Rich growth of micro-organisms consumes most of the dissolved oxygen, so as to deprive other organisms. It generally occurs at the bottom layers of deep lakes. Addition of excessive plant nutrients intensifies eutrophication. It is harmful to fish and other aquatic life.
A lake rich in organic waste will reduce the dissolved oxygen. The organic waste will increase biological oxygen demand of the lake thus depleting the O2 content and may result in dealth of fish.
increased population of aquatic organisms due to minerals
drying of the lake due to algal bloom
increased population of fish due to lots of nutrients