Cyanobacteria Harmful Algal Blooms

Conducting monitoring, public communication and educational outreach efforts.

Cyanobacteria are natural components of freshwater ecosystems but can grow out of control and form surface blooms. These blooms are variously referred to as cyanobacteria harmful algal blooms, CyanoHABs, or cyanobacteria blooms. Blooms can be toxic to pets, livestock, wildlife and people.” Cyanobacteria blooms can be toxic to pets, livestock, wildlife and people.

Cyanobacteria can produce cyanotoxins, which can cause both acute and chronic illnesses. Acute effects, such as skin and mucous membrane irritation, can occur after short-term exposure with water containing cyanotoxins. Chronic effects such as liver, kidney and central nervous system damage, can occur over a long period of time from ingesting water containing toxins over a long period of time.

Performing a self-risk assessment prior to recreating can keep you, your family and your pets safe. There are two steps to a self-risk assessment. First, visually evaluate the water prior to recreating, looking for any discoloration or unusual growth. Second, check our resources to stay informed about active blooms across the state.

Cyanobacteria Plan            Prevention and Remediation  

Report an Illness

If you or someone in your family (including pets) becomes ill or develops a rash after recreating at one of New Hampshire’s surface waters, you should first consult with your doctor. You can then submit a detailed report to help us track waterborne-related illnesses. You can also check out the Center for Disease Controls fact sheets about cyanotoxin exposure for health care providers and veterinarians.

Drinking Water Exposure

In response to the growing concern about the public health risks of cyanobacteria and the increase in reported bloom occurrences in New Hampshire waterbodies, NHDES Drinking Water Bureau now offers grants to help public water systems implement programs to monitor for potentially harmful cyanobacteria blooms. Additionally, NHDES’ CyanoHAB Response Protocol for Public Water Supplies provides guidance regarding how to respond should a bloom occur within a surface waterbody used as a public drinking water source. General information about cyanotoxins in public drinking water supplies can be found through the EPA.

Cyanobacteria Harmful Algal Bloom Program Manager