Sea Lamprey: The Greatest Invasive Control Success Story

By Kevin Bunch, IJC

sea lamprey
Sea lampreys are among the oldest invaders of the Great Lakes. Credit: C. Krueger, GLFC

An invader in a massive freshwater basin. An uncountable number of spawning grounds. A fishery on the brink. A desperate search for a solution that ended up becoming the most successful aquatic invasive species control team effort in American and Canadian history. It’s not a movie, but rather the true tale of the sea lamprey’s invasion of the Great Lakes.

The sea lamprey is parasitic fish native to the Atlantic Ocean. As an adult, it latches onto other fish with its suction cup-like mouth, using a rasping tongue to cut into its victim to suck out bodily fluids and blood. In the Atlantic it doesn’t typically kill its hosts, but the fish in the Great Lakes have no such luck. It’s estimated that a single lamprey can destroy an average of 18 kilograms (39 pounds) of fish in its parasitic lifetime, with only about one in seven fish surviving a lamprey attack. It’s not to be confused with native lamprey, which are smaller and have different coloration, and don’t usually kill the host fish.

Sea lampreys were first detected in Lake Ontario in 1835. While there has been discussion on whether it is native to Lake Ontario, it most likely is an invasive species that entered through the Erie Canal, according to Marc Gaden, communications director for the Great Lakes Fishery Commission (GLFC), a binational organization funded by the Canadian and US governments. The 1919 reconstruction of the Welland Canal, which bypasses Niagara Falls to connect Lake Ontario to Lake Erie, likely allowed the sea lamprey to enter Lake Erie and on to the rest of the basin. They were discovered in Lake Erie in 1921, Lake Michigan in 1936, Lake Huron in 1937 and Lake Superior in 1939. The sea lamprey found an immense number of tributaries featuring the combination of rocky nesting grounds to lay eggs and silt for larval lampreys to grow in, making the Great Lakes a lamprey Eden. In its native habitat, the sea lamprey spends most of its life in saltwater, making it the rare species that has adapted to living entirely in freshwater systems like the Great Lakes, similar to the Pacific salmon species introduced to control invasive alewives.

lake trout lamprey
A Lake Trout caught in Lake Huron with a sea lamprey attached. Credit: Marc Gaden, GLFC

The impact on the Great Lakes fishery was devastating. Prior to the invasion, about 20 million pounds or about 9 million kilograms of fish were harvested commercially each year in the upper Great Lakes – Superior, Huron and Michigan. By the 1960s that amount was reduced to about 300,000 pounds (136,077 kg) per year, while sea lamprey were killing close to 100 million pounds (45.4 million kg) of fish each year, and 85 percent of the remaining fish were scarred with lamprey attack wounds.

“Commercial fishermen and fishery managers first realized they had a problem around 1940, when it became clear what was happening to the Huron-Michigan fisheries from lamprey,” Gaden said. “That’s when the managers and scientists went into high gear and started seeking control measures.”

With little experience with aquatic invasive species, a wide variety of control methods were attempted. These methods included physical barriers to keep lamprey from entering the streams they use to spawn, crude electrical barriers to block their advances and sieves to stop larvae from eventually entering the Great Lakes from those inland streams. Entrepreneurs tried to make sea lamprey a commercially fished species for human consumption, but none of these attempts worked in stopping the sea lamprey.

The breakthrough came after years of searching for a chemical compound that would kill sea lamprey and not harm other organisms. A compound called TFM was discovered and field-tested in 1957, and entered management usage in 1958 through the binational GLFC. It has been used to great success.

