dirty eutrophic water

aquatic biomass blanket blanketweed brown canal choking contamination covered dense deoxygenate deoxygenating depletion dirt dirty ditch duckweed environment eutrophic eutrophication floating foam green lake layer leaves lemna nature nutrients organic oxygen polluted pollution pond rotting scum slime stagnant stinking suffocate suffocating surface vegetation water waterweed weed weeds white