refer to the depletion of oxygen levels in a water body, which may or may not cause the death of aquatic organisms. It occurs when high levels of nutrients – often phosphates or nitrates – are introduced into the aquatic environment. This causes the rapid growth of algae and other plants. When these die, they decay: a process which rapidly removes oxygen from the water¹.
Probably the best known examples of eutrophication are the large fish kills which occur from time to time in various water bodies around the world. Usually these are the result of ‘algae blooms’, or a quick increase in the amount of phytoplankton present in the water. Human induced, or cultural eutrophication, is usually due to the discharge of fertilizers, sewage, or detergents which contain high levels of phosphates¹. There are a number of things that you can do to prevent eutrophication if you care about the environment, including:
Reducing the nutrient load on water bodies
The best, easiest, and most efficient way to prevent eutrophication is by preventing excess nutrients from reaching water bodies. This can be done in a number of ways, the simplest of which is just being aware of the chemicals and fertilizers that we are using.
If you want (or need) to fertilize your garden or fields, fine, that’s ok. However, do it at the right time and don’t over fertilize. If you put your fertilizer on just before a big rain storm, then most of it will be lost and will probably end up in the nearest waterway (due to runoff). In the same way, if you put too much fertilizer on then some of it will not be bound to the soil. This means that it is just ‘floating’ around waiting for the next shower of rain to wash it into a river or lake².
We can also reduce the nutrient load due to sewage disposal by stopping our expulsion of it directly into waterways. In developed countries this is a relatively minor problem, but many poor areas still release untreated human waste directly into rivers³.
Once more, the easiest way of stopping excess phosphates associated with detergents entering waterways is by stopping the detergent itself entering the waterway. How do we do this? By not using them at all! There are many alternative products on the market which don’t contain phosphates or other nutrients, but which work just as well as traditional ones.
Creating Riparian Buffers
Nutrient runoff is going to happen no matter how careful we are and how much we educate people. One of the best ways to prevent this runoff having nasty side effects is by creating Riparian Buffers. A Riparian Buffer is a vegetated area between a river or lake and the land that is in use. It is designed to trap the phosphorus and nitrogen dissolved in water moving through it. One study found that the use of these zones trapped up to 97% of these nutrients before they reached the waterbody⁴.
Being Careful in Your Garden!
By being aware of the effects of your gardening practices and the way in which they can contribute to eutrophication, you can do whatever you need to to reduce your impact. As mentioned above, the smart application of fertilizer is one thing which you can ensure that you do. You can also do things like only watering where necessary, preventing excess water flowing away from your garden, and reducing sprinkler usage. Using a sprinkler usually creates a lot of water runoff which effectively carries nutrients away from your garden towards the nearest drain or waterway⁵.