The type of bacteria that killed a Jack Russell terrier last year in East Hampton after the animal drank contaminated water has been found in two locations in Southampton.
Mill Pond and Lake Agawam are the first confirmed locations this year on Long Island to test positive for blue-green algae, which can be toxic to humans, pets and wildlife.
Twenty-four other freshwater ponds, lakes and streams statewide have been listed as either suspected of containing the bacteria or confirmed to be contaminated, according to the state Department of Environmental Conservation.
"All algae blooms should be avoided, but particularly blue-green algae blooms because they represent a risk," said Scott Kishbaugh, chief of the lakes monitoring and assessment section in DEC's water division.
Last year, a blue-green algae bloom was found in Georgica Pond and a dog that died after drinking water there tested positive for cyanobacteria. It was the only Long Island site where the algae was documented.
DEC, in conjunction with the state Department of Health, began monitoring water bodies for the algae in 2009. A confirmed case means there is enough of the bacteria to "create a recreational problem, a water quality problem or a health problem," Kishbaugh said.
The bacteria are naturally present but can pose a health risk in high levels. Drinking highly contaminated water has been associated with liver and nervous system damage. Mild exposure can cause skin, eye, nose and throat irritation, as well as inflammation of the respiratory tract, according to Department of Health fact sheet.
Blue-green algae can appear in many ways, such as green globs or dots on the water's surface. It can look like spilled blue, green or white paint, or pea soup, according to the DEC.
"The water just has this very green tint to it," said Chris Gobler, a professor at Stony Brook University's School of Marine and Atmospheric Science.
The algae also blocks out the sun, making it difficult to see the bottom of a water body, he said.
Blue-green algae blooms often occur in water bodies with high levels of nutrients, such as phosphorus and nitrogen. Low water or flow, and warm temperatures are contributing factors.
Mill Pond and Lake Agawam, which do not have swimming beaches, have had similar blooms in the past, and this year the outbreaks are large. "It's pretty much throughout both systems," Gobler said.
In late April, the Southampton board of trustees initiated an experimental treatment in Mill Pond to reduce phosphorus, which was blamed for a 2008 fish kill there.
The project, which the DEC permitted, involves using a mineral called Phoslock from Australia that absorbs phosphorus, trustee Fred Havemeyer said.
After several days of rain dumped on the region earlier this month, the bloom appeared, but has lessened, which Havemeyer attributed to Phoslock. "At this point, it looks like the blue-green algae has been beaten back to the very low levels that it was after the treatment," he said.
A second treatment is slated for next spring and results will be tracked. "We're in the process of reviewing that monitoring data," Kishbaugh said.