It can produce liver and nerve toxins, asthma-like symptoms, severe vomiting and diarrhea; it frequently kills pets; and in rare cases it triggers temporary blindness and even death for humans.
The potentially deadly villain is called "toxic blue-green algae" and can occasionally be found in your favorite lake or pond, as it was last year in Bolton Lake. A new report warns dangerous freshwater "blooms" may be happening more frequently due to global warming.
Yet there is no national system for monitoring these outbreaks. Environmental officials in Connecticut say they really don't know how common toxic algae is in this state because (until just recently) they weren't keeping track.
"We haven't been keeping records or doing monitoring," says Chuck Lee, an environmental analyst with the state's lake management unit for nearly 30 years. He says Connecticut only began checking on toxic algae blooms this past summer, and was the last state in New England to start up a monitoring program.
"I think we need to do more monitoring," Lee says. "I wouldn't want to say [toxic algae outbreaks in Connecticut] are rare... We do have lakes with pretty intense algae blooms that we're concerned about."
This concern isn't something isolated to one body of water in Connecticut. State Department of Energy & Environmental Protection experts say they've been looking at big algae blooms in ponds and lakes that include Lake Lillinonah and Lake Zoar (in the Housatonic River Valley); Candlewood Lake; and Beseck Lake (in Middlefield).
Not all algae blooms are toxic. And those that are don't necessarily make it easy to tell.
A warning on the DEEP's web page explains that blue-green algae occurs naturally in Connecticut freshwater lakes and ponds and most often causes no problems.
The ones that do create toxins that include "microcystin," "anatoxin-a," "cylindrospermopsin," "saxitoxins," and "lipopolysaccharides."
The agency's warning (put up this past July) goes on to list those potentially nasty health effects from swimming in or drinking water from a toxic bloom. And these outbreaks can create an unholy stench for people living nearby.
The toxins can also accumulate in fish that swim through the algae, and get into the people who catch and eat those fish. "Dogs are especially at risk from exposure to blue-green algae blooms," DEEP officials added, because water-loving pups will drink the toxic stuff or lick it off after going splashing around.
"Assessing the potential health effects from blue-green algae blooms is complicated because...the bloom may not be producing toxins. Therefore, chemical analysis of the water is needed to verify if a blue-green algae bloom is releasing toxins," DEEP's web-page warning states.
And therein lies a big part of the problem.
A report titled "Toxic Algae: Coming Soon to a Lake Near You?" was released last month by the National Wildlife Federation and Resource Media.
In it, experts said it's tough to determine the extent or danger of toxic freshwater blooms because there's no federal agency assigned to track them; few studies have been done on the economic impact of these blue-green baddies; and lots of states have no formal monitoring program.
(The only federal freshwater monitoring program is happening in Lake Erie. The feds do fund toxic outbreak research and testing for marine and coastal areas.)
A list put out by the U.S. Environmental Protection Agency shows only 23 states currently have monitoring and testing programs for toxic algae.
This past summer (between May and mid-September), 20 states across the nation reported 147 toxic freshwater blooms.
New York topped the list with 50 toxic algae occurrences, but the report's experts noted that was probably because New York has one of the best monitoring systems in the nation. Massachusetts reported three outbreaks; New Hampshire, two; and Rhode Island, one.
Lee and Brian Toal, an epidemiologist with the Connecticut Public Health Department, say they saw no reports of toxic blooms in this state this summer. But again, state officials here have only just begun to create a monitoring program, and Connecticut leaves the responsibility for dealing with toxic blooms up to municipal and local health officials.
"We realize there are lakes and ponds that are blooming; we just haven't gotten called about it," says Toal.
The most recent documented toxic bloom in this state happened in Lower Bolton Lake in August 2012. The Eastern Highlands Health District, which covers that portion of northeastern Connecticut, issued a public warning advising people to avoid contact with the lake's water and prevent pets from drinking or playing in the lake.
Robert Miller, health director for the district, says the public advisory was in effect for 7-8 weeks, and wasn't taken down until after the Labor Day weekend. He says the toxic bloom "just naturally waned and expired on its own," which experts say isn't unusual.
As far as can be determined, the Lower Bolton Lake bloom didn't make any person or animal sick, according to Miller. He says it was the first time he knows about that local and state health officials attempted to cooperate to create a "structured response" to a toxic bloom in Connecticut.
It was that outbreak that prompted Connecticut state officials to put out a detailed 14-page "guideline" for local officials and citizens on how to recognize and deal with toxic algae blooms. Miller says he believes those are "interim guidelines" and that state officials are hoping to create a better monitoring and response system down the line when they have more data.
According to the National Wildlife Federation report, the most serious triggers for these toxic outbreaks is the fertilizer being flushed into streams, rivers, lakes and ponds from farms and suburban lawns. All those excess nutrients create a perfect diet for hungry toxic algae.
All this pollution is being made worse by climate change, according to the report's authors. "Global warming and intensification of major storms and droughts play major roles in the spread of toxic blue-green algae blooms worldwide," said Hans Paerl, a professor of marine and environmental sciences at the University of North Carolina.
"The interesting thing I kind of discovered," Miller says about his first exposure to these hazardous blooms, "is that there's a lot we don't know about toxic algae... about how it exists, and the implications for health and recreation."
Lee agrees. He says that's a major reason why the state has finally begun an initial program to start monitoring some of these inland bodies of water.
"We want to have a better understanding about where we need to be concerned," says Lee.