Question

Which of the following is an example of an ecological effect of the removal of a large dam from the Elwha River in Washington State?

A. Seagrass beds near the river were lost due to increases in populations of salmon.
B. Conditions of the nearshore environment (that connects the river to the ocean) improved drastically.
C. Salmon disappeared from the river due to changes in water visibility.
D. The river became eutrophic due to increases in nutrient runoff.
E. Species diversity in the river decreased by 40%.

Answer 1

The ecological effect of removing a large dam from the Elwha River includes the drastic improvement of the nearshore environment (option B), which benefits from restored water levels, increased fish diversity and the return of salmon.

Step-by-step explanation:

The removal of a large dam from the Elwha River in Washington State is expected to have several ecological benefits. One primary ecological effect is improved conditions of the nearshore environment, which connects the river to the ocean. This is because the dam's removal restores naturally fluctuating water levels, which in turn can lead to increased fish diversity and better water quality. Specifically, in the Pacific Northwest, such projects are known to increase populations of salmon, a keystone species that plays a significant role in transporting nutrients to inland ecosystems.

Therefore, the correct answer to the student's question is B: Conditions of the nearshore environment (that connects the river to the ocean) improved drastically after the dam removal.