The Maine Department of Marine Resources has formalized its decision to close a 7-square-mile area at the mouth of the Penobscot River to lobster and crab harvesting because of concerns about mercury contamination.

The department issued an emergency ruling in February that immediately closed the area for at least two years. That emergency ruling was valid for only 90 days. During that time, the state fielded public comments.

On Wednesday, the state said it had decided to formalize the two-year closure.

“We’ll spend two years monitoring the area. Then we’ll decide what to do next,” said Department of Marine Resources spokesman Jeff Nichols.

The closure extends from Wilson Point, just north of Castine Village, across to Fort Point in Stockton Springs and north into the Penobscot River. The area is a small fraction of the 14,000 square miles in the Gulf of Maine where lobsters are harvested.

The Department of Marine Resources said previously that it became aware of hazardous mercury levels in lobsters in November after it examined findings from a federal court-ordered study.

That study related to a federal lawsuit filed by the Maine People’s Alliance and the Natural Resources Defense Council against Mallinckrodt Inc., the current owner of a plant that was used by HoltraChem Manufacturing Co.

The 10-year study, completed by a team of three scientists in 2013, showed that mercury contamination in the sediment and wetlands has been declining slowly since HoltraChem began discharging mercury waste directly into the river in 1967, but is “still high enough to be hazardous” to plants and animals and the people who eat them.

Lobster is Maine’s most lucrative fishery. In 2013, nearly 126 million pounds of lobster was harvested in the state.

Jessica Hall can be contacted at 791-6316 or at:

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@JessicaHallPPH