Algae is a natural component of a pond ecosystem; however, excessive richness of nutrients ("eutrophication") can lead to an explosion of algae called an "algal bloom". Depending on which of the many possible species of algae are involved, the impacts of a bloom can range from aesthetic to a health risk.
Blue-green algae (cyanobacteria) is a species of significant concern because it can produce toxins that affect the liver, kidney and nervous system. (Cyanotoxins include microcystin and others.) Cyanobacteria are not true algae, but are bacteria that have a competitive advantage over algae species because they can "fix" nitrogen from the atmosphere and control their buoyancy to seek out water-column depths where nutrients are most abundant.
Savery Pond has experienced increasing occurrences of toxic cyanobacteria blooms, with public health advisories issued in 2011, 2014, 2015, 2016 and 2017. Public health advisories typically close down access to the pond for periods of 4-6 weeks during summer months.
During potentially toxic cyanobacteria blooms, the Massachusetts Department of Health and Human Services may issue a public health advisory warning people to stay out of the pond and keep their pets from drinking the water. Algal blooms can affect the ecological health of the pond, as decaying algae can deplete dissolved oxygen and impact aquatic species (e.g. "fish kills"). Algal blooms also affect our ability to recreate, enjoy the natural resource we value so dearly, and can impact property values for homeowners.
SPC attempts to keep those on our Savery Pond mailing list informed about algal blooms in process. You can also check on the Massachusetts Department of Health and Human Services Algae Information Page for cyanobacteria advisories, and for useful information to help assess algal issues and guide responses. Concerns regarding cyanobacteria blooms should be reported to the State Environmental Toxicology Program (please CC emails regarding cyanobacteria to SPC and to Kim Tower at the Town of Plymouth Department of Marine and Environmental Affairs).
Cyanobacteria blooms are driven by excessive nutrient availability. Phosphorus is typically the nutrient that limits cyanobacteria growth. Savery Pond monitoring has shown relatively high concentrations in the pond water, and has suggested that "legacy nutrients" bound to pond sediments are being released into the water column. Nutrient occurrences and sources are discussed on the water-quality page.
Public Health Advisory Notice
Current Risk of Algal Bloom