Why is freshwater biodiversity important and how can pollution impact it?

• A. Biodiversity is not essential to ecosystem services.
• B. Freshwater biodiversity sustains ecosystem services; pollutants can alter habitats, reduce species richness, disrupt food webs, diminish ecosystem function.
• C. Pollution only affects taste of water.
• D. Pollution always increases species richness.

Answer: (B)

Freshwater biodiversity supports the services that ecosystems provide, such as clean water, nutrient cycling, habitat for organisms, and resilience to disturbances. Pollution can change the living conditions in rivers, lakes, and streams by altering chemistry and habitat quality, introducing toxins, and increasing sediments or algal blooms. These changes often reduce the number of species (lower species richness) and disrupt how organisms interact in food webs, which weakens the whole system’s ability to function properly. When biodiversity declines and food webs are disrupted, ecosystem processes like decomposition and water purification become less stable, so the services we rely on decline. That’s why this option is the best: it captures how biodiversity underpins ecosystem services and how pollutants can harm habitats, reduce richness, disrupt interactions, and diminish ecosystem function. The other statements miss or contradict these points, such as claiming biodiversity isn’t essential, that pollution only affects taste, or that pollution always raises species richness.