Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course


4.3 Reducing the nutrient source

Europe is the continent that has suffered most from eutrophication, and increasing efforts are being made to restore European water bodies damaged by nutrient enrichment. If the ultimate goal is to restore sites where nature conservation interest has been damaged by eutrophication, techniques are required for reducing external loadings of nutrients into ecosystems.

Although algal production requires both nitrogen and phosphorus supplies, it is usually sufficient to reduce only one major nutrient. An analogy can be drawn with motor cars, which require lubricating oil, fuel and coolant to keep them moving and are likely to stop if they run short of any one of these, even if the other two are in plentiful supply. As phosphorus is the limiting nutrient in most freshwater systems, phosphorus has been the focus of particular attention in attempts to reduce inputs. In addition, nitrogen is less easily controlled: its compounds are highly soluble and can enter waterways from many diffuse sources. It can also be 'fixed' directly from the atmosphere. Phosphorus, on the other hand, is readily precipitated, usually enters water bodies from relatively few point sources (e.g. large livestock units or waste-water treatment works) and has no atmospheric reserve. However, efforts to reduce phosphorus loadings in some lakes have failed due to ongoing release of phosphorus from sediments. In situations where phosphorus has accumulated naturally (e.g. in areas with phosphate-rich rocks) and nitrogen increases have driven eutrophication, it may be necessary to control nitrogen instead.


Take your learning further371

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371