Which statement best describes the relationship between BOD and eutrophication?

Which statement best describes the relationship between BOD and eutrophication?

• A. Low nutrient input
• B. Higher water clarity
• C. Significant organic pollution and eutrophication
• D. No oxygen use by microbes

Answer: (C)

BOD measures how much oxygen microbes need to decompose organic material in water. In eutrophic systems, excess nutrients drive algal blooms; when these organisms die, their organic matter is broken down by microbes, which increases oxygen demand. This rise in BOD and the resulting decrease in dissolved oxygen reflect significant organic pollution linked to eutrophication, so that statement is the best description. The other ideas don’t fit: low nutrient input would reduce eutrophication, clearer water is typical of low nutrients, and microbes do use oxygen rather than avoiding it, which is why high BOD signals oxygen depletion.

BOD measures how much oxygen microbes need to decompose organic material in water. In eutrophic systems, excess nutrients drive algal blooms; when these organisms die, their organic matter is broken down by microbes, which increases oxygen demand. This rise in BOD and the resulting decrease in dissolved oxygen reflect significant organic pollution linked to eutrophication, so that statement is the best description. The other ideas don’t fit: low nutrient input would reduce eutrophication, clearer water is typical of low nutrients, and microbes do use oxygen rather than avoiding it, which is why high BOD signals oxygen depletion.