CHARLESTOWN, R.I. – Rain and sleet smack the surface of Ninigret Pond as oyster farmer Jules Opton-Himmel fumbles with a stalled outboard motor. Not much is going his way this morning.

He's under pressure to harvest on this mid-February day to make an on-time afternoon delivery to a local raw bar. On-board, he's trying to impress a top chef from one of Newport's most exclusive restaurants – and his pontoon boat is stuck in a field of slushy ice not even halfway out into the lagoon where he grows oysters.

"Everything going wrong – I'd say that's a pretty typical day," Opton-Himmel jokes, just moments before part of the outboard engine broke off, sinking into the icy water.

As New England's waters have become cleaner in recent decades, growers like Opton-Himmel have seeded the coast with oyster farms. As their efforts start to bear fruit, the ocean impacts of climate change may test the mettle of the burgeoning industry.

Boutique farmers, insatiable market

More than 350 oyster farmers now cultivate bottom leases in the shallow waters along the Northeastern seaboard, according to the Northeast Regional Aquaculture Center, up from handfuls 25 years ago. The rewards are great. With an insatiable half-shell market, gross profits are high and demand constant. But the challenges may be greater.

The Northeast's boutique oyster farmers must contend with the vagaries of New England weather. They must also deal with a host of challenges tied directly to the environment and potentially amplified by climate change, including warming waters, increasing ocean acidity and the spread of diseases that can decimate shellfish stocks.

Climate change poses important challenges to the industry's long-term viability. But to growers like Opton-Himmel, coping with the day-to-day quandaries of small business ownership and economic pressures of a crowded, premium market, the climate threat can feel abstract.

The same day that Opton-Himmel got stuck in the ice, oysterman Jim Arnoux, owner of Rhode Island's East Beach Farms, was across the lagoon dealing with a deer carcass frozen in the ice above his oysters. "You never know what you are going to get," he said. "Anything from random and chaotic to tedious dividing and sorting."

Ancient productivity

Thousand-year-old mounds of discarded oyster shells, called middens, that line the banks along parts of Maine's Damariscotta River attest to the productivity – and Native Americans' ancient appetite for – local oysters. Wild populations quickly declined as European settlers moved into the area. In the 1800s, a primitive aquaculture industry was born when harvesters started actively growing oysters on submerged plots, planting oyster larvae from remaining wild reefs.

In the early 1900s, at an industry peak, nearly 30,000 acres, roughly 30 percent of the entire bottom of Rhode Island's Narragansett Bay was leased out to oyster growers.

Throughout the first half of the 20th century, "environmental changes on an epic scale" helped decimate the industry, said Bob Rheault, executive director of the East Coast Shellfish Growers Association, and industry group. One of the pioneers of New England's oyster renaissance, Rheault founded Narragansett's Moonstone Oysters in 1986.

Untreated sewage and industrial waste flowed freely into the nation's waterways. Raw oysters were implicated in massive outbreaks of cholera and typhus. Whole harvests from Long Island to New England were smothered under tons of sand during the Great Hurricane of 1938. In the 1950's, shellfish parasites wiped out huge swaths of oysters in the mid-Atlantic.

Push to clean coastal waters

A push by federal and state agencies starting in the 1970s to clean up coastal waters helped elevate oysters from "something that was going to make you sick to something that was quite safe," Rheault said.

Cleaner waters and advances in aquaculture technique made oyster growing a viable business. Aquaculture of the past relied on taking oyster larvae from wild reefs. Today, most commercial oysters in New England come from hatchery-reared larvae, or seed, raised in shallow tanks called upwellers. Natural oyster populations remain at just 1 percent of historical levels.

The allure of the upscale raw bar or half-shell market – on which single oysters can retail for as much as $3 a pop – has enticed many a first-time oyster farmer.

Opton-Himmel is one such farmer. He started his operation, Walrus and Carpenter Oysters, in 2009 with a few cages on a 1,000 square-foot plot. The son of an artist, he grew up in Manhattan's Greenwich Village and as a child took frequent trips to the Adirondack Mountains. "I've always loved being outdoors," he said.

A graduate of the Yale School of Forestry, Opton-Himmel worked for the Nature Conservancy on shellfish restoration projects. Rhode Island's streamlined permitting process and clean water caught his eye.

