One indicator of aquatic health is BOD levels, which measures biological oxygen demand. Healthy systems have low BOD levels. A high BOD level indicates .

Question

a
A highly polluted system due to abundant silt particles
A highly pure water system
b with an abundance of
autotrophs
A highly polluted system due to an excess of nutrients
d None of the above

Answer 1

A high BOD (Biological Oxygen Demand) level indicates a highly polluted system due to an excess of nutrients. This is because high BOD values suggest that there is a significant amount of organic matter present, which microbes break down, consuming oxygen in the process. This increased microbial activity often results from nutrient pollution, such as from fertilizers or sewage, leading to lower dissolved oxygen levels in the water and poor aquatic health.

So the correct answer is: A highly polluted system due to an excess of nutrients.