Take a typical drop of water and what do you see? Thousands of microscopic algae -- tiny floating organisms with a rich diversity of species that serve as the ultimate source of food for all marine life. The tiny plant algae contain all the cellular machinery to make food from sunlight and nutrients.
Although algae are an important part of the ecosystem, a few dozen species are known to be harmful. These species can cause fish to die in great numbers, contaminate seafood with toxins, cause serious human health problems and impact marine ecosystems in many other ways.
Some of these harmful algae species can multiply in great numbers to form "blooms" -- visible scum or discolorations of water. These are often called "red tides" because of the reddish-brown color that appears in the water from the pigments contained in these little cells.
Different species that are actually toxic to shellfish, fish and even people also can grow rapidly in the water. Although sometimes difficult to detect, these toxic algae can still be potent enough to poison seafood. Collectively these events are termed "harmful algal blooms."
The most serious impact of harmful algal blooms is the risk of seafood poisonings. Different algae make different toxins and they result in various poisoning syndromes when eaten, but the effects can be serious and deadly -- more than 2000 people are poisoned and several hundred die each year around the world.
In some cases, the poisonings are short-lived, and the only effects are cramping, diarrhea or vomiting. In other cases, long-lasting neurological conditions develop. Allergies and skin rashes are also associated with some of these species.
Residents of Florida know well that respiratory problems can occur when red tides develop and winds carry the air-borne toxins over land. The effect can also cause short-term memory loss or paralysis. It is believed that the real number of illnesses due to harmful algae may be much higher because of incorrect diagnoses, lack of appropriate medical facilities and unwillingness of some people to seek medical help.
Most developed areas of the world known to have toxin-producing algae are monitored vigilantly. Health warnings are posted whenever there is danger of an outbreak. Strict seafood inspections in the United States ensure the safety of all product that goes to market.
Even so, last year nearly a dozen people were hospitalized in Washington state after ignoring posted warnings and collecting and eating contaminated mussels from the beach.
Another serious impact of harmful algae is economic loss following large fish die-offs or "fish kills" and, at the extreme, collapse of entire seafood industries. The economic costs of harmful algae are rapidly expanding around the world.
Japan now considers fish kills in and near aquaculture sites due to harmful algae a serious economic problem. Fish-farm kills in Scandinavia are now common and massive stranding of rock lobster following harmful blooms are now regularly reported in South Africa. Human poisonings in Mexico following oyster consumption are a frequent occurrence. In China, harmful bloom events, rare occurrences two decades ago, now are frequent and large in scope and duration.
In September 2001, 3,000 tons of fish died in Kuwait and seafood markets across the country were closed due to a bacterial infection that spread following a harmful algal bloom. On Long Island, N.Y., the scallop industry has been devastated from the development of blooms known as "brown tides," which first appeared in the mid-1980s but have since re-occurred annually.
In Maryland, following the 1997 fish kills associated with outbreaks of the highly toxic species Pfiesteria, economic losses over $40 million dollars were estimated to the seafood market, including wholesalers, retailers and restaurants.
Just as consumer responded negatively to the mad cow disease outbreak in Europe, when a particular food product is suspected by the public to be tainted, they stop buying it.
Harmful blooms have received much attention in the media over the past several years, but they are not a new phenomenon. Many of the journals of early explorers contain references to what apparently were harmful blooms. Similar tales are woven into the fabric of legends and lore in many seaside areas.
As far back as 1770 in Australia, Captain Cook recorded in his log, "The sea in many places here is cover'd with a kind of brown scum." A few years later, some of Captain George Vancouver's men died after eating shellfish taken from what has become known as "Poison Cove" in British Columbia, Canada.
What seems to be new about the growth of these toxic species is that the impacts of many harmful algal blooms may be increasing worldwide. Why? There are many possible reasons for global expansion -- including the belief by doubters who think the increased reports are due to better techniques to detect these organisms.
A leading theory is that these species are being introduced to new regions around the world. Many marine species are regularly transported around the globe by shipping and ballast water dumping, and through transport of live fish stocks in the rapidly expanding aquaculture industry.
Other factors, such as global climate change, also may be contributing to the spread of species to new regions. Warm temperatures, lots of sunlight and an excess of nutrients such as nitrogen and phosphorus provide ideal conditions for these cells to grow.
Pollution of our coastal waters is probably one of the major causes of the expansion of harmful bloom events, at least in some regions. Microscopic algae require many of the same nutrients used as fertilizers to grow lawns, crops and gardens. Plants, including microscopic ones, grow better when there are more nutrients available and they can attain higher densities in the water.
Just as in fertilizing a lawn, however, the grass may grow better but so do the weeds. More and more development along coastal lands leads to more sewage, more fertilizers and more pollution.
Microscopic cells have a huge range of diversity. For this reason, certain species grow only under specific environmental conditions. As the quantities of nutrients have increased in many regions, the types of nutrients that are entering the waters also have changed. These changes may have profound consequences for the microorganisms.
Different crops require fertilizer formulas and growing grass, roses or tomatoes requires different proportions of nitrogen and phosphorus, all of which could be selectively stimulating harmful species in the water. Many harmful species have fascinating and very effective mechanisms for scavenging nutrients from a range of sources and out-competing the algae that would otherwise grow and lead to healthy waterways.
Research on harmful algae has advanced significantly in past decade. Fortunately, in many places, these blooms are no longer viewed as local problems with local solutions. The U.S. ECOHAB Program -- funded jointly by several federal agencies, including the National Oceanic and Atmospheric Administration, the National Science Foundation and the Environmental Protection Agency -- has allowed researchers to study how similar species may grow in comparative regions, to develop sophisticated models to aid in the prediction of their occurrence, and to evaluate new approaches for easing the impact of harmful algae.
Efforts to bring researchers together from around the world are also developing. Research programs from Europe to China are expanding as this threat to human health and coastal economies becomes more widely recognized.
Although these efforts are recent, they show great promise.
(Dr. Gilbert is with the Horn Point Laboratory at the University of Maryland's Center for Environmental Science in Cambridge.)
