The Growing Problem of Harmful Algae Tiny Plants Pose a Potent Threat to Those Who Live in and Eat from the Sea

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The Growing Problem of Harmful Algae Tiny plants pose a potent threat to those who live in and eat from the sea

By Donald M. Anderson without income for nearly two months at primary energy producers in the ocean, Director, Coastal Ocean Institute a time when they typically fill their bushel forming the base of the marine food chain. Senior Scientist, Biology Department Woods Hole Oceanographic Institution baskets and wallets. From Nova Scotia to In the presence of sunlight and a sufficient Cape Cod, restaurateurs watched the price bath of nutrients, these single-celled plants uly and August 2004 — At the height of of clams jump by 200 percent. All of this photosynthesize and multiply, creating a Jthe summer season, when New England- was caused by a tiny microscopic organism, “bloom” that feeds everything from fellow ers and thousands of tourists open their Alexandrium, which does not harm the microbes to great fishes. wallets to buy fresh “steamers” and fried clams but can sicken or kill humans who Among the thousands of species of clam strips, Maine’s shellfish beds are shut eat the shellfish. algae in the sea, a few dozen produce tox- down. Concerned by the worst bloom of ins and pose a formidable natural hazard. toxic algae in 23 years, resource managers Millions of microscopic plant cells Sometimes they reproduce prolifically, closed the flats for fear of paralytic shellfish thrive in nearly every drop of coastal discolor the water, and foul beaches with poisoning. Hundreds of shellfishermen went seawater. Algae (phytoplankton) are the foam from their prodigious population Peter. Franks, Scripps Institution of Oceanography Franks, Peter. A massive “red tide” of blooming algae (the dinoﬂagellate Noctiluca scintillans) stretched more than 20 miles along the coast near LaJolla, California in the spring of 1995. Such blooms can have devastating effects on human health, coastal economies, and marine ecosystems. Algal blooms occur naturally, but they have become much more common in recent years, some due to human activities that put excess nutrients into the water.

1 Oceanus Magazine • Vol. 43, No.1 • 2004 Woods Hole Oceanographic Institution • oceanusmag.whoi.edu ��

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�� Don Anderson and WHOI Graphic ServicesDon Anderson and Certain species of toxic algae—in this case, Alexandrium—have evolved a cyst stage in their life cycle that promotes wide dispersal through the coastal ocean and long-term survival through difﬁ cult environmental circumstances.

booms. Other times these harmful algae they are not new. But ocean scientists are algal species. Bloom events can cover are dilute and invisible, nearly inconspicu- growing concerned that they are now all areas as small as a coastal pond or as large ous if not for the destruction they cause. too common. The unprecedented growth as one million football fields (more than A bloom of harmful algae can completely of human activities in coastal water- 1,000 square miles). and permanently alter the structure of a sheds—including agriculture, aquaculture, These blooms of algae are popularly food chain, causing massive die-offs of industry, housing, and recreation—has known as “red tides,” since the tiny plants shellfish, marine mammals, fish, seabirds, drastically increased the amount of fertil- can sometimes increase in such abun- and other animals that consume them. izer flowing into coastal waters and fueled dance that until they change the color of They can sicken, disable, or kill humans. unwanted algal growth. the water with their pigments. The term Researchers estimate that blooms of is misleading because non-toxic species harmful algae cost the United States at A growing plague also can bloom and discolor the water, least $50 million per year. The economic And Moses...lifted up the rod, and smote and other species are incredibly toxic damage arises from: the waters that were in the river, in the sight even when concentrations are low and the • the death of wild and farmed fish, of Pharaoh, and in the sight of the servants; water seems clear. Given the confusion shellfish, submerged aquatic vegeta- and all the waters that were in the river surrounding the meaning of “red tide,” tion, and coral reefs turned to blood. And the fish that were in the scientific community prefers the term • short- and long-term closure of har- the river died; and the river stank, and the harmful algal bloom, or HAB. vestable shellfish and fish stocks Egyptians could not drink of the water of One cause for the increasing frequency • reductions in seafood sales, including the river; and there was blood throughout of HAB events seems to be nutrient en- the avoidance of “safe” seafood due to the land of Egypt. — Exodus 7:20-21 richment—that is, too much “food” for the over-reaction to health advisories algae. Just as the application of fertilizer to • the costs of conducting monitoring Red tides have been known through- lawns can enhance grass growth, marine programs to detect and quarantine toxic out recorded history, but the nature of the algae grow in response to nutrient inputs shellfish and other affected resources global problem in estuaries and coastal from domestic, agricultural, and industrial • impacts on tourism and related waters has changed considerably over the runoff Nutrient enrichment leads to exces- businesses last several decades, both in extent and in sive production of organic matter (includ- • medical treatment of exposed public perception. ing HABs) and a reduction in the amount populations. Virtually every coastal country is of life-giving oxygen dissolved in the wa- Harmful algal blooms are natural and threatened by multiple harmful or toxic ter, a process known as eutrophication.

