Road salt harms freshwater snails ^{CEFR B1}

Freshwater streams, ponds and lakes across the United States are becoming saltier because road salt from winter deicing enters fresh water through road runoff. Rick Relyea and colleagues at the University of Missouri ran semi-outdoor experiments that combined different salt levels with the presence or absence of predator species to reflect real conditions. Relyea notes that freshwater organisms evolved in low-salt environments.

The team found that road salt became much more deadly when snails also experienced the fear of predators. At the highest salt levels, predator stress dramatically increased snail deaths, causing nearly 60% higher mortality compared to salt alone. Researchers observed that snails slowed their eating and moved less to avoid detection, while higher salt forced snails to use more energy to survive. Together, these changes appeared to drain snails and raise their risk of death. Scott Goeppner says such effects do not show up in typical lab studies and so scientists may underestimate the danger of common pollutants like road salt.

Although small, freshwater snails are abundant and important: they help control algae, recycle nutrients and provide food for fish and birds. Goeppner warns that if snails disappear, algae can grow unchecked and lower water quality, affecting the waterways communities rely on every day. Relyea says practical steps can reduce salt pollution. Communities can cut road salt use by up to 50% while still maintaining safe roads. Simple measures include pretreating roads, calibrating salt trucks and applying salt more strategically. The study appears in the journal OIKOS. Mitchell Le Sage at Rensselaer Polytechnic Institute is a coauthor. Source: University of Missouri.