Green Without Envy: Great Lakes Drown in Excessive Nutrient Pollution

By Michael Mezzacapo, IJC

pointe pelee ontario lake erie algal bloom 2011
A photo taken off of Point Peele, Ontario, during 2011’s severe Lake Erie algal bloom. Credit: IJC

2017 was another significant year for algal blooms on Lake Erie, claiming the spot for the third largest algal bloom on record. Scientists believe the major factor of the massive bloom was due to excess runoff from agricultural areas due to high concentrations of phosphorus in the Maumee River watershed after heavy precipitation events in May and June. Excessive nutrient runoff from nonpoint sources is significantly degrading water quality in all the Great Lakes, with the exception of Lake Superior. Solutions to solving the excessive nutrient problem are complex and will involve widespread government, stakeholder and community participation.

The US National Oceanic and Atmospheric Administration (NOAA) recently highlighted an alarming figure: in eight of the last 10 years, Lake Erie has had algal blooms that were classified as significant. NOAA classifies severity based on a bloom’s biomass over a sustained period. But nutrients aren’t the only cause of the excessive algal blooms; other factors contributing to the increases include intensive land use practices and changing climate patterns.

chart western lake erie blooms
Chart showing the severity of western Lake Erie blooms. Credit: NOAA

Runoff from agricultural areas into western Lake Erie is the major source of nutrient loadings. Of the agricultural sources, about 70 percent of the nutrients are from commercial fertilizer application and 30 percent from animal manure. Combine excessive runoff of phosphorus from commercial fertilizer and animal manure with changing climatic conditions in the Great Lakes and you may have a recipe for excessive algal blooms and potentially harmful algal blooms (which emit toxins harmful to humans and wildlife).

loading to st clair western lake erie
Figure showing a comparison of total phosphorus (TP) tributary loading to Lake St. Clair and the western Lake Erie. Sources: Michigan Sea Grant, M. Maccoux, Contractor ECCC, S. Wortman, USEPA, D. Obenour, NCSU, M. Evans, USGS. Credit: IJC

Analysis from a recently released IJC Science Advisory Board Report showed that excess phosphorus from fertilizer application is often stored in agricultural soils, nearby ditches, buffer zones and wetlands with the potential to leach nutrients for years or even decades. “Even a small ‘leakage’ of excess phosphorus may be sufficient to contribute to algal blooms,” the report says.

(See also: “Less Fertilizer, More Transparency Needed in Western Lake Erie Basin”)

Want to Know More?
In addition to the IJC’s recent recommendations on nutrients in its TAP report, The IJC’s Water Quality Board and Science Advisory boards have released reports relating to the issue of nutrient pollution by highlighting watershed management tactics and investigating fertilizer loading issues. Click the reports below to learn more.
1. Fertilizer Application Patterns and Trends and Their Implications for Water Quality in the Western Lake Erie Basin. This report assesses fertilizer (primarily commercial fertilizer and manure) application and impacts in the western Lake Erie basin.
2. Watershed Management of Nutrients in Lake Erie. This report provides recommendations on how watershed management plans should be used to curb nutrient pollution in Lake Erie.
3. Evaluating Watershed Management Plans, Nutrient Management Approaches in the Lake Erie Basin and Key Locations Outside of the Lake Erie Basin. This report discusses watershed management plans to manage nutrient pollution in Lake Erie and identifies several key factors necessary for watershed management plans to achieve meaningful nutrient load reductions.

