Wrentham warns: Toxic algae on Lake Pearl, water unsafe of people and pets

WRENTHAM -- A toxic algae bloom has developed on Lake Pearl, prompting the town to issue a town-wide warning Thursday afternoon that the 128-acre lake is unsafe for people and pets.

Specifically, residents and visitors are advised not to swim in the water, not to swallow the water, to keep pets away and to rinse off if they come in contact with the water.

The advisory was issued just past 2 p.m. Thursday, Oct. 22 and directed residents to the state website, www.mass.gov/dph/algae, for further information.

According to the selectmen's office, a resident brought the algae bloom to the attention of the Board of Health, which then informed the state Department of Public Health (DPH), and signs have been posted at the public access points to the lake.

DPH spokesman Omar Cabrera said the agency responded after the "potential bloom" at Lake Pearl was reported on Wednesday, Oct. 21.

"DPH was contacted by the Wrentham Board of Health (WBOH), and recommended that the WBOH issue a cyanobacteria advisory for Lake Pearl, a determination that was made following visual observations of the surface scum," Cabrera noted via an email, responding to questions from The Gazette/Wicked Local Wrentham.

The algal growth on the lake is what is referred to by scientists as Harmful Algal Bloom (HAB), or cyanoHAB on freshwater bodies.

It is not known how widespread the algae bloom is, or what area of the lake is most affected, but according to Cabrera, "the available evidence suggests that the risks are greatest when the level of certain cells, or the toxins they produce, reach certain levels."

"The goal of any water quality management plan is to take action before anyone becomes sick, before the safe levels are exceeded.  That’s why we recommend an advisory for the whole lake until the evidence of the bloom no longer exists," he noted. "Generally, if you are unsure if a bloom is present, you should avoid contact with the water - when in doubt, stay out!"

Presently, Cabrera noted, the DPH is aware of 29 CyanoHAB advisories at recreational water bodies in the state. Besides Lake Pearl, the nearest site that also has a bloom is Cabot Pond in Mansfield.

Among Wrentham's lakes, only Lake Pearl is affected, and there were no similar blooms reported on the lake over the summer.

"This is the first report to DPH of blooms like this at Lake Pearl (or neighboring Lake Archer)," Cabrera stated.

Earlier this summer, a suspected HAB bloom on Plainville's Lake Mirimichi prompted officials there to issue an advisory in Plainville and Foxborough (part of the lake is within Foxborough's border).

MORE ABOUT HARMFUL ALGAL BLOOMS

According to the Centers for Disease Control and Prevention, HABs “are the rapid growth of algae that can cause harm to animals, people, or the local ecology.”

The DPH notes on its website that "blooms can form when cyanobacteria, which are bacteria that grow in water, multiply quickly and form 'scums' or 'mats' on the surface of the water."

"Blooms can occur at any time, but most often occur in late summer or early fall," the DPH website states.

They are naturally occurring, but can be exacerbated by abundant nutrients -- often from septic systems and fertilizers -- in tandem with high water temperatures, and in some cases they can take over an entire pond system.

The DPH has been working with waterbody operators for more than 10 years "to evaluate and respond to reports of cyanobacteria (blue-green algae) at freshwater recreational waterbodies."

"Unlike typical fecal bacteria at waterbodies -- that can’t be seen with the naked eye -- algae blooms change the water’s appearance from slightly discolored to resembling a characteristic pea soup or thick paint. Blooms frequently appear blue or green but could be another color, such as brown or red," he said.

According to DPH, "most periodic blooms resolve themselves. Certain environmental conditions, such as slow moving water, warm weather, sunlight, and excess nutrients may all contribute to allowing these cyanobacteria grow faster (or 'bloom') and cause these surface water conditions."

"Generally the bloom will resolve itself when these environmental conditions change in a way that is 'unfavorable' to promoting the continued growth of these organisms," the DPH says -- for excample: Mixing of water from contributing streams, drop in air/water temperature, less sunlight, or the existing bloom consuming the available excess nutrients."

WHAT ARE THE HEALTH RISKS IF EXPOSED?

The most common types of cyanoHABs that bloom are Microcystis and Anabaena.

According to the DPH, "certain strains of Microcystis and Anabaena manufacture toxins called microcystin and anatoxin, respectively, and these toxins can produce adverse health effects. Toxins are released from intact cyanobacteria cells when they die in the water body or when they are ingested by animals or humans. Once ingested, the digestive juices destroy their cell wall (lyse the cell) and the toxin is released into the gastrointestinal tract."

The CDC notes on its website that HABs can "cause illness in people, companion animals (dogs, cats), livestock (sheep, cattle), and wildlife (including birds and mammals)."

"Exposures to the toxins can occur when people or animals have direct contact with contaminated water by: Swimming, breathing in aerosols (tiny airborne droplets or mist that contain toxins) from recreational activities, and swallowing toxins by drinking contaminated water or eating contaminated fish or shellfish," the CDC notes.

Symptoms vary, the CDC stated, "depending on how they were exposed, how long they were exposed, and the particular HAB toxin involved."

According to the CDC, "people or animals exposed to cyanotoxins through direct skin contact or inhalation may experience the following symptoms: Skin irritation, eye irritation, nose irritation, throat irritation, respiratory irritation.

For animals, reactions to exposure may be more severe, including: Excessive salivation, vomiting, fatigue, staggered walking, difficulty breathing, convulsions, liver failure, and even in some cases, death.

This article will be updated as more information becomes available. To read more from the CDC on this topic, visit www.cdc.gov/habs/illness.html