The lampricide targets larval sea lampreys living in streams. After hatching from eggs found upstream in rocky areas, larvae make their way to silty areas and burrow into the substrate until they emerge as adults. The lampricide kills them in that weak, larval state by disrupting their metabolism before they can ever grow up to become the top predator in the Great Lakes. After decades of use, Gaden said the sea lamprey population in the Great Lakes has been reduced by about 90-95 percent from their peak in the late 1950s, and dropped the amount of fish killed by the lamprey to about 10 million pounds (4.5 million kg) a year. While it also affects native lamprey species, sea lamprey larvae tend to live and spawn in different areas from the native species; fishery managers focus on those stream areas where sea lamprey larvae burrow to minimize the impact on native species.

larvae
Dead sea lamprey larvae washed up on the shore of the Manistee River after a successful lampricide treatment. Credit: R. McDaniels, GLFC

Lampricide isn’t the only tool used to control lamprey numbers, Gaden said, as good pest control takes multiple tacks. Physical barriers are still in use to deny lampreys a path to their preferred spawning grounds. And if those lampreys can’t reach a place to spawn, there’s no need use lampricide treatments, which is expensive and time-consuming. The GLFC also deploys traps to catch lamprey entering or leaving the streams to remove them from the system, and has tested sterilizing male lamprey in the St. Marys River to try and overwhelm the number of fertile males. Most recently, Gaden said the GLFC “is on the cusp” of using isolated lamprey pheromones to affect their behavior – drawing lamprey away from ideal spawning locations and toward traps.

“We’re working on unlocking their genome,” Gaden said. “There are things within the lamprey genome we can exploit, like create conditions so they only produce males, but that’s further into the future.”

Mark Burrows, physical scientist and project manager in the IJC’s Great Lakes Regional Office, said the GFLC has sponsored important research devoted to controlling and eradicating sea lampreys while protecting native species, much of which was highlighted at the recent International Association for Great Lakes Research conference in Detroit.

“They deserve a lot of praise for the progress they have made in combatting this destructive invasive species, and I look forward to the GLFC forging another 10-fold decrease in lamprey numbers at some point in the future,” Burrows said.

While a focused and targeted approach to invasive species can work in smaller inland lakes, the size of the Great Lakes makes controlling aquatic invaders difficult. That they invaded a waterway that also serves as a border between Canada and the United States added an additional wrinkle. It meant both countries needed to work together, even though fishery management is primarily the domain of state, province, tribal and First Nation governments. This team effort has kept sea lamprey from completely dominating the ecosystem of the Great Lakes for decades.

lamprey traps
Sea lamprey traps are being tested in the field, set up in the Ocqueoc River in Michigan. Credit: T. Lawrence, GLFC

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

 

Invasive Mussels Turning Central Lakes into a Food Desert

By Kevin Bunch, IJC

invasive mussels nutrients
Invasive mussels have caused nutrients such as phosphorus in the Great Lakes to clump closer to the shorelines. Coupled with mussels’ tendency to clarify water, this has led to an expansion of the algae Cladophora. Credit: USGS

Invasive zebra and quagga mussels are taking nutrients that would otherwise be in deeper waters and shunting them closer to the shore, which could make it more difficult to halt harmful algal blooms.

Known as the “nearshore nutrient shunt,” this migration of phosphorus and other nutrients used as food by plankton has led to some severe negative impacts in the existing Great Lakes food web. Algae, particularly Cladophora which grows on the hard surfaces near the mussels and feeds on the nutrients the mussels excrete, are thriving in those nearshore regions where nutrients are stockpiling.

The shift in nutrient locations also has benefitted other species that prefer nearshore and benthic – or lake floor – environments, according to Dr. Harvey Bootsma, associate professor in the School of Freshwater Sciences at the University of Wisconsin-Milwaukee.

Historically, a greater chunk of phosphorus entering the lakes has found its way offshore, where it serves as food to phytoplankton. Those in turn are eaten by zooplankton, and fish can feed on both types of plankton, as well as other aquatic species that eat them. Some phosphorus ends up finding its way into the benthic level, periodically getting kicked back up dissolved into the water, where it can continue to serve as fertilizer for phytoplankton.

