By PAULA TRACY, InDepthNH.org
CENTER HARBOR – An unprecedented outbreak of cyanobacteria blooms across Lake Winnipesaukee in mid-June has aquatic biologists looking at a few potential causes, including one that relates to a newly discovered invasive species.
Pat Tarpey, president of the Lake Winnipesaukee Association, said there were about 70 reports to the state Department of Environmental Services about these blue green algae blooms of scum identified in most all bays and even in the Broads of the state’s largest lake in June, but they have thankfully disappeared on the big lake.
The blooms, which can cause illness in humans from rashes to a form of dysentery, can kill pets and livestock. People are warned to stay away from the areas of water bodies that have alerts or advisories.
As of Friday, the state had two cyanobacteria alerts and two advisories.
The advisories are for Cobbetts Pond in Windham and Gorham Pond in Dunbarton.
The alerts are active for Lee’s Pond in Moultonborough and Long Pond in Pelham.
The state also has issued five fecal bacteria advisories for high levels of e coli at Pawtuckaway State Park Beach, FB Argue Recreation Area Beach in Pittsfield, Twin Mountain Recreation Beach, Pirate’s Cove and Day Use Beach at Bear Brook State Park.
A beach advisory is issued when a water sample contains fecal bacteria levels that exceed the state standard, indicating unhealthy swimming conditions.
Possible sources of fecal contamination include wastewater treatment plants, failing septic systems, domestic and wild animal waste, and stormwater runoff, according to the DES website.
For more information, visit https://www.des.nh.gov/water/healthy-swimming/harmful-algal-blooms
For InDepthNH.org reporting on NH lake health: https://indepthnh.org/series/lake-health-nh/
David Neils, chief aquatic biologist and director of The Jody Connor Limnology Center within the Watershed Management Bureau of the Department of Environmental Services, said Friday that scientists are developing more data about the rash of cyanobacteria blooms on Winnipesaukee earlier this summer and trying to understand what happened on a lake that is 44,000 acres in size.
“We are working on some hypotheses,” about what changed in the lake, but he said a lot of it has to do with an especially rainy summer in 2023, a lack of ice in the past winter, the amount of shoreland development and a weaker theory but possible contributor, the introduction of the invasive Spiny Water Flea found for the first time in Lake Winnipesaukee last fall.
“Other locations have identified (spiny water flea) as changing the food web,” Neils said and may allow for more cyanobacteria growth.
On June 21, there were cyanobacteria warnings listed for areas of Lake Winnipesaukee in Wolfeboro, Tuftonboro, Moultonborough, Center Harbor, Meredith and the Broads in Gilford with the only part of the lake not reporting blooms in Alton.
While there have been occasional reports of cyanobacteria in one bay or another on Winnipesaukee, Tarpey said this was the first time for such a widespread outbreak on the big lake.
And it got peoples’ attention.
However, she noted that scientists did not believe it is due to a problem in the past on Lake Kanasatka which flows into Winnipesaukee in Moultonborough.
Neils said there is not a lot of monitoring of tributaries to the lake but there is a significant amount of monitoring of the lake itself.
The problem of cyanobacteria is due to excess nutrients delivered by stormwater into the lake.
The large body of water, he said, only flushes out every five years but “it had to do with a rainy year prior,” he said.
Add to that the fact that the winter was relatively warm with ice not forming in some of the deepest and most open areas of the lake until February and ice out declared in early April, clearly two weeks earlier than average, Neils said.
The cold water in winter and ice act as a sort of reset button, scientists said, killing out some of it and making it slow to grow in spring.
Temperatures in the lake were three degrees warmer than a typical spring, Neils said, noting it was studied over 50 days with the lake getting to 60 degrees 10 days earlier than usual.
“Cyanobacteria typically thrive in warm water,” he said.
He also noted there is significant development along the shoreline of the lake which continues each year and impacts the water.
Finally, he said, scientists are looking closer at this new invasive species in the lake, the spiny water flea, which was likely introduced into the water body by a boat with water from an infested water body.
Biologists from the New Hampshire Department of Environmental Services documented the presence of fleas, its proper name “Bythotrephes longimanus” on Sept. 13, 2023, in the Winnipesaukee Broads. Subsequent testing found it in the Alton and Wolfeboro areas of the lake.
The spiny water flea is a microscopic animal, also known as zooplankton, that is native to Europe and Asia.
According to DES data, spiny water fleas were first introduced to the United States to the Great Lakes in the 1980s.
The nearest locations of other spiny water flea infestations include Lake Champlain in Vermont, and Lake George and a few other water bodies in New York.
The tiny flea was likely introduced by transient boaters who visited a waterbody with an existing infestation. Live organisms or eggs were probably transported to Lake Winnipesaukee on recreational or fishing gear or in the live well or bilge of a boat.
There are no treatments available to control this species once it is established, therefore the best, and only management option, is preventing introduction into uninfected water bodies by cleaning, draining and drying all vessels and recreational gear after leaving a waterbody as required by state law.
The spiny water flea is not harmful to humans, however, it can be a nuisance when it builds up on fishing lines. It can also negatively impact aquatic food webs by changing the plankton community which can, in turn, influence fish populations.
In a press release announcing the discovery last year, John Magee, Programs Supervisor with the Inland Fisheries Division at the New Hampshire Fish and Game Department, said, “Some of our native fish species could be impacted by this…At high densities, the spiny water flea can outcompete native zooplankton on which some of our native fish species rely.”
Neils said NHDES biologists have been monitoring this species for the past eight years, anticipating eventual detection in New Hampshire but this was the first time it was seen here.
“Invasive species are very good at spreading to new locations,” said Kirsten Hugger, an Aquatic Ecologist with NHDES. “We anticipated there was potential for introduction to Lake Winnipesaukee due to boater traffic, which is why we initiated a monitoring program in 2016. However, it is still surprising and disappointing to have confirmed that spiny water fleas are in New Hampshire.”
The link with cyanobacteria is still being analyzed, but Neils said it is possible that this predator plankton is eating that which consumes cyanobacteria.
Cyanobacteria (formerly known as blue-green algae) are photosynthetic bacteria that use the sun’s energy but also behave as bacteria.
According to the DES, cyanobacteria are some of the earliest inhabitants of our waters. They naturally occur in most of our lakes, though often in relatively low numbers in New Hampshire.
Many species of cyanobacteria grow in colonies to form surface water “blooms.” Blooms are diverse in appearance. They can range in color from green, blue-green, yellow, white or black and consist of thousands of individual cells.
Although most often seen when floating near the surface during the swim season, many cyanobacteria spend most of their life cycle suspended throughout the water column, regulating their buoyancy to suit their needs.
Cyanobacteria can also overwinter, surviving on the lake bottom during the winter months. Increased water temperature and light in the spring promote the upward movement of cyanobacteria through the water column toward the surface where blooms or scums are often formed.
According to the World Health Organization, toxic cyanobacteria are found worldwide in both inland and coastal waters. The WHO has documented acute impacts to humans from cyanobacteria from the US and around the world as far back as 1890.
While most human health impacts have resulted from ingestion or injection, cases of illnesses have also been attributed to swimming in cyanobacteria infested waters.
The Center for Freshwater Biology at the University of New Hampshire is currently examining the potential impacts of these toxins upon the lake food web and from aerosols.
Exposure to toxic cyanobacteria scums may cause various symptoms, including nausea, vomiting, diarrhea, mild fever, skin rashes, eye and nose irritations, numbness and general malaise. Some studies suggest cyanobacteria may be linked to serious illness.
The first reports of toxic cyanobacteria in New Hampshire occurred in the 1960s and 1970s but have been growing in recent years and 2024 started out as the worst.
For more information, visit https://www.des.nh.gov/water/healthy-swimming/harmful-algal-blooms
