blue-green algae cover the surface of the river with a pellicle. pollution of the river water. ecological problems

abstract algae algal background bad biodiversity bloom blooming bluegreen contaminated danger deficiency dirty ecology ecosystem environment environmental flora global green harmful hazard industrial industry landscape marsh microorganism natural nobody outdoor oxygen pattern pellicle phosphates phytoplankton plankton plant polluted pollution problem river scarcity slime summer surface swamp texture water