With invasive mussels, more phosphorus is staying in the nearshore environment, cycling through and never making it into deeper waters. Nearshore currents also tend to keep dissolved phosphorus in the water column, where Cladophora gets the first crack at this food supply. Coupled with the mussels’ voracious appetites clarifying the water column, this can lead to greater harmful algal growth, resulting in the blooms seen on Lake Erie and in bays throughout the Great Lakes. The mussels also are capable of scavenging offshore plankton as it drifts into the nearshore zone, ultimately retaining the nutrients from the plankton in the mussels’ nearshore home.

zebra quagga mussels
The zebra mussel, left, and quagga mussel, right, are a pair of invasive species originally from Europe that have dramatically altered the Great Lakes food web. Credit: NOAA

The impact this has had on the food web is significant. Some species of fish that historically have lived offshore or in the water column are willing to enter nearshore or benthic regions for food. Round goby, an invasive fish that feeds on the mussels and other invertebrates, has a ready food source in the nearshore region. This has led to some native predatory fish, like the brown trout, steelhead trout and Atlantic salmon, venturing into the nearshore areas to feed on the gobies. Other species, such as Chinook salmon and coho salmon, don’t feed on round gobies and aren’t making that move into the nearshore. Instead, their food supply is declining as the offshore plankton production is limited by the mussels, and their populations are suffering.

The expanded Cladophora mats could be causing other problems too. Bootsma said studies have shown Cladophora can harbor higher concentrations of bacteria as it decomposes on beaches. In northern Lake Michigan there have been an increasing number of birds killed by avian botulism. Bootsma said there is evidence suggesting the Cladophora could be promoting growth of the bacteria that cause botulism. When round gobies end up eating the toxic bacteria and in turn get eaten by birds, the birds get sick and die.

This nutrient shunt has led researchers to conclude that more stringent controls on the amount of phosphorus and other nutrients making it into the Great Lakes are needed to improve water quality. While mussels are the primary culprit behind the resurgence of Cladophora, on Lake Erie it’s believed this is why harmful algal blooms and other water quality issues associated with excessive nutrients rebounded in the 1990s, despite existing regulations of phosphorus and other nutrients, and have continued to plague the lake in the decades since.

The United States and Canada have agreed to reduce phosphorus entering Lake Erie by 40 percent of 2008 runoff amounts, though neither government has unveiled its plan yet. Bootsma said based on historical data and numerical models, that reduction amount should be enough to reduce the problems of toxic algae and deep-water hypoxia – the formation of oxygen-deprived zones in the water – to acceptable levels. The IJC recommended similar reduction amounts in a 2014 report released as part of the Lake Erie Ecosystem Priority.

While reduced phosphorus loading may help to address phytoplankton blooms in Lake Erie, Bootsma said there’s still uncertainty as to how nearshore Cladophora growth will respond to a reduction in phosphorus entering the water. Lake Michigan, with its lower phosphorus concentration compared to Lake Erie, still has problems with the nearshore algae. This is leading scientists to question whether localized phosphorus reductions will impede Cladophora growth or if phosphorus concentrations in the entire lake need to come down first. Lower phosphorus concentrations in the offshore areas could further reduce the amount of plankton in those areas, hurting the food web in those areas even more than the mussels already have.

“What we need now is models, based on solid research, that tell us how both the offshore and the nearshore zones will respond to changes in phosphorus loading,” Bootsma said.

Great Lakes Water Levels Expected to Stay Above Long-Term Average

By Kevin Bunch, IJC

chicago coastline lake michigan
Extremely high water levels can cause erosion and increase flood risks in coastal areas, such as along the Chicago coastline off Lake Michigan. Levels are not expected to be high enough to significantly increase those risks in the coming months, however. Credit: L.S. Gerstner

Water levels on the Great Lakes are likely to remain above the long-term average through the spring and summer, according to forecasts assembled by the US National Oceanic and Atmospheric Administration, Fisheries and Oceans Canada, Environment and Climate Change Canada and the US Army Corps of Engineers. But none of the Great Lakes are expected to reach record high water levels set mostly in the 1980s or 1950s.

