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Impacts of Pfiesteria: Outbreaks could substantially reduce tourism revenues, Sea Grant researcher says

Atlantic menhaden with Pfiesteria piscicida toxin-related lesions.
Burkholder Laboratory
NEWARK, DE.--When toxic Pfiesteria piscicida microorganisms invade recreational waterways, summer tourism and seafood sales can suffer, a researcher with the University of Delaware Sea Grant College Program reported today in a briefing at the National Press Club, Washington, D.C.

A new survey of 3,500 coastal residents from New York to the Carolinas–conducted by UD Sea Grant Marine Advisory Service Director James M. Falk–reports that Pfiesteria outbreaks may dramatically affect consumers’ seafood eating habits and travel choices.

"According to our survey," Falk points out, "a Pfiesteria outbreak could reduce tourism in an affected area by at least 40 percent, significantly impacting coastal communities."
Seafood sales also may plummet as a result of Pfiesteria outbreaks. Nearly two-thirds of Falk’s survey respondents said they would eat less locally harvested seafood if the microorganism had been reported in their state waters.

Toxic zoospore of Pfiesteria piscicida.
Burkholder & Glasgow, 1997
To gauge public perceptions and attitudes related to Pfiesteria, Falk mailed a four-page, 30-question survey to residents of Delaware, Maryland, Virginia, North Carolina, New Jersey and New York–states most vulnerable to the microorganism. Some 26 percent of the questionnaires (excluding undeliverable envelopes), or 789, were returned to Falk.
"The goal," he explains, "was to better understand what Mid-Atlantic residents know and think about Pfiesteria, and how it’s affecting their lives."

What is Pfiesteria?

The vast majority of respondents–90 percent–said they had heard of Pfiesteria. When asked to describe Pfiesteria by selecting one of five definitions, however, participants’ answers were "all across the board," Falk says.

In fact, he points out, Pfiesteria is a form of microscopic algae–a single-celled dinoflagellate–which propels itself through the water with whip-like projections called flagella. A primitive life form with more than two-dozen life stages–many of them benign–Pfiesteria probably has been present in the environment for thousands of years. Excess nutrient runoff from residential, agricultural and industrial areas may, according to some scientists, now be helping toxic forms of Pfiesteria to increase dramatically or "bloom," Falk explains.

Toxic Pfiesteria can paralyze and feed on fish, leaving telltale sores and bleeding lesions in their flesh. The problem has been particularly troublesome in sheltered estuarine waters in North Carolina and Maryland, where bait fish such as menhaden have been killed by the microorganism.

Is it Harmful?

"Ninety-five percent of all survey respondents said they think that Pfiesteria can be harmful to them," Falk says. "From a human health standpoint, the public is very, very concerned about Pfiesteria."

To pinpoint the exact nature of those concerns, the UD Sea Grant survey included five statements describing potential risks associated with Pfiesteria. Respondents were invited to check multiple statements, indicating all those believed to be true.

Some 66 percent said they think Pfiesteria harms the environment and, therefore, could indirectly harm people. In addition, 65 percent said they believe Pfiesteria can harm those who eat affected seafood. More than half, or 54 percent, said they believe Pfiesteria can harm swimmers or waders in the water, and 46 percent were concerned about people fishing in boats. Only 4 percent said that Pfiesteria toxins in the air can be harmful, "a potentially worrisome finding," Falk notes, "since airborne transmission of the toxins has been proven to cause human illness in laboratory settings."

Consumers have great concern about eating seafood harvested from affected waters, although David Green, head of North Carolina State University’s Seafood Laboratory, has found "no scientific evidence linking seafood-borne illness with Pfiesteria."

Fifty-nine percent of respondents indicated that a report of Pfiesteria in their state waters would reduce their seafood consumption. When asked if seafood from affected waters is safe to eat if it’s properly handled and prepared, nearly half of the respondents (45 percent) said, "No." Another 31 percent were unsure.

Pfiesteria’s human health impacts are not yet fully understood. Reports by people fishing, researchers and those riding through fish kills on boats have linked exposure with skin lesions, short-term memory problems, headaches and other symptoms. Consequently, Falk says, it’s best to leave an area where fish can be seen floating on the water’s surface. Consumers are also advised to thoroughly cook finfish and shellfish, and to avoid any seafood with obvious evidence of sores or diseases. He also recommends contacting state public health and natural resource officials whenever Pfiesteria is suspected.

Pfiesteria and tourism

Pfiesteria’s impact on summer travel plans was a particular focus of the UD Sea Grant survey. "If you made plans to visit a beach or coastal area for pleasure and heard there was a Pfiesteria outbreak," the survey asked, "how would it affect your travel plans?"

When asked to select only one of six responses, three-fourths said they would either go somewhere else, or at least change some of their recreational activities. Only 11 percent of the 789 people in the sample reported that a Pfiesteria outbreak would have no impact at all on their travel plans.

Specifically, 32 percent said they would still visit an affected area, but would change some of their activities. Another 29 percent said they would change their travel plans to avoid the affected coastal area. Six percent said they would no longer go to that particular area at all, and 5 percent said they would avoid coastal areas altogether. Seventeen percent were unsure how Pfiesteria would affect their travel plans.

"If you add up all of these categories," Falk notes, "seventy-two percent said they would either avoid the beach or change some of their plans when they got there. And, that 17 percent who said they were unsure could join the more concerned group, meaning that a majority of all beachgoers could potentially alter their plans."

Even if those responses are interpreted very conservatively, Falk says: "It’s clear that a Pfiesteria outbreak can seriously jeopardize tourism revenues. In Delaware’s Sussex County, for instance, an estimated 2.3 million visitors brought $342 million into the area in the summer of 1998. If a Pfiesteria outbreak were to occur there, the county could see a substantial loss of visitors and their spending power. Clearly, Pfiesteria is a real economic issue, as well as a health and environmental problem."

Most respondents, or 85 percent, agreed that money spent by state governments to help correct any problems caused by Pfiesteria is well spent, Falk reports. "And, only a third of all respondents reported that they had enough information about Pfiesteria to make informed decisions that may affect them. That’s a strong endorsement for continued government efforts to prevent Pfiesteria outbreaks, and to increase awareness of the environmental problem," he concludes.

Contacts: UD Tracey Bryant, (302) 831-8185,; or
Ginger Pinholster (302) 831-6408,
Sea Grant–Ben Sherman, (202) 662-7095,

Sept. 27, 1999