A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this
(a) Lots of urea and phosphate fertilizer were used in the crops in the vicinity
(b) The area was sprayed with DDT by an aircraft
© The lake water turned green and stinky
(d) Phytoplankton populations in the lake declined initially thereby greatly reducing
photosynthesis
Which two of the above were the main causes of fish mortality in the lake?
(1) a, b
(2) b, c
(3) c, d
(4) a, c
Sol. Answer (4)
Lots of urea and phosphate fertilizers used in crops in the vicinity of lake will lead to
eutrophication that means the lake will turn green and stinky.