Toxic water events
usually linked with some form of harmful algae bloom have been reported by researchers
and the media with increasing frequency since the 1970's. There have been reports
of red tides, brown tides, people becoming seriously ill or dying after eating
fish or mussels, manatees found dead by the dozens, a whole herd of cattle dying
after drinking from a pond, and most recently, an outbreak in ChesapeakeBay of
a potent water toxin that has killed thousands of menhaden and has reportedly
caused ill effects to fishermen and others working on the water. Speculation on
the cause of this most recent outbreak of the organism Pfiesteria piscicida
has prompted congressional hearings and funding of millions of dollars for research
to several government agencies.
Most scientists are in agreement that there does seem to be some evidence of increasing frequency of toxic water events; however, there is no consensus on either the causes or what can be done to reduce the future risk. Some theories postulate that these events are evidence of rising pollution or alteration of thenutrient ratios of our coastal waters by sewage pollution and agricultural runoff. Other theories center on climate changes, ballast water transfer of organisms, or any of a myriad of possibilities, including that we are not experiencing more toxic events, but instead are simply more aware and better able to iden-tify the water toxins. Scientists tell us the an-cient microscopic single-celled aquatic organ-isms believed to be responsible for these recent events have in all probability been causing toxic outbreaks since the beginning of time.
To further complicate the issue, harmful algae blooms occur in all types of water-- from crystal clear to highly polluted. Even when marine scientists are able to obtain a water sample containing a toxin, identification of the tiny microscopic organisms is still required and is not always possible. As an example, the Pfiesteria organism was only identified as recently as 1992. To date there are still only a handful of people in the world able to identify this deadly organism that has just this year made its presence known in Chesapeake Bay. Thus far no one can detect its toxins chemically--bioassays are the only tool.
In this issue we will touch on the most common types of water toxins, symptoms they cause, and theories for the seeming proliferation of toxic events.
Chicken farmers along the Chesapeake and neighboring tributaries have been
the subject of heated debate in the state of Maryland after the recent Pfiesteria
outbreak. Chicken manure, which is naturally rich in nitrogen and phosphorus,
is routinely spread on cropfields as a fertilizer. There has been much speculation
that the consequent agricultural runoff may be a factor in spurring the
microbe to a toxic level. However, no scientific studies of the Chesapeake
Pfiesteria have confirmed this theory.
Adding to this quandary is the increasing ambiguity of the point vs nonpoint source pollution discharge issue. The Environmental Protection Agency has traditionally defined point source pollution discharge as pollutants that come from areas such as factories, mills, sewage treatment plants, and storm sewer outfall, while nonpoint sources were categorized as pollutants emanating from rainwater runoff from construction sites, farming areas, suburban areas, or cities. The latter categories, being of considerably broader scope, had been considered beyond citizen lawsuits. The recent Southview Farm case has considerably muddied this traditional schism of the two types of pollution discharge. In Southview, a dairy farm's practices of manure spreading was found by the Second District Court of Appeals to constitute point source pollution and thus to be in violation of the Clean Water Act. In 1995, the U.S. Supreme Court allowed the ruling to stand, and the specter of point sourcing of agricultural and other traditional nonpoint sources has made this environmental issue quite vexing. Consequently, the existing legislative and regulatory mechanism for treating nonpoint sources is being looked at anew. For discussion of the agricultural runoff issue, see Concerned Area Residents for the Environment vs Southview Farm, 34 F.3rd 114 )2nd Cir., 1994), cert demied, 115 S Ct. 1793 (1995). |
Of the thousands of species of dinoflagellates, com-monly referred to as algae that form a significant part of primary planktonic production in both oceans and lakes, only a few produce potent toxins that can cause harmful effects to water creatures and humans. The single-celled dinoflagellates are major players in most of the toxic water events designated as "red tides" or harmful algal blooms (HABs). Both heterotrophic (eat other organisms) and autotrophic (photosynthetic) dinoflagellates are known. Some are both. The life cycle of the dinoflagellates is moderately complex and can involve several stages, both sexual and asexual, motile and non-motile.
Different species of dinoflagellates produce different toxins and for clarity they are classed according to the symptoms they produce. The poisoning syndromes caused by dinoflagellates have been given the names paralytic, diarrhetic, and neurotoxic shellfish poisoning or PSP, DSP and NSP. Humans are affected after consuming shellfish such as clams, mussels, oysters or scallops or fish that have been feeding on shellfish that contain the toxins. Ciguatera toxins, produced by another dinoflagellate, are transferred through the food chain by reef fish that have been feeding on the harmful algae toxins attached to surfaces in coral reef areas. Impossible to detect with the naked eye, this highly potent toxin may affect human consumers and other marine life as its toxin is biomagnified through the food chain. For centuries caribbean islanders have avoided eating certain fish for fear of ciguatera long before there was any knowledge of its deadly dinoflagellate connection.
Amnesic shellfish poisoning (ASP) is caused by yet another single-celled aquatic organism-- a diatom. Diatoms are different from dinoflagellates in that they do not have flagella, and they tumble around in the water protected by a thick coat of silica. However, in 1987, 3 people died and over 100 became ill from eating clams containing domoic acid produced by tiny diatoms. This toxin has been detected on the East, West and Gulf coasts of the United States. Yet another algal group is the cyanobacteria, a deadly form of blue green algae in fresh water lakes and ponds that is responsible for many cattle and livestock deaths each year.
The dinoflagellate Pfiesteria piscicida has thus far not been shown to produce any symptoms when affected fish are consumed by humans; instead the toxin seems to affect small fish like menhaden and can literally eat them alive. It has been speculated the few reports of human illness have been from direct contact with water or aerosols containing the Pfiesteria toxin.
Scientists have learned to identify many of the toxic organisms and the symptoms they produce in human and wildlife populations. However, what causes outbreaks of the toxic blooms is less well understood. For this reason scientists knowledgeable in the area of water toxins urge caution against pointing accusing fingers too hastily, such as has already occured in the recent Chesapeake Bay Pfiesteria outbreak. In written testimony before a congressional subcommittee September 27, agricultural runoff was cited as a major culprit in the Pfiesteria event by altering the levels of nitrogen and phosphorous levels in the Chesapeake. Although some studies have shown some of the microorganisms respond to changes in nutrient levels, the complexities of natural interactions prevent any simplistic assessment. Other studies show the levels of nitrogen and phosphorous have little bearing on water toxin proliferation from other species.
| Biotoxin | Biotoxin Name | Microorganism | Route of Exposure | Some Possible Symptoms |
 |
Ciguatera | dinoflagellate Gambierdiscus toxicus | eating contaminated fish such as grouper, snapper, amberjack and barracuda in the "reef" food chain | abdominal pain, diarrhea, nausea, vomiting, muscle aches, dizziness, numbness, paralysis, anxiety, chills, bradycardia, tachycardia, sweating, long lasting fatigue & in rare instances coma or death |
| Neurotoxic Shellfish Poisoning (NSP) | dinoflagellate Gymnodinium breve "Red Tide" | eating contaminated shellfish or coming in contact with aerosols of G. Breve | muscle aches, tingling & numbness of the lips, tongue & digits, diarrhea, abdominal pain, dizziness, anxiety & sweating, muscular paralysis or respiratory difficulties, eye irritation- a non-fatal human syndrome. | |
 |
Paralytic Shellfish Poisoning (PSP) | dinoflagellate Gonyaulax tamarensis & G. cantenella | eating bivalves such as mussels, clams, or scallops exposed to contaminated waters | drowsiness, incoherence, fever, rash, tingling and numbness of lips, burning of the perioral area, dry throat & dry skin, in severe cases respiratory failure and death. |
 |
Chesapeake & North Carolina fish kills | dinoflagellate Pfiesteria piscicida | coming in contact with the water containing the microbe not from ingestion of contaminated fish | narcosis, respiratory distress with asthma like symptoms, stomach cramps, nausea, vomiting, eye irritation, sweating, tachycardia, fatigue |
| Amnesic Shellfish Poisoning (ASP) | diatom Pseudonitzschia sp . | eating toxic shellfish | nausea, vomiting, abdominal cramps, diarrhea, dizziness, headache, seizures, disorientation, permanent memory loss, respiratory difficulty, coma and death |
Other research theories point to complex interactions of climate, ocean and temperature affecting marine plankton and other organisms. Toxic species may be introduced by increased ocean shipping. Microorganisms lurking in bilge water or ballast can be transported thousands of miles to take up residence in a whole new watery world. Introduction of new aquaculture such as shellfish or fish farms can reveal the presence of harmful algaes in places that had formerly exhibited no signs of water toxins. Increased regulation and scientific scrutiny is also revealing toxins that may have always been present. Whatever the cause of the toxic events in salt water and freshwater bodies of water, the call for caution against joining the tide of panic and popular opinion and relying instead on reasoned science may be our best hope for understanding and reducing toxic water events.
 |
Special thanks to Dr. Donald Anderson for his help in preparation and editing of our newsletter. Dr. Anderson is Senior Scientist in the Biology Department at Woods Hole Oceanographic Institute in Woods Hole, MA. Dr. Anderson also directs the National Office for Marine Biotoxins and Harmful Algaes. |  |
On October 18, 1997
Vice President Gore announced a set of clean water initiatives to celebrate the
25th anniversary of the CLEAN WATER ACT. The USDA and the EPA were directed
to develop a comprehensive plan within 120 days to strengthen and improve water
pollution control efforts. Of particular note is the EPA directive to "identify
major sources of nitrogen and phosphorous in our waters and identify actions to
address these sources." The V.P. declared that "EPA will expedite its new strategy
from animal feeding operations that produce polluted runoff, and include in that
strategy specific commitments to revise outdated regulations. The complete notice
was published in the November 7, 1997 Federal Register. Comments about
the Vice President's proposals must be received by December 8, 1997.
The Society for Risk Analysis will hold its annual meeting and exhibition in Washington, DC, December 7-10. One of the workshops is entitled: The Risks of Communicating on Environmental Risk...It's the Communication Itself That Can Be Most Risky.
For more information on harmful algaes: www.redtide.whoi.edu/hab
A number of our
readers have asked us about the smiling face that greets them on this page. He
is known as the Nuremberg skeleton, dating from 1493, a significant historical
symbol of information advancing forward the medical profession. Anatomical renderings
of the human skeleton had been done very piecemeal prior to the end of the 15th
century, probably because of the skeleton's dualistic function as a symbol of
death to the medieval mind. Physicians seemed wary of using the skeleton as a
teaching tool in that it was also used as a memento mori (symbol of death) The
skull, in particular, was seen as a reminder of death, from the Latin phrase meaning
"remember you must die" And it is to the genius of the artist that he gave the
skull an innocent and beguiling smile. The effect was to provide a means of using
human anatomy in a non-threatening manner to advance understanding of the medical
arts. As such, he seems an appropriate icon at MTI for the medical and scientific
information we provide our clients.
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