Question

nail what are the patches of green layer floating on the surface of stagnant water bodies like bones and lake consists of

Answer 1

HEY DEAR....
YOUR ANSWER⬇
Those floating things are nothing but fungi and algal growth. These include Spirogyra and tannins (phytoplankton) mainly which makes the water appear green, brown or even red in colour.
I HOPE YOU FIND IT HELPFUL.
YOUR FRIEND.
#LAKSHMI... :-)