What does water pollution most directly cause in aquatic ecosystems?

• A. Greater genetic diversity among terrestrial plants
• B. Increased atmospheric carbon dioxide
• C. Enhanced soil fertility
• D. Decreased dissolved oxygen levels

Answer: (D)

Verified step by step guidance

1. Understand the concept of water pollution: Water pollution refers to the contamination of water bodies (like rivers, lakes, and oceans) with harmful substances such as chemicals, waste, or microorganisms. These pollutants can disrupt the balance of aquatic ecosystems.
2. Learn about dissolved oxygen: Dissolved oxygen (DO) is the amount of oxygen present in water, which is essential for the survival of aquatic organisms like fish, invertebrates, and microorganisms. Healthy ecosystems typically have sufficient levels of dissolved oxygen.
3. Connect water pollution to dissolved oxygen levels: Pollutants such as organic waste or chemicals can lead to increased microbial activity. Microorganisms decompose organic matter, consuming oxygen in the process, which reduces the dissolved oxygen levels in the water.
4. Understand the consequences of decreased dissolved oxygen: Low dissolved oxygen levels can lead to hypoxic conditions, where aquatic organisms struggle to survive. This can result in fish kills, loss of biodiversity, and disruption of the food chain in aquatic ecosystems.
5. Recognize why other options are incorrect: Greater genetic diversity among terrestrial plants, increased atmospheric carbon dioxide, and enhanced soil fertility are not direct consequences of water pollution in aquatic ecosystems. The most direct impact is decreased dissolved oxygen levels.