While each lake is unique, they all tend to follow a similar cycle based on seasonal changes. Water levels typically reach their seasonal low during the winter months before increasing in the spring due to snowmelt and precipitation. Water levels tend to peak during the summer months, before beginning to drop in the fall and early winter.

There are three main factors that impact lake water levels, said Drew Gronewold, physical scientist with NOAA’s Great Lakes Environmental Research Laboratory: the precipitation over the lakes, evaporation of water on the lakes into vapor, and the runoff that comes into the lakes.

These variables, in turn, are affected by changes in air and water temperatures. For example, Gronewold said the timing of big runoff pulses is dependent on the amount of snow building up in the winter months and when it melts in the spring.

A water level decline in the fall is generally driven by evaporation, as air temperatures drop while surface water temperatures are still relatively warm. While water temperatures were relatively warm during the fall and winter months of 2016-2017 – leading to a lack of ice cover – evaporation amounts have been typical for this time of year due to a relatively mild winter air temperatures, Gronewold said.

These recent conditions, coupled with historical data, lead agencies to expect the water level rise to remain fairly typical this spring and into the summer. As water levels are already above their long-term average for this time of year, researchers expect that they’ll remain above average in the coming months, Gronewold explained.

There is still plenty of uncertainty, he added, as the amount of snow on the ground is less than it has been in some recent winters. It’s also difficult to predict continental-wide meteorological and climate patterns that impact Great Lakes weather patterns and temperatures. These can range from an El Niño effect like the one seen in the winter of 2015-2016 or a “polar vortex” that hit the region in the winters of 2013-2014 and 2014-2015. This uncertainty is expressed as a range of possible water levels in the forecasts released by the US Army Corps and Fisheries and Oceans Canada.

Great Lakes water levels also can be influenced by human management. Hydropower plants and a gated dam on the St. Marys River are used to manage outflows from Lake Superior into Lake Michigan-Huron, while a hydropower plant on the St. Lawrence River is used to manage outflows from Lake Ontario. Outflows through these structures are managed binationally by boards and according to orders and criteria established by the IJC. Nonetheless, the control of water flows through these lakes is limited, and weather conditions and water supplies remain the most significant factor affecting water levels.

Water levels are measured based on the International Great Lakes Datum, defined as the height above sea level at Rimouski Quebec on the St. Lawrence River. Agencies have been measuring lake levels since the 1860s, with more reliable levels going back as far as 1918. They base the lakes’ long-term average water levels on that information.

“We expect a range of water level conditions depending on water supplies,” said Jacob Bruxer, senior water resources engineer with Environment and Climate Change Canada. “There’s a lot of variability and uncertainty in weather and water supply forecasts, particularly when looking beyond a few weeks’ time, so we don’t try to forecast any specific trends and instead consider a full range of water supply scenarios that could be expected.”

According to recent forecasts, through September 2017 Lake Superior is likely to remain at or above seasonal averages, with a small chance of falling below its long-term average in July. There is less uncertainty for the spring months; water levels were about 5.5 inches (0.14 meters) above the long-term average by the end of March, and by May that range could be between 2.7 inches to 10 inches above the average (0.07 meters to 0.27 meters). By September, water levels could be as high as 1 foot (0.3 meters) above the long-term monthly average for Superior.

low water levels grand traverse bay
Low water levels can limit boat access to the water – as seen with these docks off Grand Traverse Bay in Michigan – and cause shipping problems in the Great Lakes. Credit: Michigan Sea Grant

Lake Michigan-Huron, considered as one lake hydrologically, was about 9.4 inches (0.24 meters) above the March long-term average by the end of the month. By September, Michigan-Huron is expected to remain above the long-term average, in a range of 1-16 inches (0.02-0.4 meters). Gronewold said Michigan-Huron saw water levels fall slightly more during the fall months of 2016 than is typical, but that is unlikely to make a discernible difference during this spring and summer.

Higher-than-average water levels are anticipated on Lake Erie, which has seen water levels on the rise in recent months, reaching more than 17 inches (0.44 meters) above the long-term average by the end of March. Water levels are expected to continue to remain above average this spring, before starting to fall around June to a range of 3.9-16 inches above average (0.10-0.41 meters).

