Underwater Robot Labs Monitor Toxins
The labs have been deployed in Lake Erie, where blooms of toxic algae have made water undrinkable in past years.
Almost exactly three years ago, in August 2014, residents of Toledo, Ohio were told to immediately stop drinking their city water. The “do not drink” advisory lasted three days, and sent residents across state lines in search of bottled water. Nearly half a million people were affected.
The culprit? A blue-green algae called cyanobacteria in Lake Erie, the city’s water supply. When conditions are right, cyanobacteria blooms into large, sludgy mats. These blooms can produce a toxin called microcystin, which causes a number of health effects in humans, ranging from rashes and diarrhea to liver damage. Due to climate change and human impacts like agricultural runoff, these toxic blooms are becoming more common.
“The problem is really worldwide,” says aquatic ecologist Tom Johengen, associate director of the Cooperative Institute for Great Lakes Research at the University of Michigan.
Johengen and his colleagues hope Lake Erie, one of the worst-affected lakes in America, may be one of the first to benefit from a new solution. They’re experimenting with a new technology – a lake-bottom “robotic lab” – to test water and give information and early warnings about pollution.
The technology is called an environmental sample processor, or ESP, and is positioned on the lake bottom four miles from the water intake for the Toledo municipal water supply. Looking rather like an industrial garbage compactor, the ESP is sometimes described as a "lab in a can." The fully automated ESP tests the water once or twice a day, and sends the results wirelessly to researchers.
This is much faster than the traditional process, which involves researchers traveling by boat to various locations, collecting, filtering and extracting watering samples, then analyzing them for toxins. That can take up to two days. And while water treatment plants monitor their supply for toxins as well, they test the water at the point of intake. This means if they find something, it’s already essentially inside the water treatment plant. The lab-in-a-can could give up to a day of warning about the approaching of algal toxins.
Lake Erie’s ESP is the first of its kind to be used in a freshwater system. There are similar labs off the coasts of Maine and Washington, as well as other locations, used mainly to monitor for toxins that might affect shellfish. Research from Stanford has shown ESPs can help give early warning to fishermen and recreational boaters in a saltwater setting, letting them know the water and fish within it might be contaminated. But as cyanobacteria blooms get worse, researchers say ESPs will likely become more common in freshwater.
Climate change is going to exacerbate the problem for two reasons, Johengen says. The first is warming waters. Cyanobacteria like warmth, and thrive in temperatures above 68 degrees Fahrenheit. Other algae prefer cooler temperatures, so when waters get warm enough, cyanobacteria begin to outcompete them and take over large areas. The second reason is runoff. Climate change alters weather patterns and produces more intense storms. Heavy rainfalls generate a lot of agricultural runoff, draining fertilizers from farms into the water supply. Cyanobacteria devour and thrive off these nutrients.
“The combination of warmer waters and high inputs from runoff can really spark these blooms,” Johengen says.
The researchers hope to use the ESP data in conjunction with computer models to understand exactly how the cyanobacteria blooms behave. They plan to track bloom movement both horizontally and vertically within the water, using information about currents and wind. This is important because the location and movement of a bloom can predict how it might affect humans. A surface bloom might only affect water recreation, meaning swimmers and boaters should be cautioned. But a bloom being driven deep by currents can affect water supply, as treatment plants generally intake their water from close to the bottom. Ultimately, the researchers hope to use the data to help prevent blooms as much as possible.
“Bloom eradication is likely never going to happen, but we can absolutely reduce the size and impact of these blooms,” says Tim Davis, an ecologist formerly of the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory.
The project, a collaboration between the Cooperative Institute for Great Lakes Research, NOAA's Great Lakes Environmental Research Laboratory in Ann Arbor, NOAA's National Centers for Coastal Ocean Science and the Monterey Bay Aquarium Research Institute, plans to bring two more ESPs to Lake Erie. Two will be deployed all the time, and a third can be rotated in on an as-needed basis.
The ESPs aren’t a “silver bullet,” Davis says. Researchers will still do weekly monitoring to get a greater variety of information about the water in multiple locations, not just where the ESP is deployed. But he and his colleagues believe similar technologies will become more common as they become smaller and cheaper. Right now an ESP weighs about 1,000 pounds and costs $375,000.
Some eleven million people live on the shores of Lake Erie, the shallowest and therefore warmest and most algae-prone of the Great Lakes. All stand to be affected by increasing toxic blooms. So do residents near many other American lakes, including enormous bodies of water such as Lake Okeechobee in Florida and Utah Lake, near Salt Lake City. Budget cuts and relaxation of environmental regulations under the current administration may scuttle plans for water cleanup, leaving lakes even more prone to toxins. With ESPs, perhaps residents may at least get a warning before the toxins arrive in their drinking water.