News from the New Hampshire Department of Environmental Services

DATE: 06/19/2020

State Issues Cyanobacteria Advisories and Alerts in New Hampshire

Concord, NH- Several cyanobacterial blooms have been observed in New Hampshire this month. “Cyanobacteria Advisories” are issued when samples are collected and identified, with cell concentrations exceeding the state threshold of 70,000 cells/ml. “Cyanobacteria Alerts” are shared when photos and reports have been submitted to NHDES (no samples have been collected or if blooms have already dissipated). Advisories and Alerts are not based on toxin evaluations and are intended as a precautionary measure. These messages are shared to inform the public to be on the lookout, and to be cautious in waterbodies with blooms.

One advisory is current:

Lake Winona, New Hampton/Center Harbor (Issued June19)

Five advisories have been issued and removed:

Baboosic Lake, Amherst/Merrimack (June 17 – June 19)

Silver Lake, Hollis (June 8 – June 19)

Millville Lake, Salem (June 3 - June 10)

Clough Pond, Loudon (June 2 - June 10)

Governors Lake, Raymond (May 27 - June 10)

There have also been several other bloom sightings, and alerts have been shared amongst the communities. These blooms have been reported, but either dissipated quickly, or did not have concentrations exceeding 70,000 cells/ml.

Blooms observed/Alerts:

Baboosic Lake, Amherst/Merrimack

Lees Pond, Moultonborough

Goose Pond, Canaan/Hanover

Locke Lake, Barnstead

Phillips Pond, Sandown

Mascoma Lake, Enfield

Island Pond, Stoddard

Lake Winnepocket, Webster

Learn more about Harmful Cyanobacterial Blooms and Advisories in New Hampshire:

Cyanobacteria Facts

Is that cyanobacteria? Maybe it is green filamentous algae?

NH Cyanobacteria and Beach Bacteria Advisories

Cyanobacteria Press Releases

Blooms may appear blue-green, but also display a variety of colors as it grows and decays, or when mixed with other debris such as pollen or other phytoplankton. These organisms are suspended throughout the water column, but often get caught at the surface or shorelines during rapid growth. The blooms typically move around the lake which is sometimes driven by lake currents and prevailing winds. The conditions may rapidly change at your individual shorelines. As the bloom dies, you may also see white clouds near shorelines of the lake. Be cautious of lake water that has a surface scum, changes colors, or appears to have green streaks or blue-green flecks aggregating along the shore.

Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells and released upon cell death. Toxins can cause both acute and chronic health effects that range in severity. Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage.

Please report a bloom to NHDES 

603-848-8094 or

NHDES cannot get to all locations as blooms happen. While we DO NOT encourage making contact with a bloom, some volunteers do deliver samples to NHDES for free analyses of identification, concentrations and limited cyanotoxin testing. Photos are the best way to share your findings and really help us evaluate the immediate conditions. Review instructions below.

Sample Drop-off Hours & instructions

Monday through Friday: 8:00am – 3:00pm

Please first call 603-848-8094 if you have a cyanobacteria sample to drop off.

Coordinate sample drop-off with the Cyanobacteria Program coordinator, Amanda McQuaid.

Sample instructions

Take a photo and record locations (coordinates or address if possible).

Share photos with the Harmful Algal and Cyanobacterial Bloom Program.

text (603-848-8094) or email (

If sampling,

Wear gloves and mask.

Dip a glass or hard plastic bottle through the bloom.

Cap the bottles and rinse off with freshwater to remove bloom material from the bottle’s exterior.

Label bottle(s) with contact info, water body, town, location, time, weather or other notes if applicable.

Transport sample(s) immediately or place on ice until drop-off (within 24 hours).

Transport to 29 Hazen Drive, Concord at main entrance.

Text 603-848-8094 to confirm drop off occurred.

If you notice anything resembling cyanobacteria, please refrain from recreating in bloom water and DO NOT drink the water. Keep pets and children out of the water and contact NHDES immediately. Call NHDES to report a cyanobacteria bloom at (603) 848-8094 or email