2 Oceanus Magazine • Vol. 43, No.1 • 2004 Woods Hole Oceanographic Institution • oceanusmag.whoi.edu Life cycle of a bloom ing to an end, the algae form thick-walled, been healthy immediately prior to their Fall 1972 — Over Labor Day week- dormant cells called cysts that settle to deaths; no lesions or infectious pathogens end, Tropical Storm Carrie blows into New bottom sediments. These cysts can survive were detected; and many whales had fish in England and becomes a Nor’easter, batter- for years, allowing a species to withstand their stomachs as evidence of recent feeding. ing the coast with heavy winds and rain. nutrient starvation, extreme winter tem- Alarmed and saddened by the mysterious Unbeknownst to scientists, cells of Alexan- peratures, or even ingestion by animals. deaths, the public and the press speculated drium fundyense (algae native to the Bay When favorable conditions resume, the that they were caused by pollution. Scien- of Fundy) are washed south and west by cysts rupture, germinate, and populate the tists later discovered that the whales had currents stirred by the storm. Several weeks water column with a new generation of consumed mackerel with an abundance of after Carrie, a massive bloom of shellfish- photosynthetically active cells primed for algal toxins stored in their flesh. poisoning algae blankets the waters of New another bloom. England. Before 1972, toxins associated The cyst stage represents an effective Algal blooms can have an impact even with A. fundyense had not been recorded strategy for survival and dispersal. With if whales, wild fish, seabirds, and other in western New England waters; since then, every switch into the cyst stage, a bloom animals do not consume the microscopic that species has bloomed nearly every year. can be carried into new waters by ocean cells. Some algae release their toxins and currents, fish, or even humans (via ballast other compounds into the water, killing Algae usually reproduce by asexual water discharge) and then deposited as a creatures through direct exposure. Car- fission: One cell grows and then divides “seed” population that colonizes a new area. nivorous fishes and mammals sometimes into two cells, then two into four, four into die from the cumulative effects of con- eight, and so on. When growth is un- Quiet killers suming smaller fish or zooplankton con- checked by environmental conditions— November 1987 — Over a five-week taining toxins. such as grazing by animals or a shortage of span, 19 humpback whales die in Cape Other HABs kill without toxins. The nutrients or light—harmful algae popula- Cod Bay, Massachusetts, a die-off equiva- species Chaetoceros has been associated tions can accumulate to visually spectacu- lent to 50 years of natural mortality. Unlike with the deaths of farmed salmon, yet lar but catastrophic levels. stranding events, where seemingly healthy these tiny plants do not produce a toxin at For some species, a decline in avail- whales swim into shallow water and beach all. Instead they have long, barbed spines able nutrients provokes a switch to sexual themselves, these humpbacks were dying that lodge in fish gills, causing a buildup reproduction and a new life stage. When at sea and washing ashore. Post-mortem of mucus, degeneration of the respiratory they sense that their boom times are com- examinations showed that the whales had system, and eventual death by suffocation. Credits: G. Early (left), M. Aramaki (right), and D. Wall (background) Wall G. Early (left),Credits: M. Aramaki (right), and D. Left: A dead humpback whale washed up on the shores of Cape Cod, Mass., as a result of a harmful algal bloom in November 1987. Nineteen seemingly healthy whales died after consuming mackerel laced with an algal toxin. Right: Japanese ﬁ sh farmers inspect their ruined crop of yellowtail following a devastating red tide. Background: Scanning electron microscope view of cysts of the toxic alga Alexandrium tamarense.

