Volume 15, Number 4 • July-August 1997

Harmful Algal Blooms on the Move

By Merrill Leffler

If toxic algae, or harmful algal blooms, as they are now referred to, are rare to the Chesapeake Bay, that is not the case for coastal regions nationwide and throughout the world.

Reports come in each year of thousands of floating dead fish from the Gulf of Maine, from the coast of Florida and from the Gulf of Mexico killed by toxic algae. Of 4,400 marine phytoplankton species, only 50 to 60 are toxin producers - a mere 1.3 percent, though the impact of these few species can be significant. The toxin producers can injure or damage fish, or they can be taken up by shellfish and then passed along to human consumers, potentially causing paralytic or diarrhetic shellfish poisoning.

The scientific consensus is that outbreaks of harmful algal blooms are escalating in frequency and extent. Just how much of that escalation is due to natural environmental change such as rising sea level, for example, and how much results from human activities, remains uncertain. Increasing nutrient runoff in most populated nearshore areas and the shifting of organisms from one ecosystem to another in the millions of gallons of ballast water ferried around the world by cargo ships could be important factors.

What is certain is that the effects of these blooms are significant. The economic impact of fish kills and closed beaches has been estimated at tens of millions of dollars over the last two decades. In addition, researchers worry about the ecological changes that can occur as concentrated neurotoxins work their way up the food chain. These economic and biological concerns have spurred legislators to establish a new federal program that will support long-term research aimed at unraveling the processes that foster such blooms.

That program - the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) - is a multi-agency undertaking and includes the National Science Foundation, the Environmental Protection Agency, the Office of Naval Research and the National Oceanic and Atmospheric Administration's Coastal Ocean Program, which is taking the lead in this effort.

Economic and biological concerns have spurred legislators to establish a new federal program that will support long-term research aimed at unraveling the processes that foster such blooms.

The goal, says Kevin Sellner, is to develop a much better understanding of how biological and physical processes interact to promote algal blooms. Sellner, a scientist at the Academy of Natural Sciences Estuarine Research Center in St. Leonard, Maryland, is on a two-year assignment at NOAA's Coastal Ocean Program, where he is heading up ECOHAB. In the long run, he says, we need to better predict their occurrence if there is to be any chance of taking actions that can reduce their impact.

The extent of concern over harmful algal blooms can be gauged from a web site overseen by the National Office for Marine Biotoxins and Harmful Algal Blooms (http://www.whoi.edu/redtide/) that has links to regional research programs and regularly updates reports of toxic red tides in coastal areas. The office's Director, Donald M. Anderson of the Woods Hole Oceanographic Institution, is one of the country's leading authorities on algal blooms. Together with Sylvia Galloway and Jeanne Joseph, he authored Marine Biotoxins and Harmful Algae, a national plan that set out the priorities for understanding the causes and behavior of harmful blooms.

This document concludes that the United States research, monitoring and regulatory infrastructure is not adequately prepared to meet this threat. The panel recommends a more proactive approach on the part of agencies. (Fish kill responses, for example, are often too late to identify causative organisms, and often the appropriate tests are not conducted.) The plan recommends development of expertise and tools (including molecular probes) to facilitate sampling for toxic species and the presence of biotoxins, and the use of computer technologies to communicate the information quickly to users and the research community.

Most recently, Donald Boesch, President of the University of Maryland Center for Environmental Science, chaired a scientific committee that, as a complement to the research plan, examined the management options for controlling harmful blooms. Those options are limited, given the extent of our understanding of how physical and biological processes interact to regulate the extent of such blooms. The committee's report, Harmful Algal Blooms in Coastal Waters: Options for Prevention, Control and Mitigation, acknowledges that while there is a compelling link between increasing algal blooms and overenrichment of coastal waters, it has not been unequivocally identified as the cause of any harmful algal blooms considered in its assessment. Still, says the report, the goal of reducing excess nutrients "could well yield positive results in terms of reductions in some harmful algal blooms."

To order a copy, contact the NOAA Coastal Ocean Office by phone, (301) 713-3338, or fax, (301) 713-4044.

Some Culprits

These organisms are some of those responsible for harmful algal blooms in U.S. coastal waters. The drawings and the information below are from Harmful Algal Blooms in Coastal Waters produced by the NOAA Coastal Ocean Program.

Gymnodinium breve, a dinoflagellate, produces neurotoxic shellfish poisoning along the coasts of the Gulf of Mexico and, rarely, the southeast Atlantic coast.
Various species of the dinoflagellate genus Alexandrium are responsible for paralytic shellfish poisoning in New England, northern California, the Pacific Northwest and Alaska.
Aureococcus anaphagefferens, a small golden brown algae, is responsible for brown tide blooms in southern New England, particularly Long Island, and in New York and Texas. Aureoumbra lagunensis, a similar species, causes blooms in Texas bays and lagoons.
Blooms of various species of the diatom genus Pseudo-nitzschia produce domoic acid that causes amnesic shellfish poisoning on the northwest, east and Gulf coasts.
The raphidophyte flagellate Heterosigma akashiwo and a few species of the diatom genus Chaetoceros cause catastrophic losses of cultured and wild fish, particularly in the Pacific Northwest.

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