Eliminating all nutrient runoff isn’t the answer to solving this crisis. Just like the human body, lakes need nutrients to sustain life. Nutrients are chemical elements that support all animal and plant life. Nutrients support algae (technically known as phytoplankton), the primary producers which are the foundation of a lake’s food web. Eutrophication is the process a waterbody undergoes when subjected to an excessive load of nutrients. Eutrophication can set the stage for algae and aquatic plants to grow out of control. When the excess algae growth eventually dies, bacteria and microorganisms feed on the dead material and consume available oxygen in the water. If oxygen levels dip too low, massive fish die-offs can occur, which can severely impact ecosystems.

phosphorus cycle graphic ecosystem
A graphic illustrating the nutrient cycling of phosphorus in an ecosystem. Credit: Michael Mezzacapo

Excessive nutrient runoff also has the potential to impact conditions in and around the lakes and may affect human health. Research has shown that pathogens from bacteria in the algal blooms can cause avian (bird) botulism, which thrives in nutrient-rich, low-oxygen conditions. As environmental conditions become more favorable for algae and bacteria, humans may be at risk from the prevalence of diseases by consuming affected animals and fish, or coming into contact with contaminated water or objects.  Additionally, if municipal drinking water systems aren’t prepared to handle many of the toxins produced by harmful algal blooms, access to clean water may be impaired, as happened in the 2014 Toledo, Ohio, water crisis.

(See also: “Beach Read: Cyanotoxins in the Great Lakes”)

The impacts of excessive nutrients and algal blooms are being felt across the Great Lakes basin as well as other waters in Canada and the United States. Governments are taking notice. Through the Great Lakes Water Quality Agreement, the United States and Canada have established updated targets for reducing phosphorus loading to the western and central basins of Lake Erie. Strategies, known as Domestic Action Plans, outline programs and policies considered necessary to meet reductions in nutrient loading.

Updated targets include a 40 percent reduction in nutrient offloading between the US and Canada, especially in particularly sensitive tributary regions of Lake Erie, like Thames River in Ontario and the Maumee in Ohio.

The 40 percent reduction target commits Canada to offloading no more than 212 metric tons annually, largely from the Thames River and Leamington area. American emissions, centered on the Maumee and Sandusky watersheds, cannot total more than 3,316 metric tons to hit a 6,000-metric-ton target.

In its First Triannual Assessment of Progress (TAP), the IJC forwarded several recommendations to reduce nutrient pollution and improve water quality, urging the governments to provide more details on timelines, responsible parties and measurable outcomes.

nutrient pollution recommendations triennial assessment progress
A graphic outlining the IJC’s TAP recommendations to reduce excessive nutrient pollution in the Great Lakes. Credit: IJC

Although there are many non-regulatory or voluntary actions in place to reduce excessive nutrient runoff, such as agricultural best management practices (BMPs), the IJC has called for stricter standards and enforcement on nutrient runoff. Improving compliance on BMPs and using regulatory enforcement will assist the governments to meet set targets for nutrient reduction in Lake Erie.

Western Lake Erie water quality has been greatly impacted by nuisance and harmful algal blooms, but there is hope. In the 1960s and 1970s, phosphorus pollution from municipal wastewater systems and detergents was causing excessive algal blooms. Governments at federal, state and provincial, and local levels as well as citizens worked together to install pollution controls and substantially reduce the algal blooms, voluntary bans on phosphorus detergent began in the 1990s. Bold action solved the problem in the past and bold action is needed now. Many new research studies and reports address the issue of nutrient pollution, but this should not delay stakeholders from performing early measures to reduce their share of nutrient runoff.

Michael Mezzacapo is the 2017-2018 Michigan Sea Grant Fellow at the IJC’s Great Lakes Regional Office in Windsor, Ontario.

How Do Mussels and Nutrient Runoff Impact Lake Michigan’s Food Web?

By Kevin Bunch, IJC

quagga mussels
Quagga mussels have effectively displaced their fellow invasive species the zebra mussel throughout the Great Lakes, and can survive in cooler, deeper water than their counterparts. Credit: US Geological Survey

Scientists have known since the 1972 Great Lakes Water Quality Agreement that nutrient runoff from fertilizer and wastewater is responsible for harmful algal blooms. They’re also aware that invasive quagga mussels are to blame for changes in how nutrients move around the lakes and its food web. Now a recent modeling study has better defined the role quagga mussels play in the use and movement of nutrients within Lake Michigan, which could assist efforts to reduce blooms throughout the Great Lakes.

Quagga mussels are a dreissenid species native to the Ponto-Caspian region of eastern Europe that most likely entered the lakes through ballast water in the 1980s. The tiny creatures form hard shells and latch onto practically any hard surface before filter feeding out plankton in the water column. The mussels thrive in nearshore regions, with quagga mussels outcompeting their fellow invasive zebra mussels in many areas. Quagga mussels also are capable of surviving in deeper water than zebra mussels, pushing the invasion further offshore.

Lake Michigan has seen a decline in offshore primary productivity – essentially the rate of how organisms at the base of the food web convert sunlight and nutrients into biomass energy – for around the past decade, according to Darren Pilcher, research scientist with the Joint Institute for the Study of the Atmosphere and Ocean at the US National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory. Since these phytoplankton species are eaten by a wide variety of other creatures, including invertebrates and eventually fish, understanding what’s driving that decline is important, he said. There are two major drivers that have been suggested: the decline of nutrient pollution into the lake from runoff since the GLWQA went into force and the growth of the quagga mussel population.

“These mussels are able to just graze and eat the phytoplankton as they grow, and that’s one mechanism showing how productivity has been reduced in the lake,” Pilcher said.

The model Pilcher and his partners built shows representations of the lake’s productivity under different conditions. Researchers can see what the lake would look like with a reduced number of mussels, or with a reduced amount of nutrient runoff (based on the observed decline going back to before the mussels invaded). This allows them to tease out the effect of each process. The model accounts for how water moves throughout the lake and for its ecosystem, particularly phytoplankton and zooplankton – organisms that eat phytoplankton.

Pilcher said they found that the growth of the quagga mussel population and drops in total nutrient runoff have impacted the lake, but at different times and places. Quagga mussels have the biggest impact in the spring and late autumn due to how the water moves within the lake, Pilcher said. The mussels live at the bottom of the lake, while phytoplankton tend to live in the upper layers to soak in the sun’s rays. During spring and late autumn those water layers tend to mix, bringing those plankton down to where the mussels can eat them. In the summer, the water layers stratify and rarely mix, denying quagga mussels that food source outside of the nearshore zone where waters are shallower. The researchers had hypothesized that would be the case, and with the modeling they were able to see how the quagga mussel’s seasonal dependence worked.

“The phytoplankton sit in the top layer (of water) and no mussels are grazing on them, so they’re able to continue as business as usual at that point,” Pilcher said.

Cladophora algae mats have surged in nearshore areas where phytoplankton isn’t available to use phosphorus runoff as a nutrient source into the Great Lakes. Credit: Wisconsin Sea Grant

However, since mussels in shallower nearshore zones can continue to feed on phytoplankton, they’re clarifying the water and leaving a niche for other algae and bacterial species to move in and use the phosphorus there to grow and expand into blooms. This also has the effect of shuffling nutrients predominantly to the nearshore zone and processing them into a more bioavailable form, in what’s called the nearshore nutrient shunt. Runoff can exacerbate that, and as a result the impact of the runoff is mostly seen in the summer, when harmful algal blooms can grow and species like Cladophora, a kind of algae that lives on the lake bottom, can spread into large mats.

Since those nutrients aren’t making it into the offshore zones in the first place, species in the deep water zones are still out of luck. Pilcher said that some fish in nearshore zones still can conceivably eat algae or the mussels, but those in the offshore regions have a harder time finding food unless they’re willing and able to venture closer to shore. This has been thought to be contributing to the population declines of several fish species in the Great Lakes, such as lake whitefish, as they struggle to find food where they live.

