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. (Peter Franks, Scripps Institution of Oceanography.)
An interference contrast light microscope image of cysts of the toxic alga Alexandrium tamarense. (Photo by David Wall)
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. (G. Early.)
Japanese fish farmers inspect their ruined crop of yellowtail following a devastating red tide. (M. Aramaki.)
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.
Reports of harmful algal blooms in U.S. waters and around the world have drastically increased in the past three decades. Researchers attribute the increase partly to excessive nutrient pollution of the water and partly to better detection of HABs by coastal monitoring programs. (Don Anderson and Jayne Doucette, WHOI Graphic Services.)