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Elizabeth McCarthy/MEDILL

NOAA researchers collect zooplankton samples at night in Lake Michigan to measure of the health of the food chain. The organisms are sensitive to light, but not at the red wavelength.

Pollution, low water levels plague Great Lakes: Climate change to worsen the woes

by Elizabeth McCarthy
Dec 05, 2013


Elizabeth McCarthy/MEDILL

Crew member Bob Harvey keeps the deck of the Laurentian organized as scientific instruments are collected from Lake Michigan after a research trip.


Elizabeth McCarthy/MEDILL

Researcher Aaron Dunnuck prepares a canister to collect water samples from Lake Michigan.


Elizabeth McCarthy/MEDILL

Dunnuck and Jeff Elliott, NOAA researcher, lift a bottom tripod onto the boat. The black instrument is a transmissiometer, used to measure water transparency, which monitors them how much suspended sediment is in the water.


Elizabeth McCarthy/MEDILL

Elliott and other researchers rely on instruments such as an acoustic Doppler current profiler. The instrument sat on the bottom of the lake measuring currents throughout the water column by emitting sound waves, which are reflected by particles suspended in the water. The white plate at the top is the sensor head, and the blue cylinders are battery packs.

On a chilly and overcast day this fall, an 80-foot research ship set sail on Lake Michigan. It cruised the lake for nearly 12 hours, plying the dark waters well into the night, as temperatures dropped into the 30s and winds picked up speed.

The previous day had been windier still, with waters too rough for the crew to get much work done. They came back to shore early, exhausted and seasick, knowing the next day would be a long one. Science can be hard work.

The good ship Laurentian, one of the National Oceanic and Atmospheric Administration’s Great Lakes research vessels, sails as part of a monitoring program at NOAA’s Great Lakes Environmental Research Laboratory. The crew was headed out to continue field research on physical and biological characteristics of Lake Michigan.

The Great Lakes encompass the largest surface area of freshwater on Earth.

“When it comes to fresh surface water, nothing else comes close to what the Great Lakes have,” said Drew Gronewold, a NOAA hydrologist.

They are also beginning to feel the effects of climate change. And that has big consequences for the plants and animals that live in the lake, the communities that border the lake, and the people and companies who count on the lake for their livelihoods, recreation and contact with nature.

According to NOAA, about 65 million pounds of fish are harvested from the lakes every year, contributing about $1 billion to the Great Lakes economy. The Great Lakes also serve as a major thoroughfare for shipping.

But climate change threatens to change everything.

“Every day we hear from coastal communities and our constituents who are being personally affected by climate disruption and climate change,” said Angela Larsen, coastal program manager at Alliance for the Great Lakes, a Chicago-based nonprofit.

“Many of the Great Lakes coastal resources and the local economies that depend on them are really at risk due to climate change.”

Larsen said her organization is particularly concerned about the periods of both drought and heavy rainfall characteristic of climate change, and lake levels, near record lows, which could result from a variety of factors in addition to climate change.

Heavy rainfall is a problem because of the pollution that washes into lakes when urban areas flood. Chicago’s combined sewage overflows – runoff from sewer systems that collect a mix of rainwater, sewage and industrial wastewater - are diverted into Lake Michigan during floods, carrying bacteria, toxic materials and land-based debris. This runoff, combined with warming lake waters, can present health risks for swimmers and ideal conditions for harmful algae growth, Larsen said.

“All of this negatively impacts streams, fish habitat, and the local economies that depend on these recreational dollars,” she said.

A 2013 report by the National Wildlife Federation highlights the major problem of harmful algae blooms on Lake Erie, a lake nearly destroyed by pollution by the 1970s as the environmental movement kicked into high gear.

With 70 percent of the Lake Erie land basin used for agricultural purposes, according to the Ohio Department of Natural Resources, runoff often includes fertilizer and livestock waste, which greatly add to the nutrient load in the lake. This mix of nutrients and warm waters spurs algae growth,  exacerbated by zebra and quagga mussels – invasive species that have changed the fundamental ecology of all the Great Lakes. The newest threat may be a fish native to Central and Western Europe - the Eurasian Ruffe – according to research from the Nature Conservancy, the University of Notre Dame and Central Michigan University.

