Lake Erie’s Record-Breaking Algae Bloom May Become the Norm
Lake Erie’s Record-Breaking Algae Bloom May Become the Norm
By Breanna Draxler | April 1, 2013 2:01 pm
In 2011, Lake Erie experienced the largest algae bloom in its recorded history. At its peak in October, the mat of green scum on the lake’s surface was nearly four inches thick and covered an area of almost 2,000 square miles. That’s three times larger than any other bloom in the lake, ever. Plus it was toxic. Now research shows that such an event may become increasingly common. Algae blooms result from an excess of nutrients like nitrogen and phosphorus in the water, which throw aquatic ecosystems out of whack. The algae feed off the nutrients and grow so thick that they block sunlight, preventing other plants from photosynthesizing. And as the algae die, bacteria consume copious amounts of oxygen to decompose them, killing fish and other animals in the process. When the nutrient-loading gets really bad, it can sometimes lead to hypoxic, low-oxygen conditions, resulting in ecological dead zones like the one in the Gulf of Mexico.
To make matters worse, certain strains of blue-green algae are toxic, which makes these blooms dangerous to more than just lake-dwelling life. In the case of the 2011 bloom in Lake Erie, the researchers determined that blue-green algae accounted for the majority of the bloom, and concentrations of the toxic stuff reached 4,500 μg/L, which is 225 times greater than the maximum that the World Health Organization recommends for water used for swimming and boating.
One of the major source of nutrient loading in lakes is agricultural runoff from within a lake’s watershed—the area of land which drains to the lake. After nutrient loading in Lake Erie and the rest of the Great Lakes got really bad in the 60s and 70s, the U.S. and Canadian governments implemented the Great Lakes Water Quality Agreement to reduce nutrient loading to these iconic bodies of freshwater. For the next few decades, the agreement showed promising results, but in the 90s the nutrient concentrations began to creep back up.
In the years leading up to the 2011 bloom, the number and size of farms in Lake Erie’s watershed didn’t really change much, so what caused the massive explosion of algae growth? Researchers say it’s a combination of how farmers apply their fertilizer, and changing climate conditions, according to the study they published today in the Proceedings of the National Academy of Science.
http://blogs.discovermagazine.com/d-brief/2013/04/01/lake-eries-record-breaking-algae-bloom-may-become-the-norm/
