PFIESTERIA PISCICIDA: Ichthyotoxic Estuarine Dinoflagellate



PFIESTERIA PISCICIDA: Ichthyotoxic Estuarine Dinoflagellate

Professor D. Rahni

Env. Law 802

December 7, 1999

This paper reports on and discusses a newly-discovered (1991) and classified single-celled organism called Pfiesteria piscicida and its morphologically-related organisms (MRO's) (as yet unclassified). In the early 1990’s, coastal estuaries in North Carolina experienced massive fish kills of unknown origin. Subsequently these fish kills were attributed to Pfiesteria by Dr. JoAnn Burkholder of North Carolina State University.

Since their discovery, these MRO’s have been found in coastal waters from the Delaware Bay to the Gulf Coast of Alabama, and have caused fish kills and human health problems in North Carolina and Maryland. They are part of a growing phenomenon broadly referred to as Harmful Algal Blooms (HAB’s), which is affecting fish and mammal health in coastal areas worldwide. While their causes are not conclusively proven to be related to human effects on the environment, there is persuasive evidence suggesting a strong link between algal blooms and excessive nutrient presence: nitrogen and phosphate pollution in coastal waters.

What Is It?

Pfiesteria is an ichthyotoxic dinoflagellate. Dinoflagellates are aquatic, motile, single-celled planktonic organisms. They move in the water by means of the whiplike appendages (flagella) that they use for swimming in some of their life stages. Ichthyotoxic means harmful to fish, and is derived from the Greek word for fish (ichthys).

There are nearly two thousand species of dinoflagellates, which take many different forms. Many dinoflagellates, like Pfiesteria, are considered “harmful algae” based on their toxic effects during algal blooms like the so-called “red tides”. The term “harmful algae” refers to true algae, which are primitive plants that make chlorophyll and get energy by photosynthesis, as well as to various single-celled creatures that look like algae but behave differently.

Pfiesteria combines some of the attributes of true algae, some of the characteristics of other toxic dinoflagellates, and aggressive predatorial behavior towards fish prey. Pfiesteria's name is derived from the name of a well-respected phycologist, Dr. Pfiester, the Latin word for fish (piscis) and the Latin suffix for killer (-cida) (e.g. fratricide, matricide

and patricide). In 1984, there were 22 known species of toxic dinoflagellates; in 1997 there were more than 60.[1]

Life Cycle

Pfiesteria differs from its cousins by virtue of its complicated life cycle. It can change into at least 24 different forms, depending on environmental conditions and the amount of prey organisms in the water.[2] It can vary in size from 4 uM to 450 uM. These shape and size changes can take place in as little as 10 minutes.[3] With no fish prey in the surrounding water, the cells stay either in the form of amorphous amoebae that stay in the bottom mud, cysts of various sizes that remain dormant, protected by a tough coating of armor-like “thecal” plates, or swimming cells known as nontoxic zoospores.

When fish arrive, these zoospores become toxic, and cysts and amoebae change to nontoxic zoospores which in turn become toxic. The toxic zoospores emit toxins that act to stun the fish and damage their skin. They also feed on the substances generated by the damage inflicted on the fish skin.[4] And they reproduce asexually, producing gametes that can combine to create planozygotes. The planozygotes and gametes join in the feast on the dead or dying fish. Once the fish is dead, the Pfiesteria return to the form of amoebae that feed on the carcass.

If no fish are present in the water, but algae are present, the toxic zoospores and gametes revert to nontoxic zoospores and amoebae feeding on the algae. If algal prey is abundant, the nontoxic zoospores may multiply, creating more potentially-toxic attackers should fish swim into the area.[5]

Pfiesteria is also capable of consuming algal cells and stealing their chloroplast, a phenomenon called cleptochloroplasty.[6] This gives Pfiesteria the capacity to produce energy from sunlight. In the absence of fish prey, Pfiesteria may also assume the form of cyst-like zygotes.

Where Is It?

