Eutrophication is a process of nutrient enrichment of a system and it is used to classify the stage at which this process is at any given time in a particular water body. The 'trophic status' of the water body is thus used as a description of the water quality status of water body, with regard to nutrient enrichment. The following classification terms and colour coding are used for easy reference.
| Oligotrophic | low in nutrients and not productive in terms of aquatic animal and plant life. |
| Mesotrophic | intermediate levels of nutrients, fairly productive in terms of aquatic animal and plant life and showing emerging signs of water quality problems. |
| Eutrophic | rich in nutrients, very productive in terms of aquatic animal and plant life and showing increasing signs of water quality problems. |
| Hypertrophic | very high nutrient concentrations where plant growth is determined by physical factors. Water quality problems are serious and can be continuous. |
Table 1. Method to determine trophic status statistics:
| Statistic | Unit | Current trophic status: | |||
|---|---|---|---|---|---|
| Mean annual chlorophyll a | µg/l | 0<x<10 | 10<x<20 | 20<x<30 | >30 |
| Oligotrophic
(low) |
Mesotrophic
(moderate) |
Eutrophic
(significant) |
Hypertrophic
(serious) |
||
| Current nuisance value of algal bloom productivity: | |||||
| % of time chlorophyll a> 30µg/l | % | 0 | 0<x<8 | 8<x<50 | >50 |
| negligible | moderate | significant | serious | ||
| Potential for algal and plant productivity: | |||||
| Mean annualTotal phosphorus | mg/l | x<0.015 | 0.015<x<0.047 | 0.047<x<0.130 | >0.130 |
| negligible | moderate | significant | serious | ||
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National Eutrophication Monitoring Programme site
Last edited 2011-10-18 12:26