If you’re around a lake, pond, or the still reaches of a stream around the Long Island Sound region, see if you can find a freshwater snail suctioned to a plant or gliding along the mud.
If you pick one up, the snail will likely slurp its soft head and muscular foot back into its brittle, coiled dome. Inside that protective house, the snail has a heart, kidney, stomach, and other internal organs. Here’s an interesting quirk of snail anatomy you can share with friends at the next hangout—some aquatic snails have a lung, others have gills, and some have both.
Freshwater gilled snails rely on dissolved oxygen in the water. When a lake or stream has excess nutrients from fertilizer runoff or sewage overflow, algae may bloom and cause a decrease in oxygen levels, which harms gilled species. A water body with a plethora of lunged snails and a miniscule number of gilled snails may be indicative of elevated levels of pollution.
While the cerebral ganglia, or snail “brain,” may be unaware of its pollution-testing tendencies, we celebrate their existence and ecosystem roles as grazers of algae, food sources for other animals, and decomposers of dead organic matter. We are working hard to monitor and prevent pollution so snails—along with many other wildlife species and our own human communities—can enjoy clean water.
Save the Sound conducts testing in our lab for the fecal-indicating bacteria Enterococci, E. coli, and Fecal Coliforms as well as water quality parameters including dissolved oxygen, turbidity, chlorophyll-a, salinity, and temperature.
In fact, during the summer seasons, you can get involved in water quality monitoring with us. We recruit volunteers in late spring and early summer every year for our 12-week Bactria Monitoring Program in areas including Queens, Westchester County, and Greenwich. Check out the results from past seasons here. If you’re reading this in June or July this year (2025), we’re especially looking for volunteers to collect samples in Mamaroneck on Wednesdays between 10:00 a.m. and 1:00 p.m. To help us collect samples in the summer, please fill out, scan, and return the volunteer form.
Written by Betsy Painter, Science Writer and Communications Consultant for Save the Sound.