In 1988, a doctor at the veterinary school of North Carolina State University called JoAnn Burkholder. Tanks of fish used for testing were dying with no visible cause. After a tank of fish died, the lab workers regularly cleaned out and dried the tank. But when fresh water and new fish were added to the tank, the same cycle happened.[7] Dr. Burkholder, a botanist by training, began to study the water to see what could be causing the deaths. She and her assistant isolated a dinoflagellate that seemed to flourish in the presence of fish and to cause the fish to die.

Three years later, during a massive fish kill in the Pamlico Estuary on North Carolina’s coast, Dr. Burkholder looked at a water sample from the Pamlico River and realized it contained the same dinoflagellate that had apparently been causing the death of the lab fish.

After consulting with staff at North Carolina’s Department of Environment, Health and Natural Resources she learned that samples of water taken from fish kills in North Carolina since at least 1985 had contained the same dinoflagellate.[8]

Since 1991, Pfiesteria or its MRO’s have been identified as being present at fish kills all along the east coast of the United States, in Florida and on the Gulf Coast of Alabama. From 1992 to the present, Pfiesteria were identified in the lower Eastern Shore of the Chesapeake Bay in Maryland, and in various fish mortalities at laboratories and culture ponds at fish farms.[9]

Pfiesteria have a wide salinity tolerance and a wide temperature tolerance.[10] They prefer calm waters, retreating into their non-toxic cyst stage in water that is not brackish. There is considerable scientific consensus that there is a strong connection between MRO blooms and overloads of nutrients like nitrogen and phosphorus.[11] This may be stimulation directly or indirectly by creating an abundance of algal prey.[12]

A Maryland Blue Ribbon Citizens Action Commission Report (the “Cambridge Consensus”) and a subsequent report by a group of aquatic ecologists, chemists, biologists and other scientists at the University of North Carolina’s Water Resources Research Institute (the “Raleigh Report”) both conclude that nutrient loading increases the risks of toxic outbreaks of Pfiesteria and MRO’s and the resulting fish kills.[13]

In the Cambridge Consensus, scientists estimated that agriculture accounts for 70 percent of the nitrogen pollution and 83 percent of the phosphorus pollution on the Maryland shore. And in Florida, an outbreak of a dinoflagellate-induced fish kill, by an MRO named Cryptoperidiniopsis, was linked to the release, by state and federal water managers, of billions of gallons of polluted floodwater from Lake Okeechobee into the Indian River.[14]

Nutrient loading as a cause of toxic outbreaks is especially significant in light of the rapid growth of feedlot operations in both Maryland and North Carolina in the last decade.[15] North Carolina is one of the largest swine and poultry-producing states in the USA. In 1996, the state housed 9.8 million hogs. In 1997, the poultry industry consisted of approximately 60 million turkeys and 680 million chickens.[16] In 1995 a toxic outbreak of Pfiesteria occurred in North Carolina after five major spills from lagoons of hog waste released an estimated 30 million gallons of nutrient-rich waste into the Neuse River in North Carolina[17].

And in Maryland, approximately 620 million chickens are raised on the eastern shore of the Chesapeake Bay each year.[18] In the Pokomoke River watershed in Maryland, the amount of chicken manure spread on fields as fertilizer every year equals the sewage output of a city of 1 million people.[19]

There is some scientific support for the hypothesis that North Carolina’s fish kills have been more significant (numbering in the billions rather than the thousands or millions, as in Maryland) because the Chesapeake Bay is deeper than the Albemarle-Pamlico Estuary system, and more frequently and thoroughly flushed by the ocean as a result of its wider opening to the Atlantic. The greater depth may reduce the growth of phytoplankton that feed Pfiesteria, and may make the Bay waters less calm.[20]

In addition, the Outer Banks, a system of barrier islands along the North Carolina coast, prevents the flushing out of the nutrients and pollutants from inland waters that contribute to the conditions under which Pfiesteria thrives.

While Pfiesteria seems to be present in some form all along the coastal estuaries of the Atlantic, it is not always actively causing fish kills. Certain conditions need to be present before the dinoflagellate begins to emit toxins that kill fish and affect humans. The ideal conditions include a combination of brackish waters, high concentrations of phytoplankton that feed Pfiesteria, and large schools of fish that trigger toxin production by Pfiesteria.

