Harmful Algal Blooms (HABs)

Algae are natural and important to aquatic ecosystems (lakes, streams/rivers, estuaries, and the ocean). Under certain conditions, some species can produce toxins that affect human health and the environment.  Algae can grow in excess (blooms), leading to harmful impacts on the environment such as low/no oxygen (hypoxia/anoxia) or acidification (reduced pH levels in the water).  These blooms may affect human communities through unsightly conditions, toxins, or taste and odor issues that affect recreation, tourism, and drinking water.  Pets and livestock may also be affected.

 Algal growth leading to impacts on human health and the environment are referred to as Harmful Algal Blooms (HABs).  HABs can occur in all water types, and some can move with water flow.  In Louisiana, HABs most often concern a group of algae called cyanobacteria or blue-green algae.  These are present most often in fresh waters and in lower salinity estuarine waters.  These HABs are also known as HCBs or CyanoHABs, and can be present across the state at varying times of the year. Other types of HABs (for example red tide) may occur in more marine waters from time to time.

Information on HABs may be found here:

• U.S. Environmental Protection Agency (USEPA) Information on HABs
• USEPA How People and Animals Are exposed to HABs
• Centers for Disease Control Information on HABs 
• National Oceanic and Atmospheric Administration, National Centers for Coastal Ocean Science - Cyanobacteria Algal Bloom from Satellite in Lake Pontchartrain, LA for computer based satellite imagery of CyanoHABs (images current usually within a couple of days).
• U.S. Environmental Protection Agency CyAN app for cellphone based satellite imagery of CyanoHABs.
• *NEW* The USEPA and partners have developed a Freshwater HABs Forecast visual tool for the continental US.  Persons planning to recreate in or on the water may find forecasts (% likelihood of CyanoHAB) of many lakes and coastal areas across Louisiana.  The application takes time to load, and works best on computer/tablet.
• National Oceanic and Atmospheric Administration Information on HABs

When it comes to Harmful Algal Blooms --- When in Doubt, Stay Out!

 Date last updated: 04/10/2025