Citing increased levels of bacteria, the state Department of Environmental Conservation is closing or limiting the harvest of shellfish in about 1,840 acres of Long Island bays and harbors.

The DEC announced Thursday it is changing the designated areas to harvest shellfish in Brookhaven, Huntington, Islip, Smithtown, Riverhead, Southampton, Southold, East Hampton and Oyster Bay.

Affected areas will be closed for the harvest of clams, mussels, oysters and scallops "either year-round or seasonally," the DEC said.

According to the DEC, an analysis of water quality showed increased levels of fecal coliform bacteria, which can enter the water from a "variety of human, animal, cesspool and storm water sources."

Consuming shellfish harvested from these areas can cause illness, the agency said.

Effective immediately are these changes:

In the towns of Islip and Brookhaven, on the South Shore: In Patchogue Bay, about 1,028 acres will be closed to shellfish harvesting from May 1 through Sept. 30.

In the towns of Smithtown and Brookhaven, on the North Shore: In Stony Brook Harbor, about 300 acres, closed from May 1 through Dec. 31.

In the Town of Brookhaven: In Mount Sinai Harbor, about 200 acres, closed from May 1 through Oct. 31.

In the towns of Huntington and Oyster Bay: In Cold Spring Harbor, about 99 acres, closed from May 1 through Oct. 15.

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In the towns of Riverhead and Brookhaven, on the North Shore: In the Long Island Sound, about 72 acres, closed year-round.

In the towns of Southold and Riverhead: In Great Peconic Bay, about 65 acres, closed year-round.

In the Town of Southampton: In Shinnecock Bay, about 60 acres, closed from May 1 through Nov. 30.

In the Town of East Hampton: In Accabonac Harbor, about 20 acres, closed year-round.

Learn more about shellfish safety at www.dec.ny.gov/outdoor/345.html.