Use of different indices to assess the ecological status of lake systems in the eastern mediterranean river basin

The objective of this research was to assess the ecological status of lentic systems in the Eastern Mediterranean River basin (Türkiye) using some biotic (Q index, PT-BV, MedPTI, TDIL, and PTI) and abiotic (WQI, WQImin-nw, TSI, TLI, and Kna) indices. Phytoplankton species such as Peridinium cinctum, Ceratium hirundinella, and Gyrosigma balticum were the species that contributed the most to the algal biovolume of lake systems with different ecological statuses in the basin. According to the results, it was seen that CCA coordination, which analyzed the relationship structures between dominant phytoplankton taxa and environmental water quality parameters, explained the variation sufficiently. As pointed out in the CCA analysis, conductivity and ammonium were the main environmental parameters influencing algal assemblages at sampling sites in the basin (p < 0.01). Strong correlations were observed between TSI and TLI (correlation coefficient: 0.99), and TDIL showed significant correlation only with the Q index (p < 0.01). TSI, TLI and WQI, abiotic indices, indicated significant correlations with most environmental parameters (p < 0.01), while PTI, a biotic index, had weak correlations with most environmental parameters (p > 0.05). Among the indices used in this study, it seems that diatom-based TDIL and physicochemical-based WQI appear to be the most suitable indices for assessing the ecological status of lentic systems in the Mediterranean region. Accordingly, it can be deduced that coupling biotic and abiotic indices is more accurate in determining the water quality of lentic systems.