves to rocks or pilings. But Altieri found vast "reefs" of mussels on the Bay floor, holding themselves up by attaching to each other with their golden byssal threads.

He found more than 250 acres of mussel reefs. The biggest covered about 64 acres at the north end of Prudence Island. He also found sizable reefs just south of Warwick Point, at the north end of Jamestown, just off Hog and Hope islands, and at other places around Prudence Island.

"It was pretty impressive," said Altieri. "They were living reefs."

He found the mussel reefs provided habitat for other animals, served as a food resource for other animals such as starfish, and played a critical role in filtering algae from the water.

Altieri stopped diving for a few weeks during the summer of 2001 because of an ear infection.

When he got back underwater in August, he said, "It was immediately obvious that something catastrophic had happened."

The mussels had fallen into piles of dead shells, many covered with white bacteria. The starfish were gone.

Altieri and Witman estimated that 80 percent of the mussels were dead. (Quahogs can tolerate much lower oxygen levels.)

When they returned to study the reefs in the fall of 2001 and a year later, they found one reef gone and seven others dramatically depleted.

Without the mussels filtering algae from the water, future algae blooms could be worse, in turn causing more problems for other marine life, Altieri said.

"This mussel story is a great indication of what can happen in the Bay," Altieri said. "The mussels were canaries in the coal mine. Hundreds of other estuaries have the exact same problem."

You can read Lord’s story here.