3 Oceanus Magazine • Vol. 43, No.1 • 2004 Woods Hole Oceanographic Institution • oceanusmag.whoi.edu Some blooms deplete the resources HABs can take a variety of forms, each needed by marine creatures. For with a distinct and disturbing impact on instance, when a massive bloom human health. begins to decay, the dying and �� • Shellfish poisoning — Most decomposing algae consume the avail- shellfish filter seawater for able oxygen, suffocating other plants and food. As they eat, they some- animals or forcing them to migrate. • Occasional anoxia times consume toxic phyto- Prolonged blooms of non-toxic algae plankton and the algal toxins ac- also can reduce light penetration to the cumulate in their flesh. The level of bottom, decreasing the density of aquatic toxins can reach a threshold where vegetation and grass beds that serve they become dangerous—sometimes as nurseries for commercially im- lethal —to humans and other animals, portant fish and shellfish. Hawaii though not to the shellfish themselves. Blooms of macroalgae (seaweeds) Shellfish poisoning syndromes have also increased along the world’s Puerto Rico can cause gastrointestinal and

coastlines, and they often last longer Neurotoxic shellfish poisoning Pfiesteria Complex neurological problems, from than typical phytoplankton blooms. Paralytic shellfish poisoning Farmed Fish Kills nausea, vomiting, and incapaci- Once established, macroalgae can domi- Ciguatera Amnesic shellfish poisoning tating diarrhea to dizziness, dis- Brown Tide nate an ecosystem for years and are par- orientation, amnesia and perma- ticularly harmful to coral reefs. Under nent memory loss, and paralysis. the right conditions, opportunis- Some syndromes are lethal. tic seaweeds outcompete, over- • Ciguatera fish poisoning — grow, and replace the coral. �� Species of the genus Gambier- These chronic impacts can affect discus living in tropical waters the structure and function of entire eco- (particularly coral reef commu- systems. The mass die-off of adult fish nities) are known to produce • Occasional anoxia not only depletes the current popula- • Diarrhetic shellfish poisoning (unconfirmed) a fat-soluble toxin that causes tion, it prevents breeding-age fishes • Marine mammal mortalities diarrhea, vomiting, and abdominal (whales, manatees, sea lions, dolphins) from reproducing. Larvae or juvenile • Noxious blooms (aesthetics) pain, followed by muscular aches, fish can be stunted or killed, preventing • Macroalgal blooms dizziness, anxiety, sweating, and tin- the next generation from reaching gling sensations. Ciguatoxin-produc-

maturity. Hawaii ing algae live attached to seaweeds, and Such ecosystem degradation they are first consumed by plant-eat- likely has long-term consequences for ing reef fishes. Those fish are in turn the sustainability or recovery of popula- Puertoeaten Rico by larger carnivorous, commer- tions of animals further up the food chain. Reports of harmful algal blooms in U.S. cially valuable finfish. The toxin, being A population of marine mammals might waters and around the world have drastically fat soluble, is transferred and magnified not grow or reproduce because their main increased in the past three decades. through the food chain, much as occurs food source has been depleted by HABs. Researchers attribute the increase partly to with pollutants such as DDT and PCBs. Many researchers now believe that such excessive nutrient pollution of the water and That means the most dangerous fish to ecosystem-level effects from HABs are partly to better detection of HABs by coastal eat are the largest, oldest, and most desir- more pervasive than we realize. monitoring programs. able. Ciguatera is responsible for more Don Anderson and Jayne Doucette, WHOI Graphic Services human illnesses—10,000 to 50,000 cases Watch what you eat annually—than any other kind of toxicity February to April 1998 — In Hong tatum. Direct losses are estimated to be originating in fresh seafood. Kong, where one-third of all finfish con- HK$250 million ($32 million U.S.). Other • Possible Estuary-Associated Syn- sumed comes from fish farms, a devastat- fish prices plummet as consumers avoid drome — This vague term reflects the ing HAB wipes out half of the country’s seafood altogether. A government official poor state of knowledge of the human annual aquaculture fish stocks. More than calls it the “worst natural disaster” ever to health effects of the alga Pfiesteria pi- 1,500 tons of fish are killed by a neuro- hit Hong Kong. scicida and related organisms. Human toxin-producing alga called Karenia digi- exposure to these algae in estuaries has

