Climate Change Affects Harmful Algal Blooms
Scientists Connect Global Warming and Nutrient Runoff to HABs
Aug 29, 2008
Scientists worldwide have observed a marked increase in coastal and freshwater algal blooms in the past decades, variously suggesting this may be from the introduction of exotic species (G.M. Hallegraeff, 1993, "A review of harmful algal blooms and their apparent global increase", Phycologia 32(2):79-99) and grazers failing to control algal growth (Rosetta and McManus, 2003, "Feeding on ciliates on two harmful algal species, Prymnesium parvum and Prorocentrum minimum", Harmful Algae, Vol. 2, Issue 2: 109-126).
K.G. Sellner, G.J. Doucette and G.J. Kirkpatrick suggested climate change combined with human activities, primarily through nutrient runoff, is important in increased HABs (2003, "Harmful algal blooms: causes, impacts and detection", Journal Ind. Microbiol. Biotechnol. 30:383-406).
Ancient Blooms Prevail to Current Times
Algae have flourished for 2.7 billion years, forming "blooms" along coasts and in lakes under favourable light, temperature and nutrient conditions. In freshwater, they can form blooms like pea soup. In marine environments some spread across the sea floor “fast enough to cover a football field in an hour,” according to Kenneth Weiss ("A Primeval Tide of Toxins", July 30, 2006, L.A. Times). Every summer algal blooms turn parts of the Baltic Sea coast “into a stinking yellow-brown slush that locals call rhubarb soup."
Toxic blooms (HABs) occur when algal species produce neurotoxins, usually when stressed or dying. Unwitting fishermen get splashed and break out in searing welts, blistering, peeling lips, and burning, swelling eyes. Some people have problems breathing.
Climate Affects Algal Growth in the North Sea
Mounting evidence, including recent work in the North Sea, links climate change to HABs. In studies off the coast of Netherlands, Louis Peperzak concluded that dinoflagellate and raphidophyte blooms will increase due to increased temperatures and salinity stratification resulting from climate change ("Climate change and harmful algal blooms in the North Sea", Acta Oecologia, May 2003).
Oregon State University scientists attributed the increased HABs that have closed shellfish harvests and caused "red tides" in the Pacific Northwest to a combination of global climate change and increased human impact in coastal zones.
"Harmful algal blooms are the negative side of coastal upwelling," Peter Strutton, assistant professor in OSU's College of Oceanic and Atmospheric Sciences, and co-principal investigator of the study, said. (OSU News & Communication Service, "Harmful Algal Blooms Increase; Researchers Seek Warning Signs", September 29, 2005.) "There is growing evidence that these blooms have been increasing over the last 20 years and not only are becoming more frequent, but more intense and with longer duration. We also are starting to record toxic events in places that haven't had them, ... they may be spreading."
Nutrients Key to HAB Increase in Lakes
In a July 22, 2008 interview with Ed Struzik of the Times Colonist, "Scientists solve riddle of toxic algal blooms", Canadian limnologist David Schindler suggested, "Phosphorous really is the key," for the increase of HABs in freshwater, citing increased industrialization and urban growth. After 37 years of experimentation on a small pristine lake, Schindler determined that nitrogen removal completely failed to control blue-green algae blooms; nitrogen control only encouraged algae blooms.
A Future Primitive Sea?
“There’s no silver bullet or quick fix for this,” said Associate Professor Ron Johnstone, Australia's Coastal Resource Management Coordinator to Weiss of the NY Times, July 30, 2006 in "A Primeval Tide of Toxins". Jeremy Jackson, marine ecologist at Scripps Institution of Oceanography (in the same article) warns that climate change may evoke a return to the primitive seas of half-billion years ago when jellyfish and bacteria dominated.
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