Lake Ontario has a slight chance of being just barely below its long-term average going into summer, but will more likely be above it by up to 15 inches (0.38 meters). The forecasted peak is in May, when water levels could be 3.9-21 inches above average (0.10-0.55 meters). Water levels are then expected to fall at about the same degree as they usually do, according to the long-term average.

The US Army Corps publishes 12-month forecasts for Lakes Erie, Huron-Michigan and Superior, as well as Lake St. Clair, based on current conditions and similar historical weather data. Uncertainty grows substantially more than six months out, but most outcomes for Lakes Erie and Michigan-Huron suggest a greater likelihood of continued higher-than-average water levels through the year. Lake Superior also has a better chance of higher-than-average water levels, but faces a substantial possibility of being below that long-term average, too.

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

Finding Inspiration on ‘Big Water’

By IJC staff

Great Lakes Watermarks are about inspiration. The two latest examples come from Katherine O’Reilly and John Kennedy.

O’Reilly, a graduate student at Notre Dame, talks about growing up near Lake Erie, “pea green water” and how she was moved to study coastal wetlands and their role in improving water quality.

Kennedy, of Green Bay, Wisconsin, says his interest in “big water” started as a child, on Lake Michigan. He’s spent decades working to solve water quality problems in Green Bay.

The IJC’s Great Lakes Watermark Project includes these and other watermarks in partnership with Lake Ontario Waterkeeper. We’ve been gathering and sharing stories about the freshwater seas since last year.

See a special Watermark Project website for more, including how to submit your own.

Scientific Institute of the Month: School of Freshwater Sciences

By Jeff Kart

The School of Freshwater Sciences at the University of Wisconsin-Milwaukee prides itself as the only graduate school in the North America solely dedicated to freshwater issues. For 50 years, it’s maintained the largest water-focused academic research institute on the Great Lakes.

“What sets us apart from your average school is that we tackle water from an interdisciplinary perspective,” says Eric Leaf, assistant dean for advancement. That means integrating a wide variety of scientific disciplines, as well as engineering, urban planning, policy and public health. “The networks of inputs (to the Great Lakes) is so complex that you need every discipline to understand it.”

Emily Tyner, a graduate student in the School of Freshwater Sciences, dives while working with the National Park Service to study benthic oxygen dynamics at Sleeping Bear Dunes National Lakeshore and how they may trigger avian botulism outbreaks. Credit: Harvey Bootsma/University of Wisconsin-Milwaukee
Emily Tyner, a graduate student in the School of Freshwater Sciences, dives while working with the National Park Service to study benthic oxygen dynamics at Sleeping Bear Dunes National Lakeshore and how they may trigger avian botulism outbreaks. Credit: Harvey Bootsma/University of Wisconsin-Milwaukee

The school is located in Milwaukee’s urban harbor near the shores of Lake Michigan, giving researchers and students a unique vantage point.

“It’s everything about our culture,” Leaf said. “We can walk out the back door, get on a boat and go do research.”

The Neeskay in the Milwaukee River. Credit: Troye Fox/University of Wisconsin-Milwaukee
The Neeskay in the Milwaukee River. Credit: Troye Fox/University of Wisconsin-Milwaukee

The school focuses on four areas: Ecosystem dynamics with an emphasis on large lakes, human and ecosystem health, water policy, and water technology. Overall, there are 120 people in the organization, including 20 faculty and senior scientists and 60 master’s and Ph.D. students. In addition, the school maintains close ties to water-focused groups in engineering, geosciences, atmospheric sciences, architecture, and urban planning at the University of Wisconsin-Milwaukee.

“Student success, research excellence and university engagement are the main themes of UWM,” Leaf said. “At the school I can’t separate those things. The students are working on real research projects that affect the community.”

The School of Freshwater Sciences was founded on the idea that policy decisions that affect the lakes should be driven by science. “That’s what our students are learning,” Leaf said, “how they as scientists can affect policy, how to communicate science and how to communicate with decision makers.”

