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Researchers use Sea Grant support to study nutrient pollution in Green Bay ecosystem

Awareness is growing regarding nutrient pollution in America’s waters.  An overabundance of phosphorus, for example, causes algae to grow faster than ecosystems can handle. This results in negative effects for fish and other aquatic life, human health and the economy.

New technologies are making it easier to measure phosphate in the water. Michael Zorn, a professor of chemistry at the University of Wisconsin-Green Bay, is pursuing research that uses the latest in phosphate-sensing technology to learn more about the compound’s dynamics as it proceeds from Lake Winnebago to Green Bay through the Lower Fox River.

Zorn’s research project is funded by Wisconsin Sea Grant. Among other things, funding allowed him to purchase two high-tech phosphate sensors (to supplement an existing one) and hire a graduate research assistant, Erica Meulemans, to help with the project.

The project is called “Extreme Events, Watershed Loadings and Climate Change: Implications for the Management and Long Term Health of the Green Bay, Lake Michigan Ecosystem.”

Zorn and his collaborators used the three high-tech phosphate sensors in combination with more traditional sensors and focused on three key locations. The first was on the property of ThedaCare, a health care provider in Neenah, to capture water just coming into the Lower Fox River.

The second sensor was deployed at a midway point, the Little Rapids Lock and Dam, downstream of some sites where significant amounts of phosphorus are entering the waters.

Finally, the third sensor was set up on the west side of Green Bay, at the U.S. Oil Depot near the bay of Green Bay. The sensors measure dissolved phosphate in the water.

The key benefits of the new-style sensors are the frequency and accuracy of the readings they provide, as well as the ability to monitor them remotely by logging in to a website that the United States Geological Survey (USGS) helped set up.

Said Zorn, “Without high-frequency data like this, it’s hard to know exactly what’s happening. When samples are collected on a weekly basis, a lot of the short-term ups and downs [in phosphate levels] are missed. Going into this project, we didn’t know how fast things were going to change; it was a big unknown.”

With Zorn’s Sea Grant project, the advanced sensors measure phosphate levels every one to two hours, representing a dramatic improvement over how things have been done in the past.  “If you just plotted a sample per week, you’d miss a lot of that short-term variation,” explained Zorn, who also serves as associate dean of the College of Science, Engineering and Technology on the UW-Green Bay campus.

“There are even some regions of time where you can see a pulse input of phosphate way upstream by Lake Winnebago, and see it as it progresses downstream,” Zorn said.

Coming closer to estimating the total phosphorus that’s being input into the bay of Green Bay, and better understanding the movement of phosphorus in the water, are essential steps in combatting this form of nutrient pollution.

J. Val Klump of the University of Wisconsin-Milwaukee and Kevin Fermanich of UW-Green Bay are co-principal investigators on this project, and Paul Baumgart of UW-Green Bay is assisting with the modeling efforts.

In addition, Paul Reneau of the USGS in Madison helped set up the remote capabilities for downloading data.  That was especially helpful since researchers did not have to travel to the sensor near ThedaCare except when a problem with the equipment was suspected.

While Erica Meulemans has presented some of the team’s preliminary findings on the Green Bay campus, there is still some statistical and other work to be done, says Zorn, anticipating further presentation or publication as more pieces come together.

For questions about this research, contact Michael Zorn at zornm@uwgb.edu.