A diatom Pseudo-nitzschia sp. was detected at 6,254 cells/ml in a water sample collected from Pocomoke Sound on April 15. Threshold levels of interest are typically 200-500 cells/ml. Maryland Department of Natural Resources field personnel collected the sample during routine monitoring of the Chesapeake and Coastal bays at the long-term water quality station EE3.3. The sample was sent to the Dr. Dave Carons laboratory at the University of Southern California for toxin testing.

The sample tested positively toxic at extremely low levels of 13 picograms domoic acid/ml. For comparison, the concentration detected is about 100-250 times lower than areas in Washington State where domoic acid has presented a human health risk for possible shellfish poisoning. Laboratory testing of Pseudo-nitzschia seriata cultures derived from samples collected from the Choptank River in 2002 provided the first evidence that this diatom was capable of expressing toxicity in the Chesapeake Bay.