During eutrophication, what happens to dissolved oxygen (O2) levels as biochemical oxygen demand (BOD) increases?

During eutrophication, what happens to dissolved oxygen (O2) levels as biochemical oxygen demand (BOD) increases?

• A. O2 declines
• B. O2 rises
• C. O2 remains unchanged
• D. O2 fluctuates

Answer: (A)

During eutrophication, nutrients fuel algal blooms and more organic material in the water. Biochemical oxygen demand (BOD) is a measure of how much oxygen microorganisms need to decompose that organic matter. As BOD rises, these microbes consume more dissolved oxygen through respiration, so the available oxygen in the water drops. This leads to lower dissolved oxygen levels, which can stress or kill aquatic life. Keep in mind that daytime photosynthesis by algae can temporarily raise oxygen, but the overall effect of higher BOD is a decline in O2.

During eutrophication, nutrients fuel algal blooms and more organic material in the water. Biochemical oxygen demand (BOD) is a measure of how much oxygen microorganisms need to decompose that organic matter. As BOD rises, these microbes consume more dissolved oxygen through respiration, so the available oxygen in the water drops. This leads to lower dissolved oxygen levels, which can stress or kill aquatic life. Keep in mind that daytime photosynthesis by algae can temporarily raise oxygen, but the overall effect of higher BOD is a decline in O2.