Red Tides Ment Quoted on the Cover Page of 1976 a Red Tide Off the Coast of Describing the First of the Ten Plagues New Jersey Caused Extensive Mor Alan W

The passage from the Old Testa west coast of Florida. In the summer Red Tides ment quoted on the cover page of 1976 a red tide off the coast of describing the first of the ten plagues New Jersey caused extensive mor Alan W. White of Egypt may very well represent talities of marine animals, and nearly one of the earliest recorded in 70 per cent of the surf clam (bar Fisheries and Environmental stances of a red tide. Red tides are clam) population was killed. How Sciences not uncommon in that part of the ever, the consequences for humans Department of Fisheries world. In fact, the Red Sea is so can also be serious. In northeastern and Oceans named because of red tides which Venezuela in 1977, red tides Biological Station, occur there. Red tides have probably poisoned shellfish and caused 193 St. Andrews N.B., EOG 2XO existed on earth ever since the ap cases of human illness, ten of which pearance of the causative microor were fatal. ganisms hundreds of millions of In recent years it seems there has years ago. been an increasing number of re The consequences of red tides are ports of red tides throught the world. often dramatic and severe. As They have been recorded in Argen sociated with many of these out tina, Brazil , Canada, Chile, England, breaks are mass mortalities of all Japan , the Netherlands, Norway, sorts of marine animals and con Papua New Guinea, Peru, Scotland, tamination of shellfish with potent Spain, United States and Venezuela. neurotoxins which can prove fatal to Considering the importance of red humans and other shellfish consum tides to fisheries resources and ers. human health, let's explore the na Red tides have significant and ture of red tides, why they occur, far-reaching economic impact. This how they kill and contaminate ani results from outright losses of fish mals, and what is being done about and shellfish resources, from them. shellfish harvesting restrictions, from consumer wariness of seafood pro ducts in general (even though largely unfounded), and from decline in tourism. Frequent and devastating red tides constitute a major problem for coastal fisheries in Japan, and fishing, of course, is a mainstay in that country's economy. On the east and west coasts of Canada closures of shellfish areas to harvesting , be cause of the danger of red-tide toxin to public health , results in a potential loss to fisheries of millions of dollars annually. The negative effect of red tides on tourism is also significant. The 1973-74 red tide in Florida was estimated to have caused $15 mill ion loss to the tourist industry alone! One can only guess at the overall adverse effects of red tides and their publicity on sales of seafood pro ducts, but they are probably consid erable in many instances. Fish and shellfish are among the animals that generally fare the worst during red tide episodes. For exam ple, it has been estimated that close to a half billion fish were killed as a result of the 1947 red tide on the Co. .Jno <002 I

Underwater World 3

A brief summary of aquatic food of the most important processes on What are red tides? chain events is helpful for an under earth, because it serves as the first standing of red tides . The lighted, step in the system of energy trpnsfer surface layers of the world's water through aquatic food webs. All the bodies, both freshwater and marine, animals of fresh and salt water de contain large numbers and varieties rive their sustenance, ultimately, of microscopic, single-cell plants cal from these small plants. led algae. These tiny aquatic plants These microscopic algae, which capture and utilize energy from sun occur in a vast variety, generally go light, just as do land plants. The through yearly cycles of rapid growth growth of these aquatic algae is one and decay. The growth period is characterized by a burst of growth and multiplication for two or three (';·· weeks, during which time each single plant may have multiplied into mill ions of its kind. This phenomenon is called blooming, and it goes on season after season in surface wat ers all over the world . Which particu lar microscopic plants grow in any Gulf o f given water body depends upon a St. Lawrence number of factors, the major ones being temperature , salinity, light in Magdalen /Is. tensity, and nutrient level. (, Co bo l Thousands of different species of microalgae exist, periodically bloom ing and decaying. They are the in itiators of the food chain . In certain instances hydrographic and meteorological events cause the microalgae in a bloom covering a wide area to be concentrated into one or several smaller areas so that very dense accumulations of the organisms occur, with up to millions of algal cells per litre. In such large numbers, the algae discolour the water. The colour is due to pigments

_: Ess ex within the algae which are used for :. Bea c h trapping sunlight. Different algae

