Posted: 24/05/2014 at 19:27
My brother who had a degree in horticulture told me about hydroponics in the early seventies. The highly nutritious liquid that the plants are grown in is then poured away; makes it's way into lakes and rivers, giving them a very high level of nutrients. This encourages the plants in the water to grow far larger than they normally would. This de-oxygenates the water and you then have dead lakes and rivers.
I hope I have not explained this badly, I am not a scientist, I simply remember what I was told by someone who was.