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Green seeds, red tide

Harmful algae blooms (“red tide”) commonly occur in the Gulf of Maine in spring. Blooms result from the rapid reproduction of toxic algae called Alexandrium when their seed-like resting stages (“cysts”) on the sea floor germinate and grow. WHOI scientists have developed a computer model to predict the intensity and locations of blooms based on the abundance of cysts in the seafloor sediment and other environmental factors. The model successfully forecast the 2008 bloom. Stained with a green fluorescent dye, cysts of the toxic algae, Alexandrium fundyense and Alexandrium tamarense stand out under the microscope. (Photo by Kerry Norton, Woods Hole Oceanographic Institution)