66° have different pigments, thus diffe rent colours. Therefore, depending " The locations (hatched) of toxic blooms upon the specific algae involved, and paralytic shellfish poisoning (PSP) discolouration of the water may be on the Canadian Atlantic coast (from shades of red, pink, violet, orange, Prakashetal. 1971). " yellow, blue, green , or brown. How ever, many of the discolourations due to algae in marine waters are red, hence the terms "red tide" or "red water" . The terms are as sociated with the phenomenon itself, so the colour of a "red tide" is not necessarily red , but may be any other colour. For some reason, the phenomenon in fresh water is not referred to as a " red tide ," but as a "water bloom". 4 Underwater World

What causes this concentration of upwards. This is the mechanism by How do red tides occur? algae into one location to form a red which tremendous numbers of algae tide? A combination of biological, from a large area can be accumu hydrographic, and meteorological lated into one spot. Of course, water processes explains how this occurs. currents play an important role in Most red tides algae are either free transporting algae to these potential floating or are positively phototactic, red tide areas and in supplying the which means they actively swim to nutrients required to maintain growth wards light (small whiplike tails ena of the algae. Depending upon con ble them to do this) . Once at the tinuation of the proper hydrographic surface, the organisms can be con condition and upon a supply of nut centrated into areas where the water rients, a red tide may persist in one is "downwelling" or sinking. This location for a week or two, often occurs where two water masses causing extensive mortalities of meet, or where thermal or wind marine animals, especially fish and driven convection patterns (win shellfish , and sometimes con dows) exist. In short, the water is taminating shellfish to the extent that moving downwards while the or the lives of those organisms eating ganisms are floating or swimming the shellfish are endangered.

Mass mortalities of marine or effective as poisons to warm How do red tides kill ganisms result from red tides for two blooded animals. marine animals and con reasons. The first involves oxygen The west coast of Florida is noted depletion when red tide-causing mi for its frequent and extensive fish taminate shellfish? croalgae die. Lack of nutrients or kills caused by red tides. The causa unfavourable conditions of light, tive organism there, Gymnodinium temperature, or salinity can cause breve , produces a toxin which the entire population of red tide causes red blood cells to burst. The organisms to die simultaneously. organism is so fragile that it is bro The subsequent degeneration (rot ken open , releasing its toxin , when it ting) of these numerous microor passes through a fish 's gills. The fish ganisms can cause oxygen deple then absorbs the toxin through its tion of the surrounding waters. Few gills. The fish dies of asphyxiation animals can withstand prolonged because the toxin bursts its red oxygen depletion, and mass mor blood cells , upon which the fish talities result. The 1977 red tide depends for oxygen uptake. A vivid catastrophe off New Jersey is a good description of such a kill is given by example. In this case an oxygen S.T. Walker in 1884 (Proc. U.S. Nat. deficient area of over 14,000 square Mus. 6: 105): km occurred, causing mass mor " On leaving Clear Water , talities of marine animals, especially November 20, I sailed south of bottom forms , like surf clams , through Boca Ciega Bay and en which could not escape. countered the first dead fish float The second reason is more intrigu ing on the water near Bird Key, a ing and relates to the fact that many little southeast of Pass A'Trilla. red tide algae produce toxins. Little These were mullet, and as we is known about why and how these progressed to the south and east I algae synthesize toxic substances, began to encounter toadfish, eels, but the toxins they produce are puff-fish and cow-fish , in immense among the most potent natural numbers ... I saw many fish in poisons in the world. Different toxins every stage of sickness, from the are produced by different algae. first attack to the end. All were Some toxins are effective fish affected in nearly the same man poisons while others, which are ac ner. The fish , apparently active cumulated by shellfish, seem most and healthy, would be swimming along, when suddenly it would turn Underwater World 5