What Does It Do?

Unlike some other toxic dinoflagellates, Pfiesteria does not accumulate in the food chain, harming fish and humans who ingest it.[21] Nor does it seem to proliferate and suffocate fish by building up in gills.

Instead, Pfiesteria responds to the trigger of large numbers of fish by releasing toxins that stun the fish, lower their immune resistance and damage the fish skin. The fish die in large numbers.[22] Pfiesteria, in some of its forms, feeds on the dead and dying fish in a process called myzocytosis, in which zoospores, gametes and planozygotes attach with an extended peduncle and suction the interior cytoplasm and organelles.[23]

In addition, Pfiesteria toxins can harm people. People who are exposed to the toxin on their skin or who inhale the toxin in aerosolized form can be beset by severe neurological deficits that fade, more or less, with time and the end of the exposure. Symptoms have ranged from narcosis, eye irritation, respiratory distress, stomach cramping and vomiting, epidermal lesions, cognitive impairment, fits of rage and short-term memory loss.[24] There is some indication that immune responses may be hampered, in both humans and in fish.[25]

Fish health

Pfiesteria responds to unidentified fish excreta by swimming toward fish prey and emitting multiple toxins.[26] The toxins are as yet unidentified, except that one is water-soluble and one is fat-soluble.[27] The toxins narcotize the fish, causing erratic swimming patterns and distress, bleeding, difficulty obtaining sufficient oxygen and extensive lesions and death.[28] The fishes’ epidermal tissue and osmo-regulatory functions are destroyed or severely impaired.[29]

Pfiesteria toxins also can make the fish vulnerable to disease-causing bacteria and fungi.[30] Finally, as noted above, various stages of Pfiesteria feed on the cells of the dead and dying fish. Within hours of a toxic outbreak, following the death of most of the fish, Pfiesteria’s toxic stages transform into non-toxic forms.[31]

Recent tests also indicate that fish exposed to low concentrations of toxic Pfiesteria suffered from white blood cell counts 20 to 40 percent lower than normal, suggesting that Pfiesteria toxins may compromise the functioning of the immune system. Eggs of striped bass and other fish fail to hatch, shellfish larvae are killed and young bay scallops lose the ability to fully close their shells.[32]

Human health

Pfiesteria and its MRO’s cause Estuary Associated Syndrome in humans. Lab workers with heavy exposure, watermen and a waterskier are some of the victims of the syndrome. The most common symptoms of EAS are lack of concentration, forgetfulness, inability to learn new information, information overload, skin lesions or burning sensations and possible immune impairment.[33]

Unlike other toxic dinoflagellates, Pfiesteria does not appear to build up in seafood and harm people who eat the seafood. People get ill who get toxin-laden water on their skin or who breathe aerosolized toxins in the air over the areas where fish are hurt or dying from Pfiesteria.

Studies of watermen exposed to Pfiesteria bore out the symptoms reported by the three lab workers who were exposed to water containing Pfiesteria toxin by skin and aerosol contact in a lab setting.[34] Neuropsychologic testing showed severe memory impairment, including recall for verbal and visual information, and abnormal attention spans.[35] Suggestions that Pfiesteria EAS complaints were psychosomatic have been rejected.[36]

In addition, studies conducted in which rats were exposed to Pfiesteria toxins showed significant deficits in their ability to learn new mazes, which were more pronounced when the tests were conducted in a chamber without sound attenuation, indicating susceptibility to distraction.[37]

What Is Being Done?

Due to the increase in the number of HAB’s, there is considerable political activity that attempts to reduce nutrient runoff from agricultural facilities like hog feed-lots and chicken farms. The problems to be addressed include non-point source run-off of fertilizer and waste, and spills from waste lagoons. Increased protection for wetlands and limits to farming in floodplains are two strategies being used. Some activity centers on the state level, some on the federal level.

