Trophic level index

Not to be confused with Trophic level.

The trophic level index (TLI) is used in New Zealand as a measure of nutrient status of lakes.^[1] It is similar to the trophic state index but was proposed as alternative that suited New Zealand.^[2]

The system uses four criteria, phosphorus and nitrogen concentrations, as well as visual clarity and algal biomass weighted equally.^[3]

Lake type	Trophic level	Chla (mg m−3)	Secchi depth (m)	TP (mg P m−3)	TN (mg N m−3)
Ultra-microtrophic	0-1	0.13-0.33	31-24	0.84-1.8	16-34
Microtrophic	1-2	0.33-0.82	24-15	1.8-4.1	34-73
Oligotrophic	2-3	0.82-2.0	15-7.8	4.1-9.0	73-157
Mesotrophic	3-4	2.0-5.0	7.8-3.6	9.0-20	157-337
Eutrophic	4-5	5.0-12	3.6-1.6	20-43	337-725
Supertrophic	5-6	12-31	1.6-0.7	43-96	725-1558
Hypertrophic	6-7	>31	<0.7	>96	>1558

See also

• Water pollution in New Zealand
• Lakes of New Zealand
• Environment of New Zealand

External links

• New Zealand Ministry for the Environment - Trophic Level Index for lakes
• Definitions of the 5 trophic states - Oligotrophic, Mesotrophic, Eutrophic, Supertrophic and Hypertrophic lakes