Warming waters affecting bay scallops, SBU researchers confirm

Warming waters tied to increasing summer heat waves have led to a reduction of dissolved oxygen in the Peconic Bay and other estuaries, with catastrophic effects for the bay scallop, a new paper concludes.

While researchers have been examining a range of potential factors in the Peconic Bay scallop die-offs for the past four years, including parasites, algal blooms and predators, the consistent trend through that time has been higher water temperatures and a corresponding reduction in oxygen levels. Those factors have stressed bay scallops during the summer spawning season, putting them further at risk.

A new paper by top Stony Brook University professors in the journal Global Change Biology formalizes the findings. A summer heat wave that lasted for just over a week in 2020, for instance, coincided with repeated episodes of lower dissolved oxygen, stressing the scallops, according to Christopher Gobler and Stephen Tomasetti of Stony Brook University’s School of Marine and Atmospheric Sciences.

They found “extreme summer temperatures, becoming more frequent under climate change, exacerbate the vulnerability of bay scallops to environmental stress and have played a role in the recurrent population crashes."

“The last three or four summers have been warmer than in the past, particularly around the time the scallops are spawning,” Gobler said in an interview Thursday. The research covers trends along the Northeast coast to Massachusetts, an area that he said is seeing outsized impacts from climate change.

“Global warming is happening at an uneven pace in space and time,” Gobler wrote. “It just so happens that summer water temperatures in the Northeast are increasing at a rate more than three times the global average, leaving organisms adapted to cooler temperatures endangered.”

The team examined years of records of water and air temperatures and oxygen levels in the bays and combined the research with satellite temperature records and its own research in the field and the lab to set the base for its conclusions. Monitoring included scallop heartbeat rates, which vary with temperature. Those records were able to establish that bay scallops have become “increasingly susceptible to the combination of high temperatures and impaired water quality.”

Gobler said while warming and cooling trends can be cyclical, the trend line points to warming and he’s not holding out hope that the bay scallops will make a comeback. He wonders if bay scallops in Massachusetts waters won’t eventually be impacted.

“Long term, the northern bay scallops are not long for our waters,” he said, noting a similar trend that saw lobsters eventually vanish from Long Island Sound, for cooler waters north and east. Indeed, there’s some evidence bay scallops are doing better in cooler waters to the east, some fed by larger waterways. But “there’s virtually no harvest from within [western] Peconic Bay proper,” he said.

Solutions to the problem are still being considered. Stony Brook has seen strains of bay scallops that are resistant to certain parasites, and Gobler said it’s possible those with greater resistance to warming temperatures could be identified.

But he added, “This is a climate change issue and the climate is going to continue to change. Sometimes people may hear the term and it’s hard for them to grasp. But this [scallop die-off] is one of the things that brings home what it means to be living in a warming world.”

By Mark Harrington

mark.harrington@newsday.comMHarringtonNews

Mark Harrington, a Newsday reporter since 1999, covers energy, wineries, Indian affairs and fisheries.