Eutrophication Links Fertilizers to Oxygen Depletion

Steps:

• Statement 1 is correct: Low dissolved oxygen (hypoxia) prevents fish survival in lakes.
• Statement 2 is correct: Runoff fertilizers add nutrients like nitrates/phosphates, triggering eutrophication.
• Eutrophication causes algal blooms that die and decompose, consuming oxygen via bacterial respiration.
• Thus, statement 2 explains statement 1 through this oxygen-depleting process.

Why A is correct:

• Eutrophication definition: Nutrient enrichment leads to excessive algae growth and subsequent oxygen depletion during decomposition, directly causing insufficient oxygen for fish.

Why the others are wrong:

• B: Incorrect because eutrophication from fertilizers does explain oxygen shortages.
• C: Incorrect because statement 2 accurately describes fertilizer-induced eutrophication.
• D: Incorrect because statement 1 correctly identifies oxygen as a limiting factor for fish.

Final answer: A