Question

why is eutrophication harmful to ecosystems?
a eutrophication causes deforestation.
b eutrophication depletes dissolved oxygen in water.
c eutrophication can cause acid rain.
d eutrophication changes the amount of greenhouse gasses in the atmosphere.

Explanation:

Eutrophication occurs when water bodies receive excess nutrients, leading to excessive growth of algae. When these algae die and decompose, bacteria consume oxygen in the water during the decomposition process. This depletion of dissolved oxygen in water (hypoxia) is harmful as it can suffocate fish and other aquatic organisms.

• Option A: Deforestation is mainly caused by human activities like logging, urbanization, etc., not eutrophication.
• Option C: Acid rain is caused by emissions of sulfur dioxide and nitrogen oxides which react with water in the atmosphere. Eutrophication is not a cause of acid rain.
• Option D: Greenhouse gas (like carbon - dioxide, methane) levels in the atmosphere are affected by activities like burning of fossil fuels, deforestation, etc. Eutrophication does not directly change the amount of greenhouse gases in the atmosphere.

Answer:

B. Eutrophication depletes dissolved oxygen in water.