Once established, it is impossible to control the spread of the spiny water flea, an aquatic invasive zooplankton native to Eurasia that can alter the food webs of freshwater lakes.
In 2012, the invasive was found in Lake George, having already been detected in Great Sacandaga Lake, the Champlain Canal and the Glens Falls Feeder Canal.
In July of that year, a fisherman who was trolling the waters off Mallory Island presented a volunteer inspecting boats at DEC’s Mossy Point Launch with a cluster of small organisms attached to his fishing line.
The Lake George Association retrieved the sample and passed it along to RPI’s Darrin Fresh Water Institute (DFWI) in Bolton Landing, which confirmed its identity.
Jeremy Farrell, a Ph.d candidate in biology at the time, was among those who helped identify the tiny organism as the invasive flea.
Now a Senior Lecturer in Biology at RPI, Farrell and his colleagues at DFWI have been retained by the Lake George Park Commission to synthesize and summarize current and past research, including research about invasive species.
At a June 25 meeting of the Park Commission, Farrell happened to mention that between 2012 and 2016, the spiny water flea was responsible for the eradication of an entire population of an organism – a tiny, algae-eating crustacean called Daphnia pulicaria, whose presence in Lake George had been documented since the 1920s.
Farrell said he last sampled the lake for the presence of the organism in 2017, and at that time, none were found.
But then, suddenly, in 2016, “the spiny waterflea population collapsed,” Farrell told the Commissioners.
One of his students, who hoped to study the impacts of the spiny water flea on the lake’s zooplankton, had to transfer his research to other lakes.
No examples of spiny water flea were found in Lake George in 2017 and 2018. Two were found in 2019 and another two or three found in 2020.
“It was not detected again until 2021 and then the population rebounded,” said Farrell. “It was very large in the fall of 2023 – the largest we’ve ever seen.”
According to Farrell, an alteration in the food web, in the population of predators and prey, “likely has a large role in the crash of the spiny water flea population.”
But, he said, “we don’t really have a good hypothesis on what caused its return.”
Farrell said the absence and then reappearance of an invasive aquatic species is not entirely unfamiliar phenomenon.
Such populations are known as “sleeper populations,” he said.
Farrell referred us to a 2021 article in BioScience, a peer-reviewed journal, which noted, “The trigger that causes a sleeper population to irrupt does not need to be a sudden disturbance or perturbation. A gradual change in a driver such as climate can lead to an abrupt shift in the abundance of a population.” What triggered the irruption of Lake George’s spiny water flea population in the first place, what caused its demise and then its return in unprecedented abundance, is a topic for further research, said Farrell.
