The study -- the first ever to rate the effectiveness of various computer models for monitoring the Great Lakes -- might also aid studies of global climate change.

As algae flourishes in the five freshwater lakes every summer, satellite images show the water changing color from blue to green, explained Carolyn Merry, professor of civil and environmental engineering and geodetic science.

When algae levels are too high, water takes on a foul taste and odor that isnt easily removed by traditional treatment methods. Some forms of algae, such as one called microcystis, are toxic when consumed in large quantities. Though it can be filtered out of drinking water, microcystis can kill fish and birds, and coastal communities often have to ban swimming and water skiing in the summer when the algae blooms.

Computer models enable scientists to measure the color of light reflected from the water to gauge how much algae is present in a lake, and where. The problem: all the available models of this type were originally designed for sea water, not lake water.

Theyve got it down pat for the ocean, Merry said of the various models developed by NASA and other agencies over the years. But lakes are shallower and have different water conditions that affect the wavelengths of light collected by the satellites, so we can get erroneous measurements.

Merry and masters degree student Raghavendra Mupparthy reported the results of an initial study of Lake Erie May 25 in Denver at the meeting of the American Society for Photogrammetry & Remote Sensing. They determined which four of the top ocean models may perform well for studies of the Great Lakes.

Most scientists look for evidence of climate change in the oceans rather than in lakes, but that may change in the future, the engineers said.

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Contact: Carolyn Merry
Merry.1@osu.edu
614-292-6889
Ohio State University
25-May-2004