The school operates a research vessel called the Neeskay — a named derived from a Ho-Chunk Native American word that means “pure, clean water.” Leaders are in the early stages of planning and fundraising for a next-generation ship that will operate as a research vessel and floating classroom.

See also: Milwaukee to Host Second Public Meeting on Progress to Restore Great Lakes

Students from the school conducting research on Lake Michigan aboard the Neeskay. Credit: Peter Jakubowksi/University of Wisconsin-Milwaukee
Students from the school conducting research on Lake Michigan aboard the Neeskay. Credit: Peter Jakubowksi/University of Wisconsin-Milwaukee

Since the Great Lakes are a shared resource with Canada, collaboration with agencies in that country also are routine — and valuable, says Associate Professor Harvey Bootsma.

Bootsma grew up in Canada and studied at the University of Manitoba and the University of Guelph. He conducts nearshore work related to problems like Cladophora, a type of algae that grows to nuisance levels, and invasive species like zebra and quagga mussels.

He says working with colleagues at the University of Waterloo has been especially helpful. Workshops between the Milwaukee school and the Ontario university have allowed scientists to compare notes and helped jumpstart several areas of research.

“We have similar problems in a number of the Great Lakes, especially nearshore issues,” Bootsma said. “It’s really beneficial for groups of scientists from different lakes to get together.”

What is the school trying to discover?

“It’s more of a lab-by-lab thing,” Leaf says. “From a broad perspective, the school wants to investigate how the Great Lakes and other water systems function—and how we as humans impact them—so that decision makers and managers can make informed decisions to manage our most precious water resources.”

That includes work such as developing a model of nutrient contamination to help water managers reduce the size and duration of “dead zones” in Green Bay.

“We do a tremendous amount of work collaborating with the community in southeast Wisconsin and around the Great Lakes,” Leaf said. “That’s one of the points we take pride in: Our work is not theoretical, it is applied science.”

Leaf notes a movement in Milwaukee to revitalize its inner harbor. The school recently received a grant to conduct an extensive aquatic survey of the harbor.

“In addition to revitalizing land use of the harbor and making it a stronger part of the community, (organizers) want a harbor that’s environmentally clean, that supports recreational fishing, that supports birds and wildlife, that becomes a natural refuge in the city,” he said.

School researchers are working with partners including the Harbor District Inc. and the Wisconsin Department of Natural Resources to assess existing fish forage and spawning habitat and develop a map to inform strategic development.

“It’s a really interesting project because it’s being done in Milwaukee but the way we’re doing it could theoretically be done in almost any harbor,” Leaf said. “It’s science to inform policy decisions and drive economic activity.”

Jeff Kart is executive editor of the IJC’s Great Lakes Connection and Water Matters newsletters.

Where are Water Levels Heading on the Great Lakes?

By Kevin Bunch, IJC

lake michigan beach water levels great lakes noaa
A Lake Michigan beach located near Frankfort, Michigan, in September 2015. Credit: NOAA

Forecasting agencies in the United States and Canada expect Great Lakes water levels to remain near or above their long-term average for the next six months.

Water levels are measured on the International Great Lakes Datum, defined as the height above sea level at Rimouski Quebec on the St. Lawrence River estuary. According to the coordinated, binational forecast at the beginning of July, Lake Superior is expected to remain about 6 inches, or 15.4 centimeters, above its long-term average for this time of year through the summer, before falling closer to average levels in the fall. While this forecast is based on normal weather conditions in coming months, lake levels could be higher or lower depending on whether we have a wetter or drier than normal summer and fall. Long-term averages are based on data going back to 1918.

Lake Michigan-Huron, which have a common level due to their connection at the Straits of Mackinac, is expected to be 10-12 inches (30.8 cm) above average in the summer before falling closer to average in the fall. Lake Erie also is expected to be within 1 foot above average in the summer before ending closer to 8 inches, or 20.32 cm, above average in the fall. Lake Ontario’s July level is 1 inch (2.54 cm) below average for this time of year and is expected to remain close to average in the fall.

