I recently wrote on the Erosion Control blog about the troubles facing Kansas farmers after this spring’s heavy rains washed away nutrient-rich topsoil. Topsoil is not only vital to crop health but also protects the land from erosion, and when it washes or blows away, it hurts a farmers’ bottom line. But if we follow that washed away soil off the farm and into rivers or oceans, we will find another problem—algae blooms and dead zones.
Phosphorus and nitrogen are key nutrients for plant growth, and as such, are common elements of fertilizer. But when fertilizer is washed into waterways, it contributes to algae overgrowths known as “algae blooms.” The most harmful are overgrowths of cyanobacteria, also known as blue-green algae, which produces a toxin called microcystin that can affect the liver and nervous system. When the algae die and decompose, the process consumes oxygen, meaning there is less for other marine life. Dead zones are areas in bodies of water where the oxygen levels are so low, marine life either dies or leaves. First comes the algae, and then the dead zone.
The appearance of a dead zone in the Gulf of Mexico has become an annual event. The National Oceanic and Atmospheric Administration (NOAA) has predicted that this year, due large part to “the abnormally high amount of spring rainfall in many parts of the Mississippi River watershed,” the dead zone will be roughly the size of Massachusetts. In the Gulf, algae growth is fed by both agricultural runoff and an influx of freshwater. NPR reports that in addition to helping the algae bloom, the change in salinity “has harmed a wide range of coastal animals that thrive in salty or brackish waters—including dozens of dolphins that were found dead.”
It’s not just marine life that’s affected. The same NPR article says the state of Mississippi has already closed 25 beaches along the Gulf Coast due to an overgrowth of blue-green algae. People can still visit the beaches, but should avoid any contact with the water, since microcystin can cause rashes, nausea and vomiting, diarrhea, and stomach cramps. Additionally, folks on the coast are advised not to eat seafood from the affected areas.
Heavy rain earlier this year has also led NOAA to predict a large blue-green algae overgrowth in Lake Erie. The lake provides drinking water to 11 million people, so the annual toxic algae blooms can have far-reaching impacts. In August of 2014, a bloom in the lake left residents of Toledo, OH, without access to clean tap water. According to an article in Mother Jones, “Back in August 2014, officials in the city of Toledo (population 400,000) had to warn residents for several days not to drink or even bathe babies in their tap water, which had gotten contaminated with microcystin drawn from the lake.” One year later, officials in Ohio, Michigan, and the Canadian province of Ontario, committed to reduce phosphorus runoff by 20% by 2020, a goal the Alliance for the Great Lakes says will likely not be met.
These annual algae blooms and the resultant dead zones in Lake Erie and the Gulf of Mexico have huge impacts, not only on the people who live near and rely on these bodies of water for their livelihoods, but on our ecosystem at large. The causes are complex—agricultural runoff, unusually heavy rainfall, sewage discharge—making simple solutions challenging. What steps would you like to see taken to reduce algae blooms? Send your thoughts and comments to [email protected].
