Algal Identification

Harmful Algal Blooms

Harmful Algal Blooms in Maryland

​​Pfiesteria piscicida and Pfiesteria shumwayae

In 1997, fish kills were associated with toxic algal events on the lower Eastern Shore of Maryland. Toxic Pfiesteria was again isolated from cells collected at a fish kill event on Middle River in 1999. Since 1997 monitoring results have expanded the known distribution of Pfiesteria in the Chesapeake and Coastal Bays through the use of genetic probes created by Dr. David Oldach and colleagues at the University of Maryland. Biweekly monitoring updates on Pfiesteria activity are provided on DNR's website during the summer months to provide citizens and scientists with the latest status of monitored waterways.

Discovered in 1988 by researchers at North Carolina State University, Pfiesteria piscicida is believed to have a highly complex life-cycle with 24 reported forms, a few of which can produce toxins. A few other toxic dinoflagellate species with characteristics similar to Pfiesteria have been identified but not yet named. These are referred to as "Pfiesteria-like organisms," and they occur from New York to the Gulf of Mexico.

A natural part of the marine environment, dinoflagellates are microscopic, free-swimming, single-celled organisms, usually classified as a type of alga. The vast majority of dinoflagellates are not toxic. Although many dinoflagellates are plant-like and obtain energy by photosynthesis, others, including Pfiesteria, are more animal-like and acquire some or all of their energy by eating other organisms.

Learn more about Pfiesteria piscicida and Pfiesteria shumwayae in Maryland.