Scientists lowered Ontario lake pH for 17 years; trout still haven't recovered
A groundbreaking 17-year study on Lake 223 in Ontario revealed a complex response to acid rain. While the water chemistry has recovered since the experiment ended, the ecosystem is lagging behind. Fish numbers have not rebounded as hoped, with growth rates remaining low. This underscores the vital message that true ecological healing involves much more than merely restoring chemical balance.
A landmark experiment on the effects of acid rain took place in Lake 223, a lake located in northwestern Ontario. From 1976 to 1993, researchers deliberately introduced sulfuric acid to the lake over the course of 17 years to mimic the conditions of acid rain that were harming lakes in North America and Europe. During this time, the lake's pH decreased from 6.8 to 5.2, the lowest levels ever recorded for a lake in Ontario.
While the chemistry of the lake eventually returned to pre-experiment levels, the ecosystem has yet to fully recover. Lake trout populations are now at less than half of their pre-experiment numbers, and they are also growing more slowly. This slow recovery is believed to be linked to changes in the food web, including the disappearance of Mysis diluviana, a small freshwater shrimp-like invertebrate that played a crucial role in the lake's ecosystem.
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