Potentially harmful algae turning Lake Erie green

A potentially harmful phenomenon is making a resurgence this year, causing lakes to change color.

NASA recently released overhead images of western Lake Erie and nearby Lake St. Clair turning bright green as algae blooms begin to encroach upon the water.

In fact, the National Oceanic and Atmospheric Administration estimates that this year's concentration is expected to be about 8.7 on a 10-point severity scale, but could possibly reach up to 9.5.

A 10 was reached in 2011, the worse year for algae on record on Lake Erie.

Sunlight, warm temperatures, and high levels of nutrients are causing the intense growth.

Part of the problem is the high level of phosphorus that was added when heavy rains resulted in runoff from agriculture.

According to one expert, the dire forecast reflects "the urgent need to take action to address the problems caused by excessive amounts of nutrients from fertilizer, manure and sewage flowing into our lakes and streams."

High amounts of algae can threaten safe drinking water, close off swimming areas, and kill fish by absorbing the water's oxygen.

Images of Lake Erie's algae problem in 2014: