| Title |
Suggestion for Trophic State Index of Korean Lakes (Upper Layer) |
| Authors |
공동수 ( Dongsoo Kong ) ; 김범철 ( Bomchul Kim ) |
| DOI |
https://doi.org/10.15681/KSWE.2019.35.4.340 |
| Keywords |
Eutrophication; Trophic state classification; Trophic state index; Water quality |
| Abstract |
In this study, the relationship between trophic state indices was analyzed based on the monthly or weekly water quality data of 81 lakes (mostly man-made) in Korea between 2013-2017. Carlson’s TSIC and Aizaki’s TSIm were calculated using the summer (Jun.-Sep.) average data at the upper water layer. The previous Korean trophic state index (TSIKO) and the newly suggested index (TSIKON) was calculated using the annual average data at the whole layer and at the upper layer, respectively. While previous trophic state index (TSI) such as Carlson’s TSI included logarithmic function, we devised newly Monod-type TSIKON(Chl) that is 50 when half-saturation concentration of chlorophyll α (Chl.α) measured by UNESCO-method is 10 μg L-1. MMF-type TSIKON(TP) was derived based on the relationship between TP and Chl.α. A comprehensive TSIKON was decided as the larger one of the two TSIKON values. The range of previous TSI was usually 40-50 for the mesotrophic state, which seemed narrow to discriminate trophic characteristics of the class. The upper limits of TSIKON for oligotrophic, mesotrophic, and eutrophic state were set to 23, 50 and 75, respectively. Classification by TSIC and TSIm showed higher frequency of eutrophic class compared to TSIKO and TSIKON. This means that the estimation by TSIs developed in foreign natural lakes can lead to distorted results in the classification of the trophic state of Korean lakes. This is due to the decrease of transparency by non-algal material and the reduction in phosphorus availability to algal growth, particularly in Monsoon period. |