Ecologists from Spain are noticing chemical imbalances, changes in aquatic populations, and poor nutrient cycling in the river that runs through their country. Which of the following is the MOST likely cause of these issues?

A. runoff from high rainfall
B. a dam that was been built upstream
C. pesticides that have entered oceans
D. an oil spill in a local river

2 answers

B. a dam that has been built upstream

Building a dam can disrupt the natural flow of water, change sediment movement, and affect the habitat of aquatic species downstream. These disruptions can lead to chemical imbalances, changes in populations, and poor nutrient cycling in the affected river ecosystem.
Hugo is learning about how much of the world’s population lacks fresh water to run toilets in their homes. Which use of fresh water is Hugo concerned about?

A. manufacturing
B. food production
C. power generation
D. sanitation