Jacob Bruxer, Environment and Climate Change Canada senior water resources engineer, said Lake Ontario’s comparatively lower water levels are due to the warm, dry weather conditions around the lake that started around March. Bruxer is also a member of the IJC’s International Lake Superior Board of Control and the Great Lakes-St. Lawrence River Adaptive Management Committee.

“Those conditions would be bad if we started at average levels, but we’re right around average,” Bruxer said. “We’re not seeing any significant concerns to shipping or recreational boaters.”

The higher water levels on Superior, Michigan-Huron and Erie mean some boat launches could be underwater and beaches are smaller than they would be with lower levels. On the flip side, boaters should have plenty of depth to get their boats into their docks, and anglers may find more coastal areas to fish than they would otherwise. Bruxer added that high levels can lead to greater erosion along bluffs and shorelines due to waves and storms.

Drew Gronewold, a hydrologist at the Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan, explained that the Great Lakes typically follow a seasonal cycle where water levels rise in the spring from runoff and peak in early summer. The lakes then fall in the autumn and winter months as evaporation — caused by temperature differences between the warm water and cool air — picks up, reaching their lowest point around January and February.

As of mid-July, Gronewold said there’s no indication that the autumn dip will be stronger than usual in the lakes, or that water levels will increase – something that occurred in the autumn and winters of 2013 and 2014 on Lake Michigan-Huron and Lake Superior. Bruxer said the lakes are expected to remain either near or slightly above seasonal averages for the foreseeable future.

Coordinated six-month forecasts of Great Lakes water levels are published online each month by the US Army Corps of Engineers and Environment and Climate Change Canada (via the Canadian Hydrographic Service). The US National Oceanic and Atmospheric Administration (NOAA) also provides these forecasts on its water level online viewer each month. Forecasted water levels are determined using binational data and several different models that account for possible variations in evaporation, precipitation and runoff on the lakes over the coming months.

While forecasts are typically only for a six-month period, the Army Corps of Engineers has recently developed a 12-month probability outlook.

Lauren Fry, civil engineer with the Corps, said the model provides potential outcomes given climatic scenarios, developed based on current conditions and similar existing historical weather data. For example, with the strong El Niño cycling over the past winter, Fry said the agency used data from  similarly strong 1982 and 1997 El Niño events to determine a range of potential lake level impacts from October 2015 until September 2016. The most recent one-year outlook from April suggests higher-than-average water levels will most likely continue until April 2017.

water levels measured feet meters great lakes michigan huron graph
Water levels are measured in feet or meters above sea level, with data compiled by US and Canadian organizations. The green line represents forecasted water levels, while the red line indicates recorded points for Lakes Michigan and Huron as of June 30. Credit: US Army Corps of Engineers

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

 

Nitrogen Pollution Concerns in Great Lakes Coastal Wetlands

By Matthew Cooper, Northland College

 When it comes to nutrient loading to the Great Lakes, it’s usually phosphorus that makes headlines. The algal blooms that plague western Lake Erie and the “dead zone” that forms in Green Bay, for example, are linked to excessive phosphorus runoff from agricultural and urban lands. However, our study recently published in the journal Freshwater Science suggests that at least one important Great Lakes habitat may be affected by nitrogen loading just as much as it is by phosphorus.

Coastal wetlands of the Laurentian Great Lakes are critical habitats for many ecologically and economically important plants and animals. And like the rest of the Great Lakes, these habitats are susceptible to nutrient pollution from sources such as agricultural and urban runoff as well as discharges from sewage treatment facilities. Yet, there has been very little research devoted to understanding how coastal wetlands in the Great Lakes actually respond to nitrogen and phosphorus pollution.

