Nutrients alone aren't bad. They help some plants and animals grow. But since coral reefs live and thrive only in very clean, low-nutrient water, additional nutrients upset the balance of their environment. In the short run, nutrification may destroy coral and foraminifera, but it doesn't destroy the environment, per se. It changes it.
Nutrients feed plankton, stimulating their growth.
More plankton means more food for other animals, including predators and competitors for coral's space. As nutrification continues, the fatal end result is an oxygen-depleted environment in which only bacteria can live. And humans are doubling the amount of nutrients in the world, most of which end up in aquatic environments. Start pointing fingers, and it begins to get controversial. Small amounts of nutrients come from lots of places, Muller says, including septic systems, boat bilges, sewage outfalls, storm runoff and rainfall polluted by automobile exhaust.