In North Carolina, state regulators proposed a plan in 1996 to reduce by 30 percent the amount of nitrogen runoff in various land use zones. Some combination of riparian buffers, nutrient management, drainage or other best management practices were proposed to reduce the nutrient load from farmland.[38] A moratorium on new hog farms was put in place the year after massive swine waste lagoon spills into the Neuse River. Farmers in North Carolina protested, as did commercial fishers.[39]

In Maryland, the governor appointed a panel to assess the dangers. The panel strongly urged reductions in the use of manure as fertilizer, and the Maryland Assembly considered bills to accomplish that reduction. Farmers found such proposals “alarming” and organized to oppose them, in vain.[40]

Other Atlantic coast states, including Virginia, Delaware, West Virginia, Pennsylvania, South Carolina and Florida, are cooperating in research and data-sharing, and several are setting up task forces and research units.[41]

Considerable amounts of grant monies are being funneled into Pfiesteria research, including more that $2.4 million in state and federal funds from the Maryland and from the National Oceanic and Atmospheric Administration.[42]

Federally, the EPA announced a proposed strategy to cope with the problem of agricultural runoff from non-point sources, including permitting under the Federal Water Pollution Control Act. The system of TMDL’s instituted by the states under the Section 303(g) of the FWPCA has been criticized for being poorly designed, monitored and enforced. Other federal statutes with potential impact include the 1987 Water Quality Act, section 319 (providing grants to states to develop non-point source management programs, but not requiring implementation of enforceable laws) and the 1990 Coastal Zone Management Act (each coastal state required to develop a non-point source pollution control program).[43]

In 1999, Congress passed 16 U.S.C. section 1451, the “Harmful Algal Bloom and Hypoxia Research and Control Act of 1998,” providing funding for research on HAB’s, which was referred to the Senate Committee on Commerce, Science and Transportation and heard from no more. Congress also passed H.R. 2565, the “Pfiesteria Research Act of 1997,” which appears to have died in a different committee in the Senate. Meanwhile the Senate passed a bill called “The Atlantic Coast Toxic Microorganism Environmental Remediation Act,” which was also referred to the Committee on Environment and Public Works. In 1998, the House referred a bill entitled the “Farm Sustainability and Animal Feedlot Enforcement Act” to the Committee on Transportation and Infrastructure.

The many federal agencies whose program areas cover HAB’s, including the EPA, the National Science Foundation, the Department of Health and Human Services’ National Institute of Health, the Department of Defense’s Office of Naval Research, NASA’s Office of Earth Science, and the Department of Commerce’s National Oceanic and Atmospheric Administration, are trying to jointly fund research.

Research is continuing on all aspects of Pfiesteria and its MRO’s, including human health effects, toxin identification,[44] effective methods of identifying Pfiesteria-laden areas at risk through gene probes and toxic bioassays and possible control methods.[45] Research is continuing on all aspects of Pfiesteria and its MRO’s, including human health effects, toxin identification, effective methods of identifying Pfiesteria-laden areas at risk through gene probes and toxic bioassays and possible control methods.

Long Term Implications

The main concerns to scientists studying Pfiesteria are the potential threat to viability of fish populations, human health concerns, and the possible economic effects on tourism, fisheries and recreation. Estuaries are the nursery ground for a wide variety of fish species. If fish kills weaken immunity and reduce breeding populations, it could affect the ability of fish populations to recover.

Dr. Burkholder believes that HAB’s are clear evidence of the increasing stresses on estuarine ecosystems from anthropogenic effects. She likens fish killed by MRO’s to canaries in a coal mine, an early warning system that we would be foolish to ignore.

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[1] Newsday, NY, October 7, 1997, p.C3, quoting Dr. JoAnn Burkholder.

[2] “The Lurking Perils of Pfiesteria”, Scientific American, August 1999, pp. 42-49, Burkholder, J.M.

[3] Ibid.

[4] “Fish lesions in the Chesapeake Bay:Pfiesteria-like dinoflagellates and other etiologies”, Maryland Medical Journal, 47 (3), pp. 106-112, Kane, A.S., Oldach, D., and Reimschuessel, R.

