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Name the Bay Critter Contest...And the Mystery Surrounding a Controversial Cell


Spiky space alien with a bad hair day? Christmas tree ornament from uncle Mort?  The first reader to correctly identify this Chesapeake Bay critter will win a free Chesapeake Bay Foundation T-shirt.  Enter guesses as comments below.  Ready, set, go!

UPDATE:  It is, in fact, pfiesteria....the enigmatic, controversial "cell from hell" that was associated back in 1997 with fish kills on the Pocomoke River and other Eastern Shore waterways and dozens of reports of illnesses and memory loss in humans.  The first reader to guess the correct answer was Wendy Scheafer!  Congratulations, Wendy.  Send your mailing address and T-Shirt size to me at and I'll mail you your prize.

Pfiesteria is a single-celled organism, part plant and part animal, that propels itself through the water with a pair of whip-like arms (two flagella, thus the name "dinoflagellate.")  The organism is shown above in its encysted form, in a photo courtesy of the Maryland Department of Natural Resources. 

Interestingly, in the years since the 1997 fish kills that provoked widespread media coverage and inspired a law in Maryland designed to reduce agricultural runoff pollution, the mystery surrounding pfiesteria has only deepened.

There is no doubt that fertilizer runoff into waterways needed (and still needs) to be reduced, because these nutrients feed sometimes toxic algal blooms and fish-killing low-oxygen "dead zones."  But over the last decade, at least one researcher has suggested that it was a different dinoflagellate, Karlodinium veneficum, that actually killed the fish in the Pocomoke River, while the Pfiesteria was present and feasted on the dead fish afterwards.  The issue of what was responsible for the fish kills and human illnesses is not yet resolved, with several strong opinions on various sides of the debate.

Karlodinium, like pfiesteria, eat other algae -- so they can become more numerous when nutrient pollution and warm conditions stimulate algal blooms.  So, from a public policy perspective, reducing runoff pollution would reduce the chance of a fish-killing karlodinium bloom, too.

Meanwhile, it remains unclear what caused the dozens of reported illnesses along the Pocomoke River back in 1997, including the reports of memory loss. 

By Tom Pelton

Chesapeake Bay Foundation


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Is it a type of phytoplankton that helps create anoxic zones?


Dinoflagellate cyst?

this is a genus of heterotrophic dinoflagellates, been associated with harmful algal blooms and fish kills. The actual name is Pfiesteria complex organisms (PCOs). They were claimed to be responsible for large fish kills in the 1980s and 1990s on the coast of North Carolina and in tributaries of the Chesapeake Bay.

Encysted form of dinoflagellate

Pfisteria piscicida

Could this be a jelly fish polyp?

Pfiesteria complex organism (PCO)


That would be Pfisteria piscicida

Frost/ice crystal

Was the answer of "dinoflagellate cyst" really not correct?? I was actually apprehensive about calling it Pfiesteria spp. due to other heterotrophic dinos also encysting... :(

Thanks very much for playing, A.T. But, sorry, I was looking for the name of which dinoflagellate it is, and Wendy was the first to give that name as pfiesteria.

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