Health Services

Paralytic Shellfish Poisoning (PSP)

In the northeastern United States, paralytic shellfish poisoning (PSP) is an illness caused by eating shellfish contaminated with a dinoflagellate marine algae (Alexandrium) that contains a powerful biotoxin called saxitoxin.

Is paralytic shellfish poisoning (PSP) caused by "red tides"?

“Red tide” is a reference to the reddish brown discoloration that is imparted to the water column by an algal bloom, and is typically associated with one of many dinoflagellate species. In New York and New England waters, Alexandrium is a dinoflagellate that causes red tides, and is the principal organism associated with PSP. However, it is not necessary for a red tide to be present for shellfish to be contaminated with PSP. Bivalve mollusks, including clams, mussels, scallops, and oysters, gather their food by filtering algae and other plankton from the water. Because this causes the algae to become concentrated in their systems over time, the mollusks can be poisonous even when there is insufficient numbers of dinoflagellates present to cause a visible red tide.

What are some symptoms of PSP?

Symptoms of PSP will depend on the amount of toxin ingested, and can progress from tingling of the lips and tongue, to numbness of the face, neck and limbs, loss of muscular control, followed by difficulty breathing.

Has PSP been found in Suffolk County waters?

Primarily, PSP is associated with shellfish taken from waters north of Long Island, including those of Maine, Massachusetts, and Connecticut. Previous investigations done in Suffolk County waters however, have found Alexandrium to be present although no cases of paralytic shellfish poisoning have been documented. Studies done by Anderson et al. (1982) revealed the presence of Alexandrium cysts in the sediments of 6 of 31 Long Island estuaries examined. Schrey et al. (1984) found vegetative cells in 46 of 115 Long Island estuaries and inlets sampled during the spring of 1983. The toxin content of cell cultures grown from the cysts found by Anderson et al. however, was low. This agreed with a study done by Miranda et al. (1985) who noted that the toxin content of Alexandrium isolates along the east coast decreased from north to south.

More recently, studies conducted by the NYSDEC have noted almost annual Alexandrium blooms in the Huntington-Northport Bay complex (2006, 2008-2012) that all resulted in shellfish bed closures due to presence of the toxin. In 2012, PSP was also detected in Shinnecock Bay, Mattituck Inlet and Sag Harbor Cove.

Does Suffolk County monitor local waters for PSP?

In response to the early findings mentioned above, a survey was undertaken by the Office of Ecology from 1986 through 1989 in an effort to characterize the population dynamics of Alexandrium in eleven Suffolk County embayments, and coincidentally, determine the levels of PSP toxin present (by mouse bioassay) in mussels placed at each site (Nuzzi and Waters, 1989). Of the eleven sites studied, PSP toxin was only found in mussels placed at three sites in the western Peconic Estuary (Reeves Bay, Terrys Creek, and East Creek). The public health standard of 80 ug of toxin/100 g of shellfish meat was exceeded on one occasion.

In the spring of 2000, a second PSP survey was initiated by the Office of Ecology that involved the monitoring of nine sites in the Peconic Estuary (including the Peconic River, Reeves Bay, Terrys Creek, Meetinghouse Creek, East Creek, James Creek, Deep Hole Creek, Cold Spring Pond, and Bullhead Bay). Sampling was repeated in the fall at the same locations; results for all samples collected were negative. During 2001, the survey was performed at locations in Shinnecock Bay, and Moriches Bay including Weesuck Creek, Quantuck Creek, Beaverdam Creek, Seatuck Cove, Hart Cove, and the Forge River. Positive results were found at all locations in the spring (but not the fall), although the levels of toxin detected were well below health standards.

As the NYSDEC has now developed their own PSP program, Suffolk County no longer conducts routine monitoring for the organism.

Where can I find more information on PSP?

For more information, visit any of the links below or contact the Office of Ecology at (631) 852-5760.


Nuzzi, R, and Waters, R.M. 1993. The Occurrence of PSP Toxin in Long Island, New York, USA. Toxic Phytoplankton Blooms in the Sea. pp. 305-310.[Upload Pending]

Schrey, S.E., Carpenter, E.J., and Anderson, D.M. 1984. The Abundance and Distribution of the Toxic Dinoflagellate Gonyaulax tamarensis in Long Island Estuaries. Estuaries 7 (4B), 472-477. [Upload Pending]

NYSDEC Harmful Algal Blooms and Marine Biotoxins

NYSDEC Marine Biotoxin Monitoring Program