This remarkable image of the Great Lakes Region shows a nearly cloudless day over the northern United States and southern Ontario, Canada. The Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite captured this true-color image on August 28, 2010 as it passed over the region.
In true-color images, dark green indicates areas of dense vegetation, such as forest and/or wetlands. Lighter green indicates less vegetated areas, and is often typical of agricultural land. When this image is viewed at high resolution, much of the light green areas in the northern United States, such as in Michigan, evidences a cross-hatched pattern, suggestive of agricultural activity. Human activity can also be seen as areas of gray, which indicate cities, such as Chicago, Illinois at the southwestern tip of Lake Michigan and Toronto, Canada at the at the northwestern tip of Lake Ontario.
The Great Lakes appear as varying shades of blue, with some patches of white and swirls of green. From west to east lie the five Great Lakes: Lake Superior, Michigan, Huron, Erie and Ontario. South of Lake Ontario can be seen slit-like wedges of blue indicating New York State’s Finger Lakes. The turquoise-green swirling patterns in Lake Erie are typical of an algae bloom.
The most common algae in Lake Erie are colloquially called “Annie, Fannie and Mike”, nicknames for anabaena, aphanizomenon, and microcystis. Microcystis, which has been identified as the major organism in the current algae bloom, is a cynanobacter – bacteria which can photosynthesize, producing a green color. Summer blooms of algae are common in Lake Erie, but extensive blooms such as this are both unusual and undesirable.
Cyanobacter produce both neurotoxins and liver toxins, which are potentially harmful to life in the lakes. The Ohio Environmental Protection Agency is one authority which tests waters showing signs of algae bloom for these toxins, and provides public advisories when levels become elevated.