[5] NCSU Aquatic Botany Laboratory Pfiesteria piscicida Page

 

[pic]

[6] Ibid., fn.3.

[7] Pp can survive a bath in concentrated sulfuric acid or ammonium hydroxide, thirty-five days of dessication, or almost two years of dormancy. Watch out for killer algae, E–the Environmental Magazine, V. 7, Mar/Apr 1996, pp. 15-19, Mulvaney, K.

[8] And the Waters Turned to Blood, by Rodney Barker, Simon & Schuster 1997

[9] Ibid., fn.4.

[10] Congressional Research Service Report for Congress: “Pfiesteria and Related Harmful Blooms: Natural Resource and Human Health Concerns”, 12/8/97, Buck, E.H., Copeland, C., Zinn, J.A., and Vogt, D.U.

[11] A study of the relationship between inorganic and organic nitrogen and the growth of dinoflagellates in eutrophic conditions found a striking relationship between the availability and uptake of urea and the outbreak of dinoflagellates. In 25 sampling periods in estuarine ponds with temperatures between 5 and 30 degrees Centigrade, urea concentrations greater than 1.5 uM co-occurred with dinoflagellates 75 percent of the time. Abstract of a report to conference in Santa Fe, Feb. 1999, Gilbert, P.M., Terlizzi, D.M., Lomas, M.W., Fan, C.

[12] “Pfiesteria piscicida and other Pfiesteria-like dinoflagellates: Behavior, impacts and environmental controls”, Limnology and Oceanography, 42(5, part 2), 1997, p. 1052-1075, Burkholder, J.M. and Glasgow, H.B., Jr.

[13] Baltimore Sun, Jan. 31, 1998, p. 1B

[14] Fort Lauderdale Sun-Sentinel, March 19, 1998, p. 1A

[15] In the Neuse and Cape Fear River Basins of North Carolina, in the 1980’s 2 million livestock head were counted in 21,000 operations, and 15 years later the number reached 8.3 million head in 6000 operations. This speaks to not just growth but also to concentration. “Coastal management”, Water - Environment and Technology, v. 9, Aug. 1997, pp. 63-65, Doll, B.

[16] Comparative effects of poultry and swine waste lagoon spills on the quality of receiving streamwaters, Journal of Environmental Quality, v. 26 Nov./Dec. 1997, pp. 1622-31, Mallin, M.A., Burkholder, J.M., McIver, M.R.

[17] “Impacts to a coastal river and estuary from rupture of a large swine waste holding lagoon,” Journal of Environmental Quality, v. 26, Nov./Dec. 1997, pp. 1451-66, Burkholder, J.M., Mallin, M.A., Glasgow, H.B., Jr.

[18] “Cell from Hell”, Sierra Magazine, 84 (1), Jan./Feb. 1999, p. 34, Guynup, S.

[19] St. Louis Post-Dispatch, September 22, 1997, p. 1A.

[20] The Baltimore Sun, August 29, 1997, p. 17A.

[21] Blooms of the Alexandrium species of dinoflagellates cause shellfish to become toxic. People who eat shellfish that carry saxitoxins can suffer paralytic shellfish poisoning (PSP), which can lead to respiratory paralysis. Ciguatera is another species that can lead to poisoning of humans who eat affected fish, bringing episodes of gastroenteritis and neurological symptoms. Red tides of Gymnodinium breve along the Florida coast have caused deaths to seabirds and marine mammals like the manatee. G. breve can also cause respiratory and eye irritations in humans who are exposed to it in sea spray, its aerosolized form. Two other kinds of poisoning by fish consumption, diarrhetic and amnesic shellfish poisoning, are also the result of the toxins carried by fish who eat harmful algae. “Pfiesteria, ‘The Cell from Hell,’ and Other Toxic Algal Nightmares,” Clinical Infectious Diseases 1999; v. 28, pp. 1191-1198, Morris, J.G., Jr.