In the future, Pilcher said they’d like to see benthic algae such as Cladophora added to the models to better understand how the mussels are affecting their growth. With the mussels clearing out more desirable phytoplankton in nearshore regions, phosphorus is going unused by those species, giving undesirable algae and bacteria an opening to grow. This information could be helpful as the Great Lakes states and Ontario work on reducing phosphorus loading into the Great Lakes, particularly Lake Erie, by helping refine phosphorus loading targets and expectations. Pilcher added that models using similar parameters could be developed for the other four Great Lakes; they already exist to some degree for Lake Erie.

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.

Watching Algal Blooms from Space

By Kevin Bunch, IJC

saginaw bay harmful algal bloom nasa
A harmful algal bloom in Saginaw Bay as spotted from space by a NASA satellite. Credit: Jeff Schmaltz, MODIS Land Response Team, NASA

Scientists don’t need to be out on the water collecting jars of algae to help measure a bloom – they can do it from space, too.

A team of scientists was able to use historical data from NASA ocean color satellites to measure the extent of Great Lakes algal blooms back to 1997, even before satellites were actively collecting the data. Michigan Tech Research Institute Co-Director Robert Shuchman said they wanted to answer the question on whether or not harmful algal blooms, or HABs, were getting worse year-to-year, focusing primarily on three areas: the western basin of Lake Erie, Green Bay in Lake Michigan and Saginaw Bay in Lake Huron. Thanks to a grant through the Great Lakes Restoration Initiative, they were able to begin the project about five years ago.

Using the data as a “time machine,” Shuchman said they were able to figure out the average extent of the blooms each year in those three basins. They found that all three locations seemed to behave independently of each other, even though they have similar weather patterns and are relatively near each other. While the extent of algal blooms on Lake Erie has been generally increasing, especially since 2006, Saginaw Bay has been fluctuating year-to-year. Green Bay blooms also fluctuate based on runoff and air temperature in the basin.

Michael Sayers, the researcher in charge of the study, said the lack of perennial HAB trends in those two bays compared to Lake Erie is possibly due to land use and geography. The worst of Lake Erie’s algal blooms is due to agricultural nutrients getting into the Maumee River during the spring, which in turn deposits them into Lake Erie.

Sayers said around 70-80 percent of the Maumee watershed is agricultural. In contrast, the Saginaw River and Fox River watersheds are closer to 40 percent agricultural. They also seem to react differently to weather factors like temperature, precipitation and seasonal climate – leading Sayers to believe that these blooms are “locally controlled phenomena.” The US Department of Agriculture’s Natural Resource Conservation Service has held community outreach efforts and directed money to farmers in the Saginaw River system to work with local agricultural producers to reduce sediment getting into the Saginaw Bay, Sayers said, so local factors could be playing a role beyond the weather, such as Michigan’s phosphorus-reduction legislation.

By correlating the satellite data with “resuspension events” involving winds and waves, the researchers found that resuspension of phosphorus into the water column from bottom sediments also does not seem to be the same issue in Green Bay and Saginaw Bay as it is in western Lake Erie. Sayers said looking in the areas where the blooms pop up repeatedly, there were few events that could have caused resuspension. He hypothesized that Green Bay’s narrow and long morphology may help protect the waterway from winds strong enough to cause resuspension, where phosphorus that has settled into the lake floor is churned back up into the water, providing new fuel for algal blooms.

Using satellites allows researchers to see a long-term analysis of the lakes and the blooms, adding some extra information on the cause and effects of HABs. There are some limitations, though. Shuchman said the land adjacent to the narrow Green Bay has a tendency to form cloud cover early in the day that doesn’t always clear up by the time the satellite moves overhead, and extended periods of cloud cover over parts of the lakes effectively blind the satellites from seeing surface conditions. Shuchman said aircraft now fly over Lake Erie once a week during the July-September HAB season, which helps collect data when it’s too cloudy for satellites. In the next few years, he hopes to add lower-flying drones to monitor the lakes on particularly cloudy days.