To shed some light on this question, we conducted experiments to simulate various nutrient pollution scenarios by adding combinations of nitrogen and phosphorus to small areas (called benthic substrates) within each wetland. We then measured how the algae on these substrates grew in response to the added nutrients. While the simulations were conducted at a small scale within each wetland, they revealed a lot about how these wetland ecosystems might respond to nutrient loading.

algal growth
Experimental nutrient additions. Each round disk is a surface that is treated with a nutrient combination (either nitrogen, phosphorus, a combination of nitrogen and phosphorus, or a control that does not contain nutrients). Algal growth is measured on each disk after three weeks. Credit: Jessica Kosiara

After analyzing results from 54 wetlands of lakes Michigan and Huron we found that nitrogen, not phosphorus, had the greatest effect on wetland algal growth. Forty-three percent of the wetlands tested exhibited a response to the nitrogen treatment alone and an additional 18 percent exhibited a response to nitrogen if phosphorus also was provided. Just two wetlands showed a response to phosphorus alone (36 percent did not respond to any of the nutrient treatments). This differs remarkably from other Great Lakes habitats where phosphorus loading tends to cause the greatest effect.

map great lakes coastal wetlands algae to nutrient additions
Results of experimental nutrient additions in 54 coastal wetlands. Red symbols indicate a response of algae to nitrogen additions, yellow indicates a response to both nitrogen and phosphorus, and blue indicates a response to phosphorus alone. The size of the symbol indicates the magnitude of the response. The largest responses tended to occur in northern wetlands, which were the most pristine wetlands. Credit: Freshwater Science

Perhaps the most interesting result of the study, however, was that the response to our experimental nitrogen additions was greatest in wetlands that were located in the most pristine areas, such as those along the northern shores of Lake Michigan and Lake Huron. The landscape in this region is predominantly forested with little agriculture or urban development. These include some of the highest quality and most “natural” wetlands in the region. Therefore, the response to experimental nitrogen additions in these wetlands demonstrates what appears to be their natural susceptibility to nitrogen loading. In contrast, wetlands that were surrounded by agricultural and developed lands, such as those in Saginaw Bay and southern Lake Michigan, showed much less response to the added nitrogen, presumably because these wetlands already receive a lot of nitrogen runoff from the landscape.

nutrient discs coastal wetland algal growth simulated
Nutrient disks after three weeks in a coastal wetland. The three cups on the left are controls (no nutrients added) and the three on the right contained added nitrogen. Algal growth was stimulated by the experimental addition of nitrogen. Credit: Jessica Kosiara

The types of algae growing within the wetlands also appeared to be affected by nitrogen loading. For example, algae that has special adaptations to allow them to utilize nitrogen from the atmosphere (called nitrogen-fixing algae) were most common in the most pristine wetlands and fewer of these specialized algae were found in the wetlands that receive nitrogen runoff from surrounding agricultural and urban lands. This supports our hypothesis that Great Lakes coastal wetlands are naturally sensitive to nitrogen loading and that nutrient pollution from the landscape can alter algal communities in these habitats.

Algae is an important energy source for much of the food web in Great Lakes coastal wetlands, so effects associated with nitrogen loading may have broad implications. For example, stimulation of excessive algal growth due to nitrogen loading may cause a buildup of organic matter as the algae grow, then die and accumulate on the sediment. As this organic matter decomposes, oxygen in the water is consumed, ultimately making the habitat less suitable for resident fish populations.

Currently, there is very little management focus on human-derived nitrogen loading to the Great Lakes. For example, the Great Lakes Water Quality Agreement between the United States and Canada to restore and protect the waters of the Great Lakes, includes specific phosphorus loading targets for each of the Great Lakes. The Agreement provides an essential framework for implementing programs to maintain or improve water quality. The Agreement does not, however, address nitrogen loading — and nitrogen concentrations continue to increase throughout the Great Lakes. The implications of this nitrogen buildup for the entire ecosystem remain unclear, though negative impacts to coastal wetlands appear to be one risk that warrants further investigation.

Matthew Cooper is from the Mary Griggs Burke Center for Freshwater Innovation at Northland College in Ashland, Wisconsin.