Researchers Explain Reasons Behind Record-Breaking Algal Bloom in Lake Erie

The algal bloom in 2011 in Lake Erie was due to a "perfect storm" created by high rainfall, warm climate and a high influx of nutrients from chemical fertilizers, according to a new study. Researchers warn that the conditions that led to this massive algal growth still exist and that we may see another such algal bloom in the future.

Algal bloom is mainly triggered when there are optimum factors for growth, like availability of nutrients and warm climate. The influx of nitrogen and phosphorus from fertilizers aids algal growth in a freshwater lake. The increased nutrient levels coupled with warm weather lets algae grow unchecked. When these algae die, other microbes begin to thrive on the dead algae and use up all oxygen in the water; preventing aquatic organisms from surviving.

"The factors that led to this explosion of algal blooms are all related to humans and our interaction with the environment," said Bruce Hamilton, program director at the National Science Foundation (NSF). "Population growth, changes in agricultural practices and climate change are all part of the equation. These findings show us where we need to focus our attention in the future."

The study was based on data obtained from satellite-based observations of the lake and computer simulations that track the algal bloom.

The algal bloom began in the lake's Western region in mid-July and spread to an area of 230 square miles, according to a news release from the National Science Foundation.

By October, the algal bloom had covered more than 1,930 square miles. The intensity of this bloom was about three times higher than any other algal bloom.

Researchers found that use of fertilizers, warm weather and nutrient run-off due to excessive rains in the region contributed to the massive bloom in algal population.

In May 2010, the region received 6.5 inches of rainfall, which is about 75 percent higher than the average rainfall of the previous 20 years.

"The 'perfect storm' of weather events and agricultural practices that occurred in 2011 is unfortunately consistent with ongoing trends," said Anna Michalak, scientist at the Carnegie Institution for Science's Department of Global Ecology and lead author of the study. "That means that more huge algal blooms can be expected in the future, unless a scientifically-guided management plan is implemented for the region."

A recent EPA survey had found that over half of the rivers in the U.S. can't support marine life due to low oxygen levels. The survey had found that 27 percent of all rivers in the nation have high amounts of nitrogen levels and about 40 percent have high phosphorous levels.

The present study is published in the journal Proceedings of the National Academy of Sciences (PNAS).