For Immediate Release
Date: November 29, 2023


Dave Neils
(603) 271-8865

NHDES Releases State Cyanobacteria Plan

Concord, NH - An effort to control cyanobacteria blooms in New Hampshire’s inland surface waters should include reducing nutrient inputs, enhancing lake management programs, and increasing public awareness and bloom monitoring, according to a new state cyanobacteria plan that the New Hampshire Department of Environmental Services submitted to the state Legislature on October 31.

New Hampshire’s Cyanobacteria Plan: A Statewide Strategy” covers a 10-year timeframe and documents the impacts of cyanobacteria and status of activities that address it. NHDES was directed to develop the plan in House Bill 1066, passed in 2022, with the primary goal of preventing the increase of, and eventually controlling, cyanobacteria blooms in New Hampshire’s waterbodies. The plan includes two additional goals: 1) to reduce the risk of cyanobacteria blooms to humans, pets and livestock; and 2) to better understand the causes of cyanobacteria blooms and develop methods to monitor their occurrence. People concerned about cyanobacteria blooms are urged to review the report for ways that they can take action. The plan was derived from input from the 17-member Cyanobacteria Advisory Committee, which represented diverse interest groups and NHDES staff experience. The committee reviewed existing literature and cyanobacteria-related data from New Hampshire’s surface waters to inform its work. 

Included in the plan are several key strategies and goals necessary to curb cyanobacteria blooms occurrences and risks, such as:

  • Implementation and support for policies and practices that reduce nutrient inputs to reduce bloom occurrences.
  • Enhanced lake management programs to diagnose blooms and support corrective actions that minimize their occurrence.
  • Increase public awareness for people who recreate in our water bodies to recognize cyanobacteria blooms and respond accordingly to minimize health risks.
  • Increase cyanobacteria bloom monitoring capacity to inform the public when and where blooms are occurring.
  • Prevent, detect and respond to cyanobacteria blooms in surface waters that serve as public drinking water supplies to minimize health risks to customers.

HB1066 provided $30,000 in funds to NHDES to complete this plan. The funds were used to complete a public outreach survey and research the prevalence of four cyanotoxins in samples collected in 2022. Both efforts informed the content of this plan and the future direction of managing cyanobacteria blooms in New Hampshire surface waters. Of nearly 700 responses to a public survey, 96% expressed concern over the impacts that cyanobacteria blooms have on the state’s surface waters including reduced recreational opportunities, health risks, and impacts to property values. Sixty-eight percent of samples from 2022 had detectable levels of a common cyanotoxin, microcystin and 20% of those samples exceeded the concentration considered safe for use as drinking water.

Since 2004, cyanobacteria blooms have been documented in 113 surface waters in New Hampshire and currently account for 64 water quality impairments. In 2023, 69 cyanobacteria warnings were issued statewide. Blooms are most frequent in the summer months but can occur year-round. Health risks associated with cyanobacteria are a result of the toxins (cyanotoxins) that they can produce. The toxins are known to cause a range of symptoms including, but not limited to, mild gastrointestinal illness or skin rashes to severe acute neurological system failures. The health risks associated with cyanobacteria blooms apply to humans, pets and livestock.

For more information, visit NHDES’ Healthy Swimming Mapper where known cyanobacteria blooms are reported weekly. Additionally, for those who are in and around New Hampshire’s waterbodies and observe a suspected cyanobacteria bloom, bloom reports can be sent to NHDES. NHDES urges lake users to perform visual assessments of the water before recreating and to stay out of the water and keep pets out if you can see any visual accumulation or coloration of the water. It is best to follow the saying, “When in Doubt, Stay Out.”

For more information on cyanobacteria and the state’s strategic plan, please contact David Neils, Chief Aquatic Biologist, at

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