4 Oceanus Magazine • Vol. 43, No.1 • 2004 Woods Hole Oceanographic Institution • oceanusmag.whoi.edu January 9, 2002 February 18, 2002 March 20, 2002 Courtesy of SeaWiFS Project, NASA Goddard, and ORBIMAGE NASA Goddard, Courtesy Project, of SeaWiFS In the winter of 2002, satellites and sailors observed waters in Florida Bay, turning the color of black ink. Researchers speculated that the mysterious “black water” was a bloom of algae, though there were none of the typical signs of toxins or oxygen depletion and no observed die- offs of marine life. Fishermen noted that they found few ﬁsh within the region.

been linked to deficiencies in learning (two-thirds the size of Rhode Island) tak- Researchers suspect that many “new” and memory, skin lesions, eye irritation, ing on the color of black ink. Tests show bloom species are simply “hidden flora” and acute respiratory distress. In 1997, a this “black water” has normal salinity and that had existed in those waters for many bloom of Pfiesteria caused massive fish oxygen levels, but researchers suspect an years. Such species had not been detected die-offs on Maryland’s eastern shore, lead- unusual, non-toxic algae bloom. There are or recognized as harmful until scientists ing consumers to avoid all seafood from none of the usual signs of a HAB, but fish- had developed more sensitive toxin detec- the region despite assurances that no tox- ermen note that the black water seems to tion methods and trained more observers, ins had been detected in seafood products. be devoid of fish. or until aquaculturists had placed shellfish That single event cost at least $50 million or fish resources in areas where toxic spe- in lost seafood sales and lost revenues for Researchers call the recent expansion cies had been lurking. recreational boat charters. of HABs an “apparent” trend because for That part of the expansion may be a many locations, poor historic data are avail- result of increased awareness should not Increasing awareness able. It is not clear whether the increase in negate our concern, nor should it alter January and February 2002 — Seafar- HAB reports reflects heightened scientific the manner in which we mobilize re- ers and satellites notice something amiss awareness of coastal waters and scrutiny sources to attack it. The fact that harmful in the Gulf of Mexico. The seas north and of seafood quality, or a real increase in the algal blooms are at least partly due to hu- west of the Florida Keys have grown dark, number, severity, or frequency of outbreaks man activities makes our concerns even with nearly 700 square miles of water due to pollution and global change. more urgent.

Donald M. Anderson is a Senior Scientist in the Biology Department of the Woods Hole Oceanographic Institution, where he also serves as Director of the Coastal Ocean Institute. He earned a bachelor’s degree in mechanical engineering and a doctoral degree in aquatic sciences from the Civil Engineering Department of the Massachusetts Institute of Technology. He accepted a postdoctoral position at WHOI in 1978 and joined the staff as an Assistant Scientist in 1979. Anderson became interested in red tides and HABs as an MIT graduate student when a massive red tide devastated the New England coast. His work investigating chemical factors regulating Alexandrium blooms led to discoveries of a cyst stage and other biological processes that became his research focus. Since then, his research program has expanded and now ranges from molecular and cellular studies of toxin genetics to large-scale studies of the oceanography and ecology of algal blooms. He is actively involved in the organization and implementation of national and international programs for research and training on HABs. He serves as director of the U.S. National Office for Marine Biotoxins and Harmful Algal Blooms (based at WHOI). The National Oceanic and Atmospheric Administration named him an “Environmental Hero” in 1999. He does eat shellfish and other seafood, both at home and abroad, but is careful to learn whether the product is from approved waters. As a rule, he does not eat large, tropical reef fish. Don is an accomplished golfer, and is currently the Massachusetts Senior Amateur Champion.

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