Question

In a lake near a farm the growth of algae suddenly increased. This increase was most likely due to which of the following?
A. a decrease in air temperature B. a decrease in water level
C. fertilizer runoff from the farm D. exhaust gases from farm equipment

Answer 1

a decrease in air temperature

Answer 2

It's actually option C) fertilizer runoff from the farm.

The excess fertilizer used in a farm gets washed away by the water drainage to the nearest waterbodies like lake. There algal growth rises due to the elevated conditions for their proper growth. This causes shortage of oxygen in the waterbody further causing death of other organisms present in it. This is one of the harmful effect of the excess use of fertilizers in farm.