[22] “In 1991, we lost over a billion fish. They were burying them on the beach with a bulldozer. And in 1995 we lost well over ten million.” Rick Dove, Riverkeeper for the Neuse River in North Carolina, quoted in “Cell from Hell,” Sierra Magazine, ibid. fn. 18.

[23] Ibid., fn.12.

[24] Ibid., fn.12.

[25] Ibid., fn.2.

[26] Ibid., fn.12.

[27] “Strategies for environmental monitoring of toxin producing phantom dinoflagellates in the Chesapeake,” Maryland Medical Journal, May 1998, 47(3), p. 113-119.

[28] “A new ichthyotoxic dinoflagellate: cause of acute mortality in aquarium fishes,” The Veterinary Record (1993), v. 133, p. 96-97, Noga, E.J., Smith, S.A., Burkholder, J.M., Hobbs, C., Bullis, R.A.

[29] Ibid., fn.12.

[30] In particular, the fungus Aphanomyces can cause lesions and die-offs of fish. The question of whether Pp or Aphanomyces causes the extensive lesions commonly associated with Pp outbreaks appears to be somewhat contested. “Fungus, not Pfiesteria, blamed for fish lesions,” Environmental News Network, October 6, 1998. And ibid., fn.4.

[31] Ibid., fn. 27.

[32] Ibid., fn.2.

[33] For hair-raising descriptions of the human health effects, see And the Waters Turned to Blood, ibid. fn.8, for its discussions of JoAnn Burkholder and Howard Glasgow’s bouts of EAS. Dr. Burkholder has had pneumonia 16 times since she had Pp-caused EAS, in 1995.

[34] “Learning and memory difficulties after environmental exposure to waterways containing toxin-producing Pfiesteria or Pfiesteria-like dinoflagellates,” The Lancet, August 15, 1998, v. 352, p. 532-538, Grattan, L.M., Oldach, D., Perl, T.M., Lowitt, M.H., Matuszak, D.L., Dickson, C., Parrott, C., Shoemaker, R.C., Kauffman, C.L., Wasserman, M.P., Hebel, J.R., Charache, P., Morris, J.G., Jr.

[35] “Neurologic symptoms following Pfiesteria exposure: case report and literature review,” Maryland Medical Journal, May 1998, 47(3), p.120-123, Bever, C.T., Jr., Grattan, L.M., Morris, J.G.

[36] “A critical review of the Pfiesteria hysteria hypothesis,” Maryland Medical Journal, May 1998, 47(3), p. 133-136, Greenberg, D.R., Tracy, J.K., Grattan, L.M.

[37] “Persisting learning deficits in rats after exposure to Pfiesteria piscicida,” Environmental Health Perspectives, v. 105 (1997), p. 1320-1325, Levin, E.D., Schmechel, D.E., Burkholder, J.M., Glasgow, H.B., Jr., Deamer-Melia, N., Moser, V.C., Harry, J.G. And “Pfiesteria Toxin and Learning Performance,” Neurotoxicology and Teratology, 21(3), p. 215-221 (1999), Levin, E.D., Simon, B.B., Schmechel, D.E., Glasgow, H.B., Jr., Deamer-Melia, N.J., Burkholder, J.M., Moser, V.C., Jensen, K., Harry, G.J.

[38] Ibid., fn.14.

[39] “The water will take care of itself,” quoting a fisherman in Pamlico County, North Carolina. The Boston Globe, November 30, 1998.

[40] The Baltimore Sun, January 4, 1998, p.1B.

[41] Ibid., fn.10.

[42] The Baltimore Sun, October 6, 1998, p.2B.

[43] “Reinventing Environmental Regulation: Back to the Past by Way of the Future,” Environmental Law Reporter, July 1998, v. 28, p. 10361-10372, Steinzor, R.I.

[44] The Baltimore Sun, October 6, 1997, p.1A.

[45] “Response of two zooplankton grazers to an ichthyotoxic estuarine dinoflagellate,” Journal of Plankton Research (1995), 17(2), p. 351-363, Mallin, M.A., Burkholder, J.M., Larsen, L.M., Glasgow, H.B., Jr.

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