By KIMBERLY HIRAI
Capital News Service
One of the Environmental Protection Agency’s newest members uses side-scan sonar to look at the watery depths of Lake Michigan.
Fanning its sound waves down to the lake floor, it searches for the returning signals bouncing off the bottom in search of bounty – and found a shipwreck last year.
But the Triaxus Towed Undulator does more than hunt treasure. Beneath the water, it glides behind the Lake Guardian, the agency’s research vessel based in Chicago.
The actual Lake Guardian research vessel is used to sample and study all of the Great Lakes. However, it is operated by the Chicago-based Great Lakes National Program Office.
With its quick data collection, the agency can do in days what would otherwise take a year, said Glenn Warren, team leader for the agency’s environmental monitoring and indicators group in the Great Lakes National Program Office in Chicago.
The Triaxus, weighing more than 250 pounds and standing more than 4 feet high, studies the water and the lake bottom. Its sensors calculate oxygen amounts, test water quality, count plankton, measure chlorophyll and analyze nitrate while viewing the bottom with sonar.
EPA purchased the Triaxus in May 2008 for about $750,000 and first used it to examine parts of Lake Ontario. The agency began its study of Lake Michigan last fall and plans to do at the least the U.S. part of Lake Superior.
The goal is to provide a general view of nearshore patterns. The nearshore begins at the shoreline and reaches a water depth of about 30 feet.
“Once we get that information we can perhaps develop indicators based on the different sensory information,” he said. “Then we can start comparing that year to year.”
For example, Warren said, if EPA researchers knew the area where a river entered the lake, they could determine chlorophyll and zooplankton levels at that point within the nearshore area. Those measurements could be compared with past years’ to see how the river affected the nearshore.
The data gaps are real, as is the need to fill them.
“The difficulties are that it’s a variable environment, so you can go along the shore and get very different chemical and biological readings for measurements and that has led to people not sampling it very frequently or very well,” he said.
Kimberly Hirai writes for Great Lakes Echo.