Question

What is 'eutrophication'? Write its two harmful effects.

Answer 1

Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both. Eutrophication can be a natural process in lakes, occurring as they age through geological time.

Eutrophication can have serious, long-term effects. The most notable effect of eutrophication is algal blooms. 
The main effects caused by eutrophication
1. Species diversity decreases and the dominant biota changes
 2. Plant and animal biomass increase
3. Turbidity increases

Answer 2

and it's two harmful effects are---
1-species diversity decreases and the dominant biota changes.
2-plant and animal biomass increases.