Answer:
Choice D., elevated phosphorous and nitrogen in the water
Explanation:
The dead zone is caused by the enrichment of nutrients from the river, especially nitrogen and phosphorus. Most of the nitrogen supply comes from the main agricultural states. Â
Nitrates and phosphorus used in fertilizers have a key effect once they reach the river. They stimulate an explosive growth of algae, which when they die fall to the bottom of the sea and decompose. Â
The bacteria that break down the algae consume oxygen, in a process that drastically reduces the level of gas available for marine life.
