Which of the following best describes how water pollution affects marine ecosystems?

• A. It prevents the formation of coral reefs by increasing water temperature directly.
• B. It causes rapid evolution in all marine species, increasing biodiversity.
• C. It can lead to decreased oxygen levels, harming aquatic organisms and disrupting food webs.
• D. It increases the salinity of ocean water, making it easier for all marine species to survive.

Answer: (C)

Verified step by step guidance

1. Understand the problem: The question asks how water pollution affects marine ecosystems. We need to evaluate the provided options and determine which one aligns with the known effects of water pollution on marine environments.
2. Step 1: Recall the concept of water pollution. Water pollution refers to the contamination of water bodies (like oceans, rivers, and lakes) by harmful substances such as chemicals, plastics, and waste. This can have various negative effects on aquatic ecosystems.
3. Step 2: Analyze the first option: 'It prevents the formation of coral reefs by increasing water temperature directly.' While water pollution can indirectly affect coral reefs (e.g., through sedimentation or chemical runoff), it does not directly increase water temperature. This option is not accurate.
4. Step 3: Analyze the second option: 'It causes rapid evolution in all marine species, increasing biodiversity.' Rapid evolution is not a typical or widespread result of water pollution. In fact, pollution often reduces biodiversity by harming sensitive species. This option is incorrect.
5. Step 4: Analyze the third option: 'It can lead to decreased oxygen levels, harming aquatic organisms and disrupting food webs.' This is accurate. Water pollution, such as nutrient runoff, can cause eutrophication, leading to algal blooms. When these algae die and decompose, oxygen levels in the water decrease, harming aquatic life and disrupting food webs.
6. Step 5: Analyze the fourth option: 'It increases the salinity of ocean water, making it easier for all marine species to survive.' Water pollution does not typically increase salinity, and increased salinity would not make it easier for all marine species to survive. This option is incorrect. Therefore, the correct answer is the third option.