AQA BIOL4 6.5 - Environmental consequences of using nitrogen fertilisers

Reduced species diversity
- The fertilisers favour the growth of rapidly growing species (grass) and so they out-compete many other species which die as a result

Leaching
- Pollution of watercourses (flowing body of water)

Eutrophication
- Caused by leaching of fertiliser into watercourses

Nitrate is normally a limiting factor in rivers, however when nitrates leach into the river it is no longer a limiting factor and plants and algae grow exponentially. Algae grow at the surface, so there is a dense algal bloom which absorbs light so plants can no longer survive. This enables saprobiotic algae to grow exponentially as there are plenty of dead plants. As the saprobiotic bacteria require oxygen for respiration, the concentration lowers in the river and becomes a limiting factor for aerobic organisms (like fish). As there are less aerobic organisms, anaerobic organisms can grow exponentially. These anaerobic organisms release more nitrates and toxic wastes (such as hydrogen sulphide) which make the water well putrid! :)

The process by which salts build up in bodies of water