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.
Click "source" to read the entire article.