on its sides and shoot up to the top of the water, gasping as though out of the water, apparently unabre to control its motions, often lying on its side on the bottom for five or ten minutes motionless, then sud denly shooting hither and thither without aim or object, and finally ending the struggle on the surface and floating off dead. Whole schools of mullet would suddenly stand upright on their tails, spout ing water and die in five minutes. Gars would run for a long time with their snouts above the water, and then lie motionless, as if dead, for ten or fifteen minutes. These gen erally lived an hour or more after being attacked." Similar fish-killing red tides of toxic microalgae also occur occasionally along the coasts of England. Red tides of the Florida organism are also noted for causing trouble some respiratory irritation among humans when winds blow spray from red tide areas ashore. It is not known if the irritation is due to the same compound that causes the problem for fish. But this, together with piles of dead fish washed up along the shores, accounts for the decrease in tourist trade. There is another group of toxin producing red tide microalgae which is responsible for the phenomenon " paralytic shellfish poisoning " (PSP) . This is the Gonyautax gro11p It is represented-"by several toxic species occurring in a number of locations throughout the world. "A photomicrograph of the toxic red These microalgae produce an ex tide microorganism, Gonyaulax ex cavata, responsible for paralytic tremely potent toxfh which inhibits shellfish poisoning in eastern Canada the transmission of nerve impuTSeS_. and New England. The organisms are reading to muscular paralysis and about 0.03 millimeters across. A " dup eventual death by asphyxiation. let" is just finishing the process of cell Warm-blooded animals are particu division." larly sensitive to the toxin, and some cold-blooded an imals (fish and inver tebrates) are also affected. Curi ously, many filter-feeding shellfish (clams and mussels, for example) are not sensitive to the toxin . In fact, the shellfish are content to feed upon the red tide organisms and , in the process, they store and accumulate the toxin in their digestive glands. 6 Underwater World

Here lies the problem, because America, along the coasts of north the shellfish can store great quan western Europe and the United tities of toxin (with little or no effects) Kingdom , and around Japan. and thus become extremely danger Canada experiences some of the ous if eaten by toxin-sensitive ani most regular and severe outbreaks mals. This explains the name paraly - along the coast of British Colum tic shellfish poisoning (PSP). In ex bia , in the southern Bay of Fundy, treme cases, just several clams or and in the St. Lawrence River es mussels may prove fatal if eaten by a tuary. The culprit on the east coast is human. Such intoxication of shellfish Gonyaulax excavata and on the west is an insidious problem because al coast its relatives,~ and though it is occasionally associated G. acatene/la. Although bona fide with large and obvious kills of marine ..red tides occur along the west coast, animals, th is is often not the case. the pronounced turbulence on the Contaminated shellfish appear nor Canadian east coast usually pre mal, so there is no indication of the cludes red tide formation. Despite potential danger. this, annual dense blooms of G. Instances of PSP have been re excavata cause high toxicity levels corded from numerous locations in shellfish nearly every summer, throughout the world. Most PSP out necessitating closure of many areas breaks have occurred along the west to shellfish harvesting. and northeast coasts of North

Red tides are potentially catas has been adopted by other coun What is being done trophic natural events, much like tries. Weekly shellfish samples about red tides? earthquakes or hurricanes. They (clams and mussels mostly) are col have a long history and are largely lected and assayed for toxin, using part of nature's grand design. Even laboratory mice. If the toxicity ex though red tides may, perhaps, be ceeds a certain limit , beds in the stimulated by coastal pollution , area are posted and closed for har which may relate to the apparent, vesting. Continued sampling deter recent worldwide increase in red tide mines when the beds are safe to incidences , they are not solely a open. product of man 's alteration of coastal Present surveillance programs environments. This , together with could be improved, however, particu the fact that red tides occur so larly in the areas of sampling logis suddenly and randomly and over tics and toxin assay methods. De such large areas , means that spite the usefulness of the mouse schemes for red tide abatement and bioassay over the years, it has sev control by biological , chemical, or eral disadvantages. It is not very mechanical treatment are impracti sensitive, it requires considerable cal , at least at this stage of our time when samples must be sent to knowledge. At present, most efforts the testing facilities , and it requires on red tide problems focus either on the maintenance of large numbers of the applied aspects of surveillance mice. Efforts are now being made to and depuration or on the more basic develop a chemical assay for the aspects of general understanding toxin which will be rapid , inexpensive and prediction. and sensitive. Ideally, a chemical The danger of PSP to public health test would be made into a simple kit has necessitated the establishment so that commercial diggers or pic of shellfish surveillance programs in nickers could determine shellfish those countries which experience toxicity within minutes. fairly regular PSP outbreaks. Cana Following toxic red tides, shellfish da's shellfish toxicity monitoring may maintain their toxin loads for program , in existence since 1943, is various periods of time, from several one of the finest in the world , and weeks to several months, depending Underwater World 7

upon the oganism , the amount of Environment Canada Environnement Canada toxin stored and the time of year. I+ Depuration , or cleaning, of the toxin from these shellfish would enable them to be marketed. Shellfish depu ration plants for removing bacteria associated with sewage have existed for some time. Similar pro jects are being tested for depuration of red tide toxin . Although toxin contaminated shellfish wil l eventu ally depurate if maintained in red tide-free sea water, this may take too long to be economical. Recently, some success at reducing depura tion time has been achieved by exposing shellfish to ozone, which destroys the toxin . Experimental DANGER ozonation facilities have been estab lished in several areas. SHELLFISH AREA SECTEUR FERME Accurate predictions of red tide CLOSED A LA RECOLTE events and methods of inhibiting red DES MOLLUSQUES tide development depend upon a full understanding of the problem. Re CLAMS. MUSSELS AND OYSTERS LES CLAMS. LES MOULES ET search is now being conducted at IN THIS AREA, AS DESCRIBED LES HUiTRES DU SECTEUR DECRIT BELOW, ARE CONTAMINATED OR Cl·APRES SONT CONTAMINES OU laboratories throughout the world on CONTAIN PARALYTIC SHELLFISH CONTIENNENT UNE TOXINE exactly how and why red tides occur, POISON AND ARE NOT SAFE FOR PARAL YSANTE ET SONT IMPRO with the goal of developing methods USE AS FOOD. PRES A LA CONSOMMATION. of predicting red tide outbreaks well AREA DESCRIPTION: DESCRIPTION .OU SECTEUR: before they occur. We still have much to learn about the specific causes of red tides, for example, information about the factors that trigger their appearance. In addition , we need to know more about the THIS AREA IS CLOSED AND ANY CE SECTEUR EST FERME ET PERSON IN POSSESSION OF, OR TOUTE PERSONNE TROUVEE EN effects of red tides, especially ef FOUND TAKING CLAMS, MUSSELS POSSESSION DE CLAMS, DE MOUL· fects on the ecosystem itself. What OR OYSTERS FROM THIS AREA ES OU D'HUITRES, OU EN TRAIN ultimately becomes of red tide toxins IS SUBJECT TO PROSECUTION D'EN PRENDRE SERA POURSUIVIE in the marine environment? For in UNDER THE FISHERIES ACT. E~ VERTU DE LA LOI SUR LES Pi::CHERIES. stance, recei'tly shellfish toxins were implicated in a herring kill in the Bay MINISTER OF FISHERIES MINISTRE DES PECHES FOR CANADA of Fundy. Perhaps there are many DU CANADA other such unsuspected consequ "A sign posted to notify the public of ences of red tides for marine ani closure of a shellfish area because the mals. In summary, fish and shellfish shellfish contain paralytic toxins from resources , as well as public health, red-tide microorganisms." in many parts of the world are jeopardized by red tides, and al though interest and research efforts are increasing , a cure for this threat does not yet exist. Further Reading: Underwater World factsheets are Dale , B., and C.M. Yentsch . 1978. Red brief illustrated accounts of fisheries tide and paralytic shellfish poisoning. resources and marine phenomena Oceanus 21 : 41-49. prepared for public information and LoCicero, V.R., ed . 1975. Proceedings education. They describe the life of the first international conference on toxic dinoflagellate blooms. Mas history, geographic distribution, utili sachusetts Science and Technology zation and population status of fish , Foundation , Wakefield , Mass. 541 p. shellfish and other living marine re Mays, B. 1976. When the seas run red sources, and/or the nature, origin and the dinoflagellates bloom . and impact of marine processes and Oceans 9: 52-56 . phenomena. Prakash , A., J.C. Medcof, and A.O . Tennant. 1971 . Paralytic shellfish Text: poisoning in eastern Canada. Bull. Fish . Res . Board Can . 177 , 87 p. Alan W. White, Fisheries and En Quayle, D.B. 1969. Paralytic shellfish vironmental Sciences, Depart poisoning in British Columbia. Bull. ment of Fisheries and Oceans, Fish . Res . Board Can . 168 , 68 p. Biological Station , St. Andrews, Taylor, D.L. , and H.H. Seliger. 1979. New Brunswick, EOG 2XO Toxic dinoflagellate blooms. Proceed ings of the second international con Cover Photo: ference on toxic dinoflagellate blooms . Elsevier/ North Holland, New Part of a red tide caused by the York. 505 p. microscopic marine organism Mesodinium rubrum in Pas samaquoddy Bay, N.B., in July 1979. The photo shows six square metres of water surface with highly discoloured small patches contain ing several million M. rubrum cells per litre. (Photo: Bill McMullon)

Published by: Communications Branch Department of Fisheries and Oceans Ottawa, Ontario K1 A OE6

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