Climate Change and Bacteria in New England Waters

Climate change is playing a significant role in altering the marine ecosystem, making the waters of New England more inviting for harmful bacteria, particularly those that can be lethal. According to Hamer, “With warmer water temperatures moving further north, it allows Vibrios to survive, especially during summer months at latitudes they hadn’t previously reached.”

Indeed, the evidence is clear. Midsummer ocean temperatures around Woods Hole have increased by about 2.75 degrees over the years—in fact, from 2021 to 2025 compared to two decades ago. This data highlights a concerning trend for swimmers in the area.

“A couple degrees of difference can significantly increase bacterial growth,” Hamer noted. “If this trend continues, we can expect even more escalation in the next five to ten years.”

The oceans are currently absorbing more than 90 percent of the excess heat caused by climate change. This phenomenon is leading to rising sea levels as water molecules expand and glaciers melt. It’s also contributing extra energy to hurricanes—intensifying them—and creating a more suitable environment for specific bacteria.

Researchers have observed that the infections caused by Vibrio vulnificus are making their way further north as the climate continues to warm. Between 1988 and 2018, the number of wound infections from this bacteria rose from 10 to 80 cases annually in the eastern U.S. Moreover, the geographic reach of reported cases has moved about 30 miles north each year, as evidenced by a study published in 2023.

The study projects that by mid-century, specifically between 2041 and 2060, Vibrio vulnificus might be found as far north as Boston. In a scenario where greenhouse gas emissions, primarily from fossil fuel consumption, are not adequately curtailed, the bacteria could even extend into southern Maine by century’s end.

On a positive note, Vibrio vulnificus infections are still quite rare in Massachusetts. The state has recorded only seven cases over recent years, with just four linked to local exposure. However, Department of Public Health officials stress the importance of spreading awareness. When infections do occur, they present serious risks.

Statistics are worrying: one in five individuals with a Vibrio vulnificus infection may die, sometimes within just a day or two after falling ill. Others might face drastic outcomes, including amputations.

“There’s a rising number of individuals who are immunocompromised, whether due to health conditions or medications, putting them at greater risk for severe complications from the disease,” explained Larry Madoff, medical director at the state’s Department of Public Health. “And as the waters warm up, this risk becomes more pronounced.”

Madoff cautions those with pre-existing health conditions to think twice before swimming in the ocean if they have any cuts or scrapes, as well as when consuming raw or undercooked seafood—both avenues for bacterial infection.

“If I had a small scratch and dealt with severe liver issues, I would definitely stay out of the water,” he advised.

That said, he’s not completely discouraging beach outings. “It’s a fantastic way to cool off. We don’t believe folks need to shy away from the shoreline,” he added.