Final answer:
Dams can disrupt salmon migration by obstructing their natural spawning routes, affecting the ecosystems by altering water conditions and potentially leading to declines in salmon populations.
Step-by-step explanation:
The question asks about the consequences of dams protecting habitats for salmon populations in the Great Lakes, which have toxic chemicals. The presence of dams can disrupt salmon migration, as these structures can obstruct the fish's natural routes used for spawning. Moreover, dams can affect the surrounding ecosystems in various ways, such as changing water temperatures, chemistry, flow characteristics, and sediment loads. These changes can lead to significant alterations in the ecology and physical characteristics of the river both upstream and downstream from the dam. Specifically, salmon are known for their migratory patterns to spawn, and dams present a significant barrier to these movements, resulting in potential declines in their population.