Does duckweed or other floating plants aerate water?

Question

I know that if these floating plants cover a body of water, it depletes oxygen but does it itself aerate the water in any amount

Answer 1

Yes, algae/duckweed will release some oxygen into the water.  The oxygen depletion from an algal bloom results mainly from the bacteria that eat dead algae.  Algae have a fast turnover rate (they die and regrow very fast), so there is always plenty of dead algae for bacteria to feed on.  In turn, the bacteria use up all the oxygen.