Death by Nutrients: Toxicity of Ammonia and Harmful Algal Bloom (HAB) Events

When we think of nitrogen in the context of toxicity, we have historically been concerned with direct toxicity of ammonia to aquatic organisms. Ammonia toxicity continues to be an issue of emerging concern in the U.S. The US Environmental Protection Agency (EPA) has developed new ammonia toxicity criteria that protect sensitive mussels and snails, some of which are covered under the Endangered Species Act. EPA expects states to adopt and enforce these criteria, which are more restrictive than the previous criteria, in NPDES permits where these species are present.

In addition, ammonia and other forms of nitrogen, along with phosphorus forms, may contribute to harmful algal bloom (HAB) events as nutrients. HAB events are of increasing concern in the U.S. because of the toxins that are produced by the algae and their increasing frequency and prevalence.

The webcast will provide background information on these topics, discuss how WEF members may be impacted, and advise on how to respond and prepare for new requirements that may emerge. 


  • Tom Dupuis, Water Group Manager, HDR
  • Erin Houghton, Water Resource Specialist, Green Bay Metropolitan Sewerage District
  • Dr. Hans Paerl, Professor of Marine and Environmental Science, University of North Carolina, Chapel Hill
  • Tad Slawecki, Senior Engineer, LimnoTech (Moderator) 

There will be up to 1.5 Professional Development Hours (PDHs) offered for this webcast. Please check with your state accreditation agency to determine if you qualify. The PDH instructions will be sent to all attendees 24 hours after the webcast has ended.