Harmful Algae Blooms Threaten Lake Erie
Satellite image shows the 2011 toxic algae bloom in Lake Erie. Photo courtesy of HealthyLakes.org
The World’s Largest Source of Freshwater
The Great Lakes contain the world’s largest supply of freshwater. In fact, according to NOAA’s Great Lakes Environmental Research Laboratory (GLERL), the Great Lakes contain 18% of the world’s supply of freshwater and 90% of all freshwater within the United States. They also provide drinking water for 40 million people. According to the EPA, Lake Erie alone provides drinking water for approximately eleven million people.
Human activities have had a detrimental effect on Lake Erie. A study by the U.S. Geological Survey (USGS) found that pesticide applications to crops in the Lake Erie-Lake Saint Clair Drainages are among the highest nationwide. Moreover, according to the Ohio EPA, 66% of the near-shore water in Lake Erie is nutrient impaired. Despite the extent of the pollution, however, its effects often remain largely unseen.
In recent years, however, the pollution problems in Lake Erie have taken on a much more visible form. In 2011, a toxic algae bloom spread across Lake Erie, coating the lake with a fluorescent green scum.
Lake Erie, 2011. Photo courtesy of HealthyLakes.org
According to the Healing Our Waters Great Lakes Coalition (HOW), the bloom covered 990 square miles of the Lake Erie—10 percent of the lake’s surface area. These blooms pose a threat both to the lake itself and to human health.
The Problem
Harmful Algal Blooms (HABs)
Harmful algal blooms (HABs) are excessive growths of toxin-producing algae caused primarily by excess phosphorus in the water. When conditions (such as high levels of nutrients) cause algae to reproduce rapidly, the result is a dense population of algae known as a bloom. Although some blooms are harmless, others contain toxins, and are therefore considered “harmful” aglal blooms.
Lake Erie (Sept. 1, 2011). Photo courtesy of Peter Essick.
The 2011 bloom primarily consisted of the algae microcystis aeruginosa, which produces a liver toxin, called microcystin, that can be toxic to mammals.
Algae in Lake Erie’s Maumee Bay. (Photo courtesy of NWF/Lake Erie Waterkeeper)
HABs such as microcystis aeruginosa are poisonous to both humans and animals. Although this type of algae has not been linked to any human deaths in North America, fatalities have been reported in other parts of the world. Moreover, according to GLERL, these blooms have been known to cause flu-like symptoms in humans and death in pets:
Getting it on the skin may give people a rash, hives, or skin blisters (especially on the lips and under swimsuits). Inhaling water droplets from irrigation or water-related recreational activities can cause runny eyes and nose, a sore throat, asthma-like symptoms, or allergic reactions. Swallowing water that has toxins in it can cause: Acute, severe gastroenteritis (including diarrhea and vomiting).
Photo courtesy of EcoWatch.org
According to sampling done by NOAA’s Center of Excellence for Great Lakes and Human Health, Western Lake Erie contained more microcystin in the summer of 2011 than the World Health Organization recommends for safe recreation.
According to one Report, algal toxins have caused large numbers of deaths of whales, sea lions, dolphins, manatees, sea turtles, birds, and wild and cultured fish and invertebrates worldwide.
Dead Zones
In addition to their human health impacts, the blooms consume oxygen when they decay, creating “Dead Zones,” or low-oxygen areas where most aquatic organisms cannot survive. In the 1960s, Lake Erie was considered “dead” as a result of excessive algae growth and oxygen-depleting decay. In response, a variety of actions were taken to reduce phosphorus levels in the Lake. In 1972, the same year the CWA was enacted, the United States and Canada signed the Great Lakes Water Quality Agreement, which limited the amount of phosphorus that could be discharged from sewage-treatment plants and established a total phosphorous load limit for Lake Erie of 11,000 metric tons per annum (MTA). According to the Environment America Research and Policy Center, nutrient pollution in Lake Erie has created a dead zone that is now larger than the size of Connecticut.
Image courtesy of EPA.gov
However, although these efforts resulted in a decrease of phosphorous levels from the early 1980s through the mid-1990s, a Report by the Phosphorous Reduction Task force to the Great Lakes Commission found that levels steadily increased since the mid-1990s, and have “reached levels that occurred in the 1970s, before the initiation of phosphorus reduction efforts.”
The Culprit: Agricultural Runoff
According to the Ohio Lake Erie Phosphorus Task Force, the sources of phosphorus that contribute to HABs in Lake Erie include both “point” sources (such as wastewater treatment plants) and “nonpoint” sources (such as storm water runoff). However, the Task Force concluded that the majority of annual phosphorus loading into Lake Erie comes from agricultural runoff into the tributaries that drain to Lake Erie. This makes sense, given that 60‐80% of the land use in the western basin of Lake Erie is agricultural. In a book published jointly with the Government of Canada, the EPA explains that
Runoff of soil and fertilizer during a rain storm. Photo courtesy of USDA, Natural Resources Conservation Service.
Lake Erie is the smallest of the lakes in volume and is exposed to the greatest effects from urbanization and agriculture. Because of the fertile soils surrounding the lake, the area is intensively farmed. The lake receives runoff from the agricultural area of southwestern Ontario and parts of Ohio, Indiana and Michigan.
However, although experts generally agree that the leading cause of HABs is phosphorus runoff from farms, the current regulatory regime is entirely unequipped to address the problem. The CWA prohibits the discharge of any pollutant into the waters of the United States, including Lake Erie and its tributaries,without a permit. 33 U.S.C. § 301(a).
Heat map depicting phosphorus concentrations in Western Lake Erie. Photo courtesy of LakeScientist.com
However, although phosphorus is considered a pollutant, § 502(12) (broadly defining the term “pollutant”); 40 C.F.R. § 132, tbl.5 (listing phosphorous in the Great Lakes System as a pollutant subject to water quality requirements), the CWA only prohibits discharges from “point sources,” § 502(12), and “agricultural stormwater discharges and return flows from irrigated agriculture” are explicitly exempted from the Act’s definition of “point source.” § 502(14). Instead, the Act simply requires that states develop management programs that identify best management practices to reduce nonpoint sources of pollution. § 319. However, as Kilbert et al. explain, this requirement does little to protect Lake Erie. Because the federal government cannot force state compliance with these practices, such plans are essentially voluntarily.
The Future
Algae blooms in the Bering Sea off the coast of Alaska. Photo courtesy of SeaWiFS Project, NASA/Goddard Space Flight Center.
Many experts believe that climate change will increase phosphorus levels in Lake Erie. For example, in its 2012 Report, the Phosphorous Reduction Task Force explains that
[t]he environmental consequences of more intense rainfall, snowmelt and runoff from these storms include . . . increased runoff and flooding leading to increased nonpoint source pollution. In agricultural areas, the more intense runoff that occurs during larger storm events also has the ability to transport significant amounts of other materials applied to the soil surface, including fertilizers, pesticides, organic matter and other harmful items.
Algae blooms in the Celtic Sea. Photo courtesy of NASA’s SeaWiFS Project.
The link between nonpoint source pollution as a result of increased rainfall and phosphorous levels in Lake Erie is staggering. Annual phosphorus loads to the lake exceed the 11,000 MTA limit in years in which runoff is higher than average, and according to the USGS, this excess phosphorus in rainy years is believed to be a direct result of discharges from nonpoint sources.
Photo courtesy of EcoWatch.org
The enormous 2011 bloom, which was the largest Lake Erie has experienced in decades, occurred during one of the region’s wettest years on record. According to the 2012 Report, rainfall that year was approximately 50% higher than average. In 2012, on the other hand, there was a severe drought in the Lake Erie basin. There was also less runoff, lower phosphorus levels, and minimal growth of HABs – despite the fact that that point source discharges remained relatively constant during both years.
Because climate change is expected to increase water temperatures and cause more sever storms that facilitate the flow of phosphorus into the lake, experts predict that massive algae blooms, like the one in 2011, will occur more frequently.
Algae in Lake Chaohu, China. Photo courtesy of seawayblog.com
Moreover, the problem of algae blooms is not limited to Lake Erie – other water bodies in the U.S. and worldwide are threatened by excessive nutrients. According to USGS, “HABs are a global problem, and toxic freshwater and (or) marine algae have been implicated in human and animal illness and death in over 45 countries worldwide and in at least 27 U.S. States.”
Because they are the primary culprit, the greatest reductions of phosphorus must obviously come from agricultural practices. However, many experts believe that agricultural best management practices applied at the current scale will likely be insufficient to reduce phosphorous loads to the level necessary to prevent dead zones and harmful algae blooms.