The Maine Responder, a massive pollution-control vessel that has been moored in Portland Harbor for more than two decades, has been pulled from service because its operator has lost funding and the risk of an oil spill in the region has dropped because of declining tanker traffic to the Portland Pipe Line Corp.

News of the change Monday surprised many who work to ensure the safe operation of the harbor and are concerned about protecting Casco Bay and shipping routes that the vessel has covered from Maine to Massachusetts and beyond.

The Marine Spill Response Corp. of Herndon, Virginia, confirmed Monday that the 210-foot-long vessel, which has docked in Portland since 1995, had been removed from service and its six crew members had been told they will lose their jobs.

Marine Spill Response will keep the boat in the water at Union Wharf and will continue to operate 10 other spill-response vessels, so several shipping companies and other facilities in the area that contract for its services will be able to maintain Coast Guard-approved spill-response plans, said company spokeswoman Judith Roos.

“(The Maine Responder) is being removed from active service as of today,” Roos said in a phone interview while in Portland. “We will continue to be able to meet our customers’ planning obligations in this sector even without the Maine Responder.”

Roos said the harbor has a “lower risk profile” because “trading patterns have shifted” in recent years, but she declined to draw a direct connection to the dwindling flow of the Portland Pipe Line, which delivers foreign crude from its ocean terminal in South Portland to refineries in Montreal.

“There are fewer tanker vessels trading into this area,” Roos said. “The (Maine Responder) will be deactivated with the potential to be reactivated should trading patterns change.”

Roos wouldn’t say how much it cost to operate the Maine Responder.

Peter Milholland, longtime staff member at Friends of Casco Bay, called the decision to suspend the service “shocking.” As pilot of the organization’s baykeeper’s boat, Milholland has participated in numerous spill-response drills and assisted in the cleanup after the 1996 crash of the tanker Julie N, which dumped 170,000 gallons of oil into the harbor after striking the former Portland Bridge.

“It will be a big loss to our area,” Milholland said. “There are a lot of other threats to our waters. There are other vessels that come through with other (petroleum) products, and lots of other boats with the potential for having problems, including cruise ships.”

CRUDE OIL DELIVERIES FALLING

The pipeline has nearly shut down in recent months as demand for foreign crude has fallen in the wake of booming tar sands oil production in Alberta, Canada. The pipeline received no oil deliveries from January through May this year, then took in nearly 1.4 million barrels in June, according to the latest data available from the Maine Department of Environmental Protection.

Pipeline officials declined to provide recent shipping data, so it’s unknown whether additional crude deliveries arrived in July and August. The pipeline transported more than 22 million barrels in 2015, down from 32.6 million barrels in 2014, according to the DEP.

“(The pipeline) remains open for business, supporting its customers, the community (and) employees … and continuing the safe and excellent operation it has long been known for,” spokesman Jim Merrill said in a prepared statement.

Merrill noted that the pipeline company has filed a federal lawsuit against the city of South Portland, challenging its 2014 ban on crude oil exports, a measure intended to protect air quality that also effectively stops the pipeline company from possibly reversing its flow in order to export tar sands oil from Canada.

The Marine Spill Response Corp. is a nonprofit, Coast Guard-classified “oil spill removal organization,” according to the company’s website. It was formed after the Oil Pollution Act of 1990, which was passed by Congress following the Exxon Valdez oil spill in Alaska. It is the largest emergency response organization of its kind in the U.S., offering oil spill cleanup services that mitigate environmental damage.

Shipping and trading companies that belong to the Marine Preservation Association, a separate nonprofit membership corporation, contribute a certain percentage of their receipts to operate the company and meet its capital needs.

HONORING LEASE AT UNION WHARF

Marine Spill Response has held a lease at Union Wharf for 21 years, said Charlie Poole, president of the Proprietors of Union Wharf.

Poole declined to comment on the company’s plans for the Maine Responder, other than to say that “they have a lease and they have honored their lease.”

The Maine Responder is one of 15 responder-class oil spill vessels operated by the Marine Spill Response Corp. across the U.S. In addition to a helipad, it has radar technology and infrared cameras that can detect oil in the water, hauls a 2,640-foot oil-containment boom and is capable of skimming and recovering 444,000 gallons of oil and water per day. The nearest vessel of its kind is in Perth Amboy, New Jersey, also operated by Marine Spill Response.

Crew members of the Maine Responder could fill job openings elsewhere in the company, Roos said. The company will keep five staff members in Portland. Vessels still operating out of Union Wharf include an MSRC 620 skimming barge and a 30-foot Kvichak Marco skimming vessel.

Wyman Briggs, the spill response preparedness specialist with the Coast Guard in South Portland, was among several local officials who were surprised to learn about the Maine Responder’s fate.

“It’s an unfortunate loss,” Briggs said. “It’s a very capable vessel. There’s not another one of its size in this area. Obviously we always prefer to have more response capability.”

Briggs said the Coast Guard will likely review the spill response plans of companies who have contracted for the services of Marine Spill Response.

Milholland noted that several other agencies also provide spill-response services, including the Coast Guard, the DEP and private contractors, such as Clean Harbors.

Acting Harbor Master Kevin Battle and South Portland Fire Chief Jim Wilson also were surprised to learn that the Maine Responder was being pulled from service.

Wilson said regional officials were scheduled to hold a tabletop spill-response drill Sept. 7. Now they’ll have a new factor to consider.

“Anytime you reduce a capability to respond, you have to make sure you can still respond adequately,” Wilson said. “We’ll probably get a good idea of the change in our capability when we meet next month.”

Staff Writer Penelope Overton contributed to this report.