Lake Erie shares the algae growth struggle with the waters around Green Bay. Larsen said land use is a big driver of specific pollution problems in different parts of the lakes.

But low water levels threatening lakes Michigan, Huron and Superior in recent years, are driven not by land use but largely by changes in precipitation and evaporation. Lakes Michigan and Huron hit historic lows in January of 2013, after an unusually warm and dry 2012. NOAA projects they will remain about 16 inches below average for at least the next six months.

Determining how much water levels are driven by climate change versus other factors is extremely difficult for scientists. “When we look at projections of climate and propagate climate changes into water levels, we see a broad range of variability that reflects our uncertainty of what those climate patterns will be,” Gronewold said.

Illinois state climatologist Jim Angel explained that climate change could bring periods of both drought and heavy rains to the Great Lakes region, and that warm temperatures could mean more evaporation off the lakes. The lakes have particularly high rates of evaporation in the winter when the water is relatively warm and the air is dry and cold, he said. Warmer winters also mean less ice cover.

“Ice plays an incredibly important role in the water budget and in evaporation,” Gronewold said. It is thought that greater ice cover reduces the amount of water that escapes from the lake due to evaporation, but Gronewold said new research is showing this may not hold true, and that warmer waters in the fall may be driving winter evaporation.

The NOAA researchers on the Laurentian are also trying to find some patterns in the complex and ever-changing system of the Great Lakes. On the boat that day, Jeff Elliott and Aaron Dunnuck were retrieving scientific instruments and collecting water samples as part of a program looking at ecosystem dynamics through long-term biological monitoring and, more recently, physical modeling of characteristics of the lake.

Steve Pothoven, a fishery biologist with NOAA explained that they are studying the lower food web, which includes algae, plankton and nutrients, to understand the impacts Great Lakes stressors, such as invasive species. Climate change plays a role as well, but it’s difficult to parse out its precise impacts.

“Climate is always in the background,” Pothoven said, “But there are lots of other factors, too.”

Physical modeling helps provide context for the biological data, explained Nathan Hawley, a physical oceanographer with NOAA who will analyze the data collected from the instruments that were in the lake from early May to late October.

Hawley will look at variables such as water temperature, turbidity – or water transparency, and currents, which are all measured numerous times at multiple depths by the instruments over their six months in the lake. When Pothoven and other researchers see anomalies, this physical data could provide clues to help them understand what’s going on.

“They can correlate their sample with the conditions at that particular depth at that particular point in time. What they don’t know is how typical those conditions are over the short time period,” Hawley said. “One of the reasons for making these time series measurements is to get a handle on that short term variability so they can help to explain their data.”

But this kind of research is tough work. Elliott and Dunnuck, along with Andrew Yagiela, captain of the Laurentian, and Bob Harvey, crew member, stayed out on the lake until nearly midnight collecting water and zooplankton samples and retrieving instruments. The grueling field research continued as wind speeds soared and temperatures dropped.

And not only is the work physically demanding, but it requires a lot of expensive equipment, numerous trips to monitor and clean that equipment, a big boat and a decent sized crew, Hawley said. It’s a lot to ask of a government program with limited funding. And once the data is collected, it’ll take Hawley months to analyze it.

All this data is critical not only to understand the ecology and hydrology of the lakes, but also to communicate the changes and trends to major industries such as fishing, recreation, and commercial shipping, which is particularly affected by low water levels.

“A lot of times with low water levels, the big commercial freighters we see on the Great Lakes are forced to light load, meaning they aren’t putting the full capacity of whatever commodity they’re shipping,” said Keith Kompoltowicz, watershed hydrology chief at the U.S. Army Corps of Engineers.

“That in turn means they have to make more trips, which costs the shipping company more money, and that extra costs has to get passed on somewhere – and that’s usually to the consumer.”

While there’s little anyone can do about water levels and warming temperatures, better land use practices can help reduce the effects of heavy rainfall associated with climate change.

“The good news is that there are solutions that are available, and best management practices that are available to really help mitigate the risks and to modify the way we currently use the land both for agricultural and urban uses,” said Larsen. For example, planting more trees in cities can help absorb stormwater and reduce runoff, in addition to providing a myriad of other benefits.

“There are practices out there that can be relatively easily adopted to help mitigate these risks and help mitigate the damage.”