July 17, 2012
A University of Wisconsin-Madison-led research team, funded by the Sea Grant Institute, is testing and refining an autonomous water-quality sampler, a device that could provide more accurate and timely diagnoses of an unwelcome rite of summer—toxic blue-green algae blooms that affect waters across Wisconsin.
Additionally, the scientists may be close to documenting a previously unrecognized role of nitrogen in supporting the toxic blooms.
Blue-green algae blooms are known as harmful algal blooms (HAB). They spring from the Cyanobacteria that are naturally present in state waters, but get active when water temperatures rise and plenty of sunshine is pounding down. The cycle generally picks up steam in mid to late July but due to the record high temperatures this year, the Wisconsin Department of Natural Resources has already issued a warning about contact with the pea-soup-like waters.
HABs pose a danger to the neurological systems or liver of humans, particularly children; pets, particularly dogs; livestock; and wildlife. The blooms can also kill pets, livestock and wildlife, including fish living in the toxic water.
“Now, public health officials just look at the water, and if it looks blue-green, they close a beach or post a warning near a waterway,” said Katherine McMahon, a UW-Madison microbiologist/engineer who is working with Ph.D. student Lucas Beversdorf on the project.
The payoff from the pair’s work is “a more-informed decision on beach closures,” McMahon said.
The decision about warnings and closings will be based on the powers of near-real-time sensors and samplers, “which look at the physics and biology of a lake, because those change all the time, even when we are not out collecting samples manually,” McMahon said.
The automated sampler is a small cone-shaped collection device standing about a foot tall and sprouting flexible tubes connected to filter-topped sampling bottles resting on rings of metal housing. Matthew Smith at the School of Freshwater Sciences at the University of Wisconsin-Milwaukee built the sensor that can be deployed atop a buoy launched on a lake or other waterway. The sensor will gather up to 26 samples, and can do so at various programmed times throughout a day.
McMahon said the benefit of an autonomous sampler is that a researcher, a resource manager or a public health official could never be out sampling every hour, and it’s important to do that because, “Bacterial communities on a lake change hour-to-hour around the clock. HABs can develop quickly and disappear by the next day.” With the new device, the sampling burden is lessened since it’s an autonomous process; the device is continuously collecting clues.
The autonomous device will preserve samples until the researcher can retrieve and test them, a process that can yield results in 24 hours or less, and speed public health warnings. The ultimate goal of the project is to develop robust detection methods that can be incorporated into the device, making it possible to detect bloom formation and toxicity in near-real time.
The project’s second preliminary finding regarding nitrogen could have larger implications for nutrient management. Now, nutrient-loading management sets targets mainly for phosphorus but nitrogen is another major component of fertilizers and goes virtually unaddressed.
Beversdorf said, “From a management standpoint, you can get rid of the phosphorus and then the nitrogen becomes more important. That could have profound effects on cyanobacterial populations. Does nitrogen regulate toxin productions? We know that some of the toxin molecules have lots of nitrogen in them. More nitrogen could lead to higher toxin concentrations.”
Through his data collection on Madison’s Lake Mendota for the last three years, he has noted a spike in the level of nitrogen just prior to widespread HABs.
Lake Mendota has been called the most-studied lake in the world. “Lake Mendota is a fantastic lake to study—its size, location—and it’s just eutrophic enough to make it a model system,” Beversdorf said, “And, we can extrapolate so much from its rich historical datasets.”
He concludes with a thought about the application of his work, “There’s a really important component that lakes play in a community that cannot be measured. You can’t do an economic assessment; you can’t put a price on the aesthetics. We might be studying microscopic things, but our findings relate to much bigger issues that are important to a lot of people here in Wisconsin.”