{{Short description|Measure of nutrient status of lakes}} {{Use dmy dates|date=July 2019}} {{Distinguish|Trophic level}} The '''trophic level index''' (TLI) is used in New Zealand as a measure of nutrient status of lakes.<ref>[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</ref> It is similar to the trophic state index but was proposed as alternative that suited New Zealand.<ref>{{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=https://www.mfe.govt.nz/publications/fresh-water-environmental-reporting/protocol-monitoring-trophic-levels-new-zealand|accessdate=2017-05-09}}</ref>
The system uses four criteria, phosphorus and nitrogen concentrations, as well as visual clarity and algal biomass weighted equally.<ref>{{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 }}</ref>
{| class="wikitable" |- ! Lake type !! Trophic level !! Chla (mg m<sup>−3</sup>) !! Secchi depth (m) !! TP (mg P m<sup>−3</sup>) !! TN (mg N m<sup>−3</sup>) |- | 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== *[http://www.mfe.govt.nz/more/environmental-reporting/fresh-water/lake-water-quality-indicator/water-quality-indicators-lakes New Zealand Ministry for the Environment] - Trophic Level Index for lakes *[http://www.waikatoregion.govt.nz/Environment/Natural-resources/Water/Lakes/ Definitions of the 5 trophic states - Oligotrophic, Mesotrophic, Eutrophic, Supertrophic and Hypertrophic lakes]
==References== {{Reflist}}
Category:Water in New Zealand Category:Water pollution
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