This information can be helpful from a public health standpoint as well. The toxicity of harmful algal blooms can make humans sick if ingested and cause rashes if touched, while it can outright kill dogs and other animals. Shuchman said the data is already used by water treatment facilities to protect their intake systems, and natural resources departments in each state for public safety regarding fishing and other uses of the water.

nasa aqua satellite
NASA’s Aqua satellite, launched in 2002, is used to observe weather and climate patterns and trends — including algal blooms — alongside another satellite called Terra. Credit: NASA/JPL AIRS Project

Sayers said satellites currently in use are primarily sensitive to plant-like green algae, but going forward researchers should be able to collect what’s known as hyperspectral data that can delve deep into subtle color differences. This would allow them to identify specific phytoplankton species and types, including some blue-green colored cyanobacterial algae like those found in toxic HABs. Sayer said the information would be helpful for resource managers and stakeholders in these areas, to find out what kind of toxicity they can expect from a bloom for planning water treatment and usage advisories. Green algae and blue-green algae species are not closely related, but both use the “algae” name based on being aquatic and being able to manufacture their own food using sunlight and nutrients in the water.

“Field measurements have been going on for a long time, but HABs are a complex issue, and remote sensing has added some information on cause-and-effect of HABs,” Sayers said.

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

Eight Ways to Assess the Health of the Great Lakes

By Ankita Mandelia
Sea Grant Fellow
IJC Great Lakes Regional Office, Windsor, Ontario

To assess progress toward improving water quality, scientists use ecosystem indicators to measure whether things are getting better, worse, or staying the same.

The IJC’s Great Lakes Science Advisory Board is completing a process to identify a subset of 16 indicators that can be used to communicate progress toward improving the health of the Great Lakes. That list is pared down further to eight indicators – the fewest that tell us the most – that address biological, chemical and physical integrity:

Eight indicators Great Lakes Science Advisory Board

How can examining these indicators provide useful information on how the Great Lakes are doing?

Take, for example, chemicals of mutual concern in water. This indicator measures the concentrations of legacy chemicals such as polychlorinated biphenyl compounds (PCBs), mercury, and flame retardants.

Concentrations of these chemicals in water are measured at strategic locations on regular time intervals within the basin. From the measured data, trends and patterns can be determined; such as whether the presence of a chemical is increasing or decreasing over time; or if the chemical is more highly concentrated in the water closer to or further away from land.

These chemicals of mutual concern in water matter because their concentration can give us insight as to where chemicals in an ecosystem came from and where they are headed. Models can be used to help pinpoint if a particular chemical is coming into the lake from a local or a global source, which occurs when contaminants are transported through the atmosphere.

For example, in Lake Erie, we know that relatively local sources (tributaries) are responsible for much of the pollution in the lake. We know that Lake Superior tends to be affected more by global pollutants transported through the atmosphere. Models also can be used to estimate what chemical concentrations might be in endpoints such as drinking water and fish, which are consumed by humans and other animals. Ultimately, this information is useful for telling people if the lake (or areas of the lake) is safe for drinking, swimming, and fishing, and whether or not the status is improving over time.

Figures 1 and 2 provide information on mercury in the Great Lakes. Mercury is on the two governments’ proposed list of Chemicals of Mutual Concern. In the upper Great Lakes, the source of mercury is precipitation; in the lower lakes, the source of mercury is industrial activity and watershed runoff.

This is one example of the Board’s work on how to communicate the indicators of Great Lakes health. The Board’s report on this study will be available on the IJC website in the coming weeks.

The IJC’s role under the Great Lakes Water Quality Agreement is to analyze information provided by the governments, assess the effectiveness of programs in both countries and report on progress toward meeting the Agreement’s objectives.

mercury cycle
Figure 1. The mercury cycle. Credit: Biodiversity Research Institute; Great Lakes Commission; University of Wisconsin La Crosse


source contribution mercury great lakes sediment
Figure 2. Relative concentrations of mercury sources. Credit: USGS

See also:  16 Ways to Measure the Health of the Great Lakes