The first eco-assessment of phytoplankton assemblages associated with environmental conditions of different lakes in the Western Black Sea basin of Türkiye

Lakes play a vital role in supporting biodiversity, providing water resources, regulating climate, cycling nutrients, and offering recreational opportunities. Despite their importance for environmental health and human well-being, lakes face significant pressures in the Anthropocene era. The present work seeks to assess the species-environment interactions and the ecological status of six lakes in the Western Black Sea basin of Türkiye utilizing phytoplankton metrics during wet and dry periods. Canonical correspondence analysis revealed a significant correlation equal to 98.5% between phytoplankton species and environmental stressors during two hydrological periods. Electrical conductivity (EC), pH, total organic carbon (TOC), and temperature were the most influential environmental factors affecting phytoplankton distribution in lakes (p = 