Algea bloom on Lake Erie

The green in this image captured on Oct. 5, 2011, is the worst algae bloom Lake Erie has experienced in decades. The bloom is primarily microcystis aeruginosa, an algae that is toxic to mammals, according to the Great Lakes Environmental Research Laboratory. Several days of calm winds and warm temperatures allowed the algae to gather on the surface. Such blooms were common in the 1950s and 60s when phosphorus from farms, sewage, and industry fertilized the waters. The blooms subsided starting in the 1970s, when improvements in agriculture and sewage treatment limited the amount of phosphorus that reached the lake. But this year a giant bloom spread across the western basin once again. The reasons for the bloom are complex, but may be related to a rainy spring and invasive mussels. (Source: NASA/Landsat-5)