A Phytoplankton Composition Index Response to Eutrophication in Turkish Lakes and Reservoirs

Turkiye is surrounded on three sides by the Mediterranean, Aegean, Marmara, and Black Seas. It has a high biodiversity due to its location between the continents of Europe and Asia. The findings of recent monitoring studies conducted under the Water Framework Directive have revealed this diversity. Thus, the concept of developing a new lake phytoplankton composition index has evolved. This study analyzed the results of 2650 phytoplankton samples collected from 491 lakes and reservoirs that were monitored by the T.R. Ministry of Agriculture and Forestry, Directorate General of Water Management. The index used a total of 165 phytoplankton genera. In this context, the PHYTO-TR composition index was developed by analyzing phytoplankton species' responses to total phosphorus. As a result of the study, the PHYTO-TR and total phosphorus results of the lakes were regressed (R-2 = 0.4081, p < 0.01). Due to the good correlation with total phosphorus, the PHYTO-TR index is regarded as an appropriate instrument for routine phytoplankton assessment according to the Water Framework Directive. Its performance on a larger scale should be evaluated based on its applications in neighboring European and Asian countries.