According to the Vermont Agency of Natural Resources, acid shock is caused when snow melts and acids that have been gathering in the snow are released into a body of water. The sudden change in water chemistry is known as acid shock.
Sulfuric and nitric acids get into the atmosphere from factory and vehicle emissions. After they combine with rain, snow and fog, the precipitation becomes acidic. When the acids trapped in snow enter water, they affect the new aquatic plant and animal life that develop during the spring. For example, if a water source becomes too acidic, sometimes frog eggs do not hatch. Acids also interfere with other chemicals in water, such as calcium. Crustaceans and mollusks need the nutrient to develop shells, but in acidic water, it is often unavailable.