Cyanobacteria Monitoring Report 2023-2025
- Melissa Langley
- 4 hours ago
- 6 min read
Program Overview
Connecticut River Conservancy (CRC) began monitoring cyanobacteria in Hampshire County, Massachusetts in 2023 and has since increased the number of sample sites and sampling frequency. This program was started due to concern from community members about potential cyanobacteria blooms at existing aquatic invasive species removal sites. Monitoring as of June 2025 includes 13 sample locations at eight water bodies, and each site is monitored on a biweekly basis from May through October.
All results are emailed to interested stakeholders following sampling events. Additionally, town health departments are notified if a public water body tests positive for a bloom. CRC is not responsible for any cyanobacteria-related signage at water bodies and does not have the authority to enforce regulations regarding water usage. Please consult with local town governments for issuing or lifting advisories related to cyanobacteria blooms and water usage.
What is Cyanobacteria?
Cyanobacteria is a phylum of photosynthetic bacteria that produce chlorophyll as well as another pigment called phycocyanin. Some cyanobacteria also produce cyanotoxins. Cyanotoxins can have a wide range of health effects on humans and animals dependent on species and concentration. A ‘bloom’ is said to occur when the ratio of chlorophyll to phycocyanin reaches a certain threshold. Anthropogenic climate change may increase the frequency and duration of blooms, and this may lead to increased health risks. The presence of a bloom does not necessarily indicate the presence of cyanotoxins, and additional testing is needed to determine the presence of toxins and the species of cyanobacteria present.
Different species may emit different toxins that are harmful at different concentrations and have different health impacts. Additionally, a cyanobacteria bloom does not always have a particular appearance, smell, or other indicator. As a result of these varied possibilities, it is best practice to avoid a water body with a confirmed or suspected cyanobacteria bloom.
Monitoring Results
This cyanobacteria monitoring project is still in its early phases, so the results presented below are not definitive. We now have data from two complete monitoring seasons, 2024 and 2025. Both years were hot and dry, with drought conditions observed late in the season. Collecting data for complete seasons under a variety of conditions will help to build a more complete picture about each individual water body as well as any impacts that land use or mitigation strategies have on cyanobacteria blooms.
A total of 356 data observations were made across the three years and the various water bodies sampled: 2023 had 48 observations, 2024 had 143 observations, and 2025 had 165 observations. Based on the information collected, this program has grown substantially since the first year of data collection.
Data from these three years at the sites do not show any clear trends. This is a small-scale study in a limited geographic region and may not be representative of larger data trends. Temperature, eutrophication, and other factors impact the likelihood and frequency of blooms seen in recent years (WHOI 2019). Additionally, increasing reports may be indicative of increased bloom occurrence, increased awareness of cyanobacteria blooms, and/or increased reporting capacity.
Blooms Detected by Site and Year
In 2023, blooms were only detected in Swimming Pond and Kayak Pond. In 2024, blooms were detected in Swimming Pond, Kayak Pond, Lower Great Pond, Triangle Pond, Rubber Thread Pond, and at Pine Island Lake (sampling location 1). In 2025, blooms were detected at Swimming Pond, Kayak Pond, and at all three sampling locations on Nashawannuck Pond.
In the figures below, blooms by sampling site are shown in green (bloom detected) vs. blue (bloom not detected).
Blooms Detected by Month and Year
In 2023, blooms were only detected in July and August. In 2024, blooms were detected in July, September, and October. In 2025, blooms were detected in June, July, and August.
In the figures below, blooms by month are shown in green (bloom detected) vs. blue (bloom not detected).
Data by Site Group and Land Use
Hockanum Road Ponds
The Hockanum Road Ponds group is comprised of two small ponds on private property in Hadley called Kayak Pond and Swimming Pond (named by the landowner). This is the smallest watershed in the project at 0.11 square miles. Due to its small size, the entirety of the watershed is considered forested by the National Land Cover Database (NLCD). At a finer resolution than we can calculate, there is some development (housing) and open green space (lawn) within the watershed.
Lake Warner
Lake Warner is an impoundment near the mouth of the Mill River in Hadley. It is the largest watershed in this project at 31.7 square miles. The Mill River watershed has a large variety of land uses. In addition to a significant amount of forest, primarily in the headwaters, it also includes significant agricultural use, and most of the University of Massachusetts Amherst campus. Lake Warner is preserved by the nonprofit Friends of Lake Warner and the Mill River.
Great Pond
Great Pond, located in Hatfield, is divided into two sections which we informally call “Upper Great Pond” and “Lower Great Pond.” Water flows out of lower Great Pond into Cow Bridge Brook and then into the Connecticut River. The 2.91 square mile watershed is primarily agricultural land use followed by wetlands and forests.
Northampton Ponds
Triangle Pond and Magnolia Pond are two hydrologically connected ponds just off the Oxbow and the Connecticut River within the Silvio O. Conte National Wildlife Refuge in Northampton. They are frequented by paddlers and anglers. This is a small watershed at 0.22 square miles that is split nearly equally between open water, wetland, and agricultural use.
Nashawannuck Pond
Nashawannuck Pond is in the center of Easthampton. It has a 10.2 square mile watershed which includes Rubber Thread Pond, and it is part of the Manhan River watershed. The watershed is about half forested and a little over a quarter developed. It is preserved by the Nashawannuck Pond Steering Committee, an all-volunteer group of Easthampton residents.
Rubber Thread Pond
Rubber Thread Pond is a small pond located to the west of Nashawannuck Pond in Easthampton. Its watershed is a 1.25 square mile subsection of the Nashawannuck Pond watershed. This portion of the watershed is nearly half developed and only about one-quarter forested. Compared to Nashawannuck Pond, Rubber Thread Pond is more immediately affected by urban runoff.
Pine Island Lake
Pine Island Lake is located in Westhampton, as part of the Manhan River watershed. It is within and has a small, mostly forested 0.72 square mile watershed. It is also within the Manhan River watershed. It is privately owned and preserved by the Pine Island Lake Association and has strict controls in place to prevent the introduction of invasive aquatic species.
Discussion
Factors impacting blooms include temperature, nutrient abundance (particularly phosphorus in freshwater systems), wind and weather, past and present land use, and more. Anthropogenic (human-caused) climate change exacerbates risk factors for cyanobacteria blooms. In particular, higher temperatures and increased nutrient inputs may contribute to trends in blooms. Land uses that contribute to higher nutrient inputs may generally pose greater risks for blooms; however, this does not appear to be the case at the locations tested.
A group of concerned community members organize barley straw deployment to help manage cyanobacteria blooms. Barley straw is being studied as a cyanobacteria bloom mitigation strategy that may reduce the time for which a bloom is present. As it decomposes, barley straw slowly releases a low dose of compounds (the exact chemical pathway is not entirely clear) that interrupt the reproductive cycle of the cyanobacteria. For this reason, barley straw is considered a bacteriostat as it does not kill the cyanobacteria.
Barley straw has been deployed in Nashawannuck Pond, Pine Island Lake, Hadley Swimming Pond, and Hadley Kayak Pond. The volume of barley straw deployed at each site has differed depending on the monitoring year but is generally calculated based on the surface area of the water body.
Overall, land use and barley straw presence do not show clear impacts on the presence of blooms. Hadley Kayak and Hadley Swimming Ponds have had blooms in each monitoring year, but the presence of blooms at other sites has differed year to year. More data is needed to better understand the factors contributing to blooms at these sites.
Cyanobacteria bloom at Hockanum Road Ponds in July 2025
Data use and next steps
CRC submitted all 2025 observations to the Environmental Protection Agency’s water quality database (WQX) in December 2025. This data is now available to the public through the EPA’s water quality portal. These data are preapproved by the EPA due to CRC’s Quality Assurance Project Plan (QAPP) designed for this monitoring project.
CRC plans to continue cyanobacteria monitoring at the same sites from May-October 2026 and, as of March 2026, has received funding from the Massachusetts Department of Environmental Protection (MassDEP) for the 2026 season to continue this work.
A note from Melissa (Water Quality Program Manager) and Jodie (Water Quality Monitoring Assistant)
We had a blast this year out on the water! We spotted whirligig beetles, water striders, great blue herons, double-crested cormorants, kingfishers, a green heron, dozens of painted turtles and red eared sliders, eastern newts, frogs, grackles, ducks, bald eagles, dragonflies and damselflies (including a dragonfly larva clinging to a twig!), aquatic snails, and more! We both saw our first beaver paddling on Magnolia Pond, lots of bryozoan (a colonial invertebrate reminiscent of coral) that we were able to look at under a microscope, and a new-to-us insect called a woolly alder aphid. We are so grateful to everyone involved in this program and everyone who supports CRC. Most of all, we are grateful for our stunning watershed and the many creatures and treasures within it.