He now farms three acres in Ninigret Pond, or about one million oysters. He hopes to get about 85 cents per oyster – except that, in a very good year, only 30 percent of his oysters will survive.

New England 'terroir'

While small, Walrus and Carpenter is average by New England oyster farm standards, where most growers run boutique farms that rely on name-branded marketing and distinctive flavors based on geographic location – what the wine industry would call "terroir."

While Opton-Himmel stands alone, other small growers, such as Arnoux have formed cooperatives with nearby farms to help increase their reach by sharing the expense of packing facilities, marketing and sales.

Rheault says a growing concern to New England's boutique farmers is increased competition from oyster farms to the south. "The industries in Virginia and Maryland are just taking off – we don't even know how big it is," he said.

In 2009, seeking to attract investment and rebuild its oyster industry, Maryland changed its leasing laws and made it easier for new oyster farmers to get a plot. "We've seen over 100 applications for new leases," said Don Webster, an aquaculture specialist with the University of Maryland Extension and chairman of the Maryland Aquaculture Coordinating Council.

Three years to market

Oysters grow faster in the slightly warmer waters of the Mid-Atlantic. In some parts of Virginia, oysters may be ready to harvest in a year. Farther north it may take two to three years to grow oysters that big.

Oyster connoisseurs say slow-growing, cold-water varieties taste better, and New England farmers certainly charge a premium price for their product. Yet Rheault and others fear that expansion in southern states could drive down prices for everybody, making oyster farming a hard go in New England.

Climate change, in the form of warmer waters and increasing ocean acidity, may exacerbate economic uncertainties.

"As a grower, shellfish disease is the biggest thing that I worry about. And that's closely linked to climate change," said Opton-Himmel.

MSX and Dermo are the most devastating oyster diseases on the East Coast. MSX, caused by a parasite, can kill up to 90 percent of an oyster crop when it strikes. Both are warm water diseases. A cold, hard winter generally knocks it back, but when winters are mild, oysters can succumb, said Dale Leavitt, an aquaculture specialist at Roger William University in Rhode Island. "We anticipate a higher incidence of these diseases as the environment warms," he said. Scientists have developed disease-resistant lines, though farmers typically cross a number of lines, some resistant, some not, for best production.

Seafood disease

Though these diseases do not pose a threat to human health, the warm-water bacterium Vibrio vulnificus does. Responsible for 95 percent of all seafood-borne deaths, according to an article published last year in the journal Microbial Ecology, the naturally-occurring bacteria historically has not been found in northern latitudes. But recent reports place it as far north as Alaska, said Barbara Brennessel, a biology professor at Wheaton College in Massachusetts and author of the book Good Tidings: the History and Ecology of Shellfish Farming in the Northeast (University Press of New England, 2008).

Even more alarming than the spread of disease, said Rheault, is the rate at which the ocean's chemistry is changing. As the globe warms, more carbon dioxide enters the oceans, acidifying the water. This spells trouble for shellfish that depend on a higher pH in order for their hard shells to form properly.

While ocean acidification has yet to plague the East Coast oyster industry, hatcheries in Oregon have struggled with persistent production failures, as oyster larvae fail to survive in more acidic waters.

"Carbon dioxide from the atmosphere is entering the ocean almost everywhere, but local environmental conditions can magnify its effects," said Sarah Cooley, a marine chemist at Woods Hole Oceanographic Institute in Massachusetts. "Ocean acidification effects will likely become obvious on the East Coast within the next few decades," she said.

Abstract worry?

But when you are out on a boat, trying to make a living off the sea, 20 years can seem like ages.

"Climate change is not something I worry about on a daily basis, but I am becoming more aware of it," said Arnoux, who started growing in 2005 in the same lagoon where Opton-Himmel tends his plot. Still, he's in it for the long haul, and Arnoux sees himself preparing for an uncertain future by branching out into other species, such as scallops, across several locations.

Opton-Himmel doesn't see himself exclusively farming oysters either. Though he continues to expand his business, he does some environmental consulting on the side.

Back on shore, warm thermos in hand, he pauses to mull the need for a Plan B before packing up his truck and heading to Maine for a few days to work on a consulting project. "So many things could go wrong. It's so risky."

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.