Toxic Algal Blooms: A Growing Problem
The Prevalence of Phosphorus:
The year 2019 marked the 350th anniversary of the discovery of phosphorus (P) by the alchemist Hennig Brandt. Phosphorus is the foundation for all life on earth. It is essential to global food production and supporting population growth around the world.
In fact, it has been argued that phosphorus is at the heart of the food, water, and energy nexus. Over the past 75 years, agricultural demand has dramatically increased the rate of global phosphorus mobilization. However, our efforts to engineer systems that redistribute the world’s phosphorus stores have created unintended outcomes that are only recently being recognized.
Phosphorus is often in short supply in soil, and therefore is supplied by fertilizers, along with nitrogen. This use of fertilizer has greatly increased our capacity to supply food for the planet, but it has come at a cost. A recent study has revealed some inconvenient news about the phosphorus cycle, which explains how the essential element moves through the ecosystem.
The study concludes that human-dominated river basins may undergo a prolonged but finite accumulation phase when phosphorus inputs exceed agricultural demand, and this accumulated phosphorus may continue to mobilize long after inputs decline.
In other words, phosphorus accumulates in soil and in the water. Due to human activity, the phosphorus “cycle” becomes more like a one-way dead end.
Phosphorus inputs to agriculture initially increase soil fertility and crop yields, but continued phosphorus application in excess of plant uptake increases the risk of phosphorus loss from land to water bodies. Small amounts of phosphorus in water that drains from agricultural land can cause large problems with surface water quality. This is especially the case in freshwater systems, where the growth of algae is very sensitive to the concentration of phosphorus in the water.
Toxic Algae Blooms In the Great Lakes Region
Algae are natural components of marine and freshwater ecosystems and form the foundation of most aquatic food chains. However, harmful algae blooms (HABs) contain organisms that can severely lower oxygen levels in natural waters. Harmful algae blooms in freshwater lakes and rivers, or at estuaries, are caused by cyanobacteria, also known as “Bluegreen algae”. Some cyanobacteria can produce potent toxins known as cyanotoxins. Outbreaks of cyanobacteria that release toxins are commonly called “toxic algae” blooms.
Toxic algae blooms that can suffocate lakes and rivers have been, and continue to be a problem for the Great Lakes region which makes up the largest body of freshwater on Earth, accounting for one-fifth of the freshwater surface on the planet at 6 quadrillion gallons.
The Great Lakes Region has been affected by HABs over the past 60 years. In the 1960s and 1970s, water quality issues in the Great Lakes became a public concern. In particular, Lake Erie experienced significant eutrophication as a result of excessive inputs of phosphorus, and was perceived to be ‘dying’. This process is called cultural eutrophication.
In the years 2011, 2014, 2015, and most recently in July of 2019, substantial and deleterious algal blooms sparked major safety concerns from residents of the Great Lakes region. Lake Erie is the shallowest and most biologically productive of all the Great Lakes, meaning that it is the most sensitive to changes in nutrient levels, and thus has been the most severely impacted.
What’s the Big Deal?
Harmful algae blooms can affect human health and welfare. Excessive algae growth can degrade the quality of drinking water supplies. In recent years, toxic algae blooms involving a cyanotoxin called microcystin, have led to several temporary “do-not-drink” warnings around the Western Lake Erie Basin. Additionally, the toxins have serious environmental, economic, and social consequences for various industries including recreational tourism, boating, fishing, and hunting.
Algae blooms can also have a variety of direct damaging effects on aquatic ecosystems. The blooms result in a loss of water clarity, which suppresses the growth of aquatic plants, creating low-oxygen conditions that are fatal to fish and aquatic organisms.
So is there a cost to all of this? In short, yes.
Canadian citizens face a number of economic costs, both market and non-market, as a result of the blooms. Uncontrolled, algal blooms on Lake Erie could cost Canadians $5.3 billion over the next 30 years. However, if immediate action is taken to control the algae blooms, costs could be reduced by $2.8 billion.
Why is this happening?
Dissolved reactive phosphorus (DRP) from agricultural non-point sources is the primary driver of harmful algae outbreaks. Farmlands are categorized as non-point sources because there are no single entry points into the waterways.
Dissolved phosphorus poses a unique problem in the Great Lakes, specifically Lake Erie because it is more “bioavailable” to algae than particulate phosphorus. In other words, algae can easily consume dissolved phosphorus, leading to rapid algal growth. Since the mid-1990s the amounts or loads of dissolved phosphorus entering Lake Erie have more than doubled.
The impairment of surface water bodies by phosphorous remains a challenging, persistent, and widespread problem that threatens not only water quality but also water security.
There are 11 million people who rely on Lake Erie for clean drinking water. Harmful algae blooms pose serious risks for human health and the future sustainability of aquatic ecosystems.
A continued commitment to action is required over the next few decades to ensure the protection of the world’s largest freshwater resource. In order to protect our precious ecosystems, this would require the development and adoption of sustainable phosphorus conservation strategies coordinated across all sectors of the supply chain from producer to consumer, and to the postconsumer regarding issues of wastewater treatment. These strategies should be comprehensive and holistic, supporting agricultural production, improving water quality, and maintaining the ecosystem services provided across the watershed.