The state Department of Environmental Conservation Thursday afternoon prohibited the harvesting of shellfish, whelks, conch and moon snails in a 31-acre area of James Creek in Southold after a marine biotoxin was detected.

This is the first time the DEC has closed down James Creek because of saxitoxin, which can cause nausea, vomiting, headaches, vertigo, respiratory failure and even death if high levels are ingested by humans.

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This is the third saxitoxin closure issued on Long Island since May 6.

On May 6, DEC closed 100 acres in Meetinghouse and Terry Creeks in Riverhead. On May 7, the agency closed 3,800 acres in western Shinnecock Bay, west of Ponquogue Bridge.