Trophic level index

{{Short description|Measure of nutrient status of lakes}}

{{Use dmy dates|date=July 2019}}

{{Confuse|Trophic level}}

The trophic level index (TLI) is used in New Zealand as a measure of nutrient status of lakes.[http://www.mfe.govt.nz/environmental-reporting/freshwater/lake/trophic-level.html New Zealand Ministry for the Environment] {{Webarchive|url=https://web.archive.org/web/20100522140630/http://www.mfe.govt.nz/environmental-reporting/freshwater/lake/trophic-level.html |date=2010-05-22 }} - Trophic Level Index for lakes It is similar to the trophic state index but was proposed as alternative that suited New Zealand.{{cite book|last=Burns|first=Noel|author2=Graham Bryers |author3=Eddie Bowman |title=Protocol for Monitoring Trophic Levels of New Zealand Lakes and Reservoirs|date=March 2000|url=http://www.mfe.govt.nz/publications/fresh-water-environmental-reporting/protocol-monitoring-trophic-levels-new-zealand|accessdate=2017-05-09}}

The system uses four criteria, phosphorus and nitrogen concentrations, as well as visual clarity and algal biomass weighted equally.{{cite journal

| last1 = Burns | first1 = Noel

| last2 = McIntosh | first2 = John

| last3 = Scholes| first3 = Paul

| title = Strategies for Managing the Lakes of the Rotorua District, New Zealand

| journal = Lake and Reservoir Management

| volume = 21

| issue = 1

| pages = 61–72

| date = 2005

| doi = 10.1080/07438140509354413

| s2cid = 86767838

}}

class="wikitable"
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