Shasta, a black Lab and retriever mix, splashed happily in Ashumet Pond for about a half-hour on Friday last week, October 2, as her owner, Carolyn Shepard, threw a toy into the water for her to retrieve.
Ms. Shepard returned to the pond with Shasta the next day but after about 15 minutes of playing fetch, another visitor to the pond notified Ms. Shepard of a health advisory warning of a cyanobacteria bloom in the pond.
Cyanobacteria, also known as blue-green algae, is potentially toxic.
“It was very scary,” Ms. Shepard said. “She was lucky that the toxins weren’t as concentrated in that area.”
Ms. Shepard rushed her 8-year-old dog back to her home in Plainville and bathed her to wash any lingering toxins from her fur.
After Shasta was clean Ms. Shepard brought her to Angell Animal Medical Center in Boston, where the dog received emergency treatment after veterinarians discovered elevated liver levels.
The veterinarians gave Shasta a pill to protect her liver and kept the dog on an IV overnight, Ms. Shepard said.
“She’s a super-sweet dog; she wants to be hugged all the time,” Ms. Shepard said. “I would have been devastated if I had lost her.”
Ms. Shepard said Shasta is doing well, but she also urged the towns of Mashpee and Falmouth to post signs warning of the health advisory more conspicuously.
“Please post it so people like me that are coming from out of town can actually see the signs and not put our dogs at risk,” she said. “If it was really bad, Shasta could have been dead within the hour.”
Richard H. York Jr., who retired from his position as Mashpee’s director of natural resources earlier this year but continues to do water quality monitoring as a volunteer, said it is possible the dog could have been exposed to cyanobacteria toxins.
“The symptoms are consistent with an algal toxin, but it’s not proven,” Mr. York said. “If the dog did get this from the pond, it could have kicked it up and swallowed a slug of concentrated cells.”
Shasta’s possible exposure to cyanobacteria toxins highlights the dangers of cyanobacteria, which has been known to kill pets and cause liver damage and other complications in humans.
This summer three ponds in Mashpee had health advisories posted that warned of the potentially toxic algae.
“We’re really concerned,” Mr. York said. “This is the most ponds that have had algae advisories in Mashpee that I am aware of.”
Santuit Pond is the pond in Mashpee that is most notorious for cyanobacteria blooms. In July, the Mashpee Health Department posted a health advisory at Santuit Pond for the fourth consecutive year.
An advisory also remains in place at Mashpee/Wakeby Pond, where the health department posted an advisory after a scum layer of cyanobacteria was discovered in September.
Andrew R. Gottlieb, executive director of the Association to Preserve Cape Cod, said cyanobacteria is a growing problem not just in Mashpee and across Cape Cod, but worldwide.
“It’s a big emerging problem,” said Mr. Gottlieb, who is also a Mashpee selectman. “It’s not a Mashpee-only problem; it’s national and global.”
The APCC runs a cyanobacteria monitoring program that monitors cyanobacteria levels in freshwater ponds in nine towns on Cape Cod.
In the past five years, Mr. Gottlieb said, “we have found cyanobacteria to be more widely distributed across ponds than expected, at greater concentrations than expected and for longer portions of the year.”
Cyanobacteria occur naturally, but Mr. Gottlieb said human activity has led the blue-green algae to proliferate to dangerous levels.
“At their ecologically balanced level cyanobacteria are not a problem,” Mr. Gottlieb said. “It’s when we put a thumb on the scale and distort the water-quality conditions to the point we allow cyano[bacteria] to outcompete other aquatic lifeforms, plant lifeforms, we get into trouble.”
The two major factors contributing to the prevalence of cyanobacteria on Cape Cod are warming temperatures and an excess of nutrients in freshwater ponds, he said.
“To the extent that people are thinking that climate change doesn’t really affect them yet, well, yes, it does,” Mr. Gottlieb said.
Warming temperatures have provided cyanobacteria with more-ideal conditions in which to grow, he said. Meanwhile, an excess of phosphorus making its way into freshwater ponds from human sources acts as a fertilizer, further fueling the growth of cyanobacteria.
Septic systems, road runoff and fertilizers all contribute to the buildup of excess phosphorus in freshwater ponds, Mr. Gottlieb said.
“The best thing we can do is reduce nutrient inputs by changing how people use and apply fertilizers on lawns and gardens,” he said. “In the long term, this is a wastewater management issue, and it’s an issue that requires active involvement by the towns.”
Ashley Fisher, Mashpee’s director of natural resources, reiterated that climate change and human contributions to phosphorus levels in ponds fuel cyanobacteria growth.
“We’re only going to see this happen more with climate change,” Ms. Fisher said.
After what was a particularly hot summer, cyanobacteria levels at Santuit Pond surpassed 480,000 cells per milliliter in September, the highest level ever recorded by the natural resources department, Ms. Fisher said.
“It’s yard use. The lawn infatuation needs to end, we are in a drought; your yard should look like my yard. My yard is a nice shade of brown,” she said. “When you go to these areas that abut the ponds and lakes and you see a fluorescent green lawn, something isn’t right—they’re adding something.”
The director of natural resources called on residents to change their mindset when it comes to lawn care. Fertilizing lawns contributes to the amount of phosphorus entering the ponds, and on Cape Cod, “water is life,” she said.
The prevalence of cyanobacteria “will affect people’s property values, it will affect everything,” Ms. Fisher said. “It will affect tourism in the area, thus it will affect the economy here in Mashpee.”
Ms. Fisher noted that Cape Cod has a so-called “blue economy” that relies on water resources such as ponds, streams and bays.
“Everything on the Cape is reliant on our waterways,” she said.
Moreover, the issue of cyanobacteria is an issue of public health with potential health risks for humans or pets who make contact with or consume cyanobacteria-laden water, she said.
The Mashpee Natural Resources Department, with the help of volunteer water-quality monitors like Mr. York, continues to take weekly samples at Santuit Pond and Ashumet Pond, she said.