Question

Excessive accumulation of organic matter in water leads to

• A. Decrease in species diversity
• B. Increase in species diversity
• C. Greenhouse effect
• D. No effect of species diversity

Answer 1

The correct option is A Decrease in species diversity

Eutrophication is a condition in an aquatic ecosystem where high nutrient concentrations stimulate blooms of algae (e.g., phytoplankton). Biological oxygen demand becomes high and therefore, the dissolved oxygen (DO) is reduced. Due to the low DO, many species of plants and animals die leading to a decrease in species diversity. In most cases, if dissolved oxygen concentrations drop below 5 parts per million (ppm), fish would be unable to live for very long. All clean water species such as trout or salmon would die even well above this level of dissolved oxygen, and low oxygen fish such as catfish and carp will be at risk below 5 ppm.