Long known for its crystal-clear water, Lake George in New York experienced its first confirmed harmful algal bloom in 2020, turning the lake pea-soup green. Runoff, especially from extreme rainfall events, dumps pollutants such as road salt into the lake, says Eric Siy, president of the nonprofit Lake George Association. Road salt can lurk in soil and streams and on roadsides until it washes into lakes. And it doesn’t just provoke algal blooms. Earlier this year, an international study in PNAS revealed that aquatic food webs are much more sensitive to salt than previously known. Researchers looked at the impact of salt on plankton living in lake water samples from 16 sites in North America and Europe. They found it takes less than a teaspoon of salt in five gallons (19 liters) of water to harm aquatic life — a concentration lower than recommended limits in every nation in the study. Rick Relyea, senior endowed chair at Rensselaer Polytechnic Institute’s Darrin Fresh Water Institute and one of the study’s authors, says governments had very little information to go on when they set the current limits. “With the new data, there’s an opportunity to revisit those thresholds. There’s an opportunity that wasn’t there five years ago, in terms of integrating more data, orders of magnitude more data,” he says. Balancing Act New thresholds could be crucial because salt can throw entire ecosystems out of balance. It damages aquatic biodiversity, affecting plankton, fish, amphibians and plants. Salt doesn’t have to kill off a species to change a lake’s ecology. “At some point, things are just going to start dying. By the time you get there, that’s pretty extreme,” says Flora Krivak-Tetley, co-author of several studies on the growing menace of road salt to aquatic ecosystems. “Zooplankton are the canary in the coal mine because they are the most sensitive organisms in the water. If you protect zooplankton, you often protect other animals.” —Rick Relyea For example, a decline in one species can lead to an increase in another. This happens with tiny aquatic animals called zooplankton that graze on microscopic plants called … Continue reading Lakes are more sensitive to salt than we thought