No, the water in the Great Lakes is freshwater.
The Great Lakes, a chain of large freshwater lakes in eastern North America, are classified as freshwater ecosystems. Unlike oceans which are characterized by high salinity, the Great Lakes contain very low concentrations of salt.
Understanding Freshwater vs. Saltwater
The key difference lies in the amount of dissolved salts, primarily sodium chloride. Saltwater bodies, like oceans, have an average salinity of around 35 parts per thousand (ppt), which is roughly 35 grams of salt per liter of water. Freshwater bodies, on the other Lakes, have very low salt concentrations, typically less than 1 ppt.
Salt Levels in the Great Lakes
Based on available information, the Great Lakes are definitively freshwater. For example, Lake Michigan is traditionally known for having very low salt levels. Historically, levels of substances like chloride were around one milligram per liter of water. While our activities have led to increases over time—Lake Michigan's chloride levels have gradually climbed to around 15 milligrams per liter—these levels are still extremely low compared to saltwater environments and well within the range considered freshwater.
Impact of Increasing Salinity
While the Great Lakes remain freshwater, the gradual increase in salt levels, often due to factors like road salt runoff, is a concern for the ecosystem's health. These changes, although minor in the context of saltwater, can affect:
- Aquatic life sensitive to salinity changes.
- Water quality for drinking and other uses.
In summary, the vast volume of water in the Great Lakes is freshwater, supporting a unique array of plant and animal life adapted to low-salinity conditions.
