These nutrients are present in low concentrations in pristine water bodies to support life, however when the water becomes in enriched in N and P this can cause problems for the ecosystem and health of the area. The rough order of effects goes as follows:
1. Water bodies become unnaturally enriched in N and P (usually).
2. Unnaturally high rates of plant production (primary) result, as these nutrients are no longer limiting their growth. It is normally surface plants and particular types of algae that grow rapidly.
3. This results in algal surface blooms, preventing the sunlight from penetrating the water.
4. Plants beneath the surface cannot photosynthesis, die and are decomposed (mainly by bacteria).
5. The increased action by decomposers causes oxygen depletion from the water.
6. Lack of oxygen (and sometimes blooms of toxic species of algae) often cause the death of benthic organisms (e.g. invertebrates) and fish.
7. This ultimately results in a turbid, harsh system with low biodiversity - lacking in fish, multicelled plants and invertebrates, and algae-dominated. This gives the look of a 'green soup', which can be seen below.
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| Hungabee Lake (left), Canada; a healthy lake system. Lake Taihu (right) is a highly turbid, algae-dominated lake resulting from eutrophication. |
Eutrophication does take place as a natural process as sediments and organic matter accumulate. However, anthropogenic influences cause this to happen in a much more rapid timescale - the main source of nutrient flow into water bodies is nearby human settlements. Direct flows are increasingly common, taking the form of agricultural run-off from farm fertilisation and waste pipes. Increasing atmospheric pollution is even causing eutrophication in lakes at a great distance from any humans.
Currently this seems yet another way in which human utilisation of resources is damaging the environment and harming biodiversity, and many studies have been undertaken into the attempted recovery of these systems. The methods in which this has been attempted, and whether we even can repair the damage done will follow...
hey,
ReplyDeletewhat are the conservation methods that can prevent eutrophication? what do you think is the best method, taking everything into consideration e.g. cost effectiveness, suitability etc. Agricultural buffer zones are a widely accepted method of preventing eutrophication, do you think they work? can they be degraded over time, thus limiting their effectiveness?
cheers
Thanks for the comment.
ReplyDeleteI do believe, as I will go on to discuss in a later post, that prevention is the key to protecting water bodies from eutrophication.
Buffer zones, or Riparian buffers, have been shown to reduce nutrient load in water bodies, as they reduce agricultural run-off into streams - I do think these are one of the main ways we could prevent eutrophication. Similarly, establishing flood-plains for rivers also help prevent eutrophication, as nutrients are stripped away from the water before reaching still areas. Flood-plains particularly degrade overtime - these and buffer zones do have to be managed to keep being effective.
I think methods such as these are likely good preventative measures - maintaining these at rivers that act as a nutrient source to lakes, and diverting waste pipes from settlements away from water bodies are usually much more cost effective than having to deal with the consequences!