When Nutrients Overflow: Understanding Algal Blooms
Spring is full of yard waste, lawn fertilizer and rainfall. This combination, along with wastewater treatment effluent, can introduce excess nutrients to our streams and lakes.
When conditions include excess nutrients and temperatures rise algae can flourish and lead to an algal bloom. Algae is present in our rivers and streams and is a part of a normal aquatic ecosystem. However when a bloom occurs it can deplete oxygen levels and cause fish kills.
These blooms are common in shallow water where water temperature is warmest. Some types of algae can produce harmful toxins that can make people sick including Dinoflagellates, Diatoms, and Cyanobacteria (not actually a true algae). In freshwater systems the main concern is Cyanobacteria. Cyanobacteria can be present in a waterbody and not be a problem. But when their numbers increase during a bloom they can in some circumstances produce enough cyanotoxins to become a risk to humans and animals. Cyanobacteria do not always produce toxins and it is not well understood the reasons they do produce them. The toxins produced by Cyanobacteria have been detected in Jordan Lake but not at concerning levels. That being said, if you see discolored water that is green, blue green, reddish brown, or looks like spilled paint stay out of the water. North Carolina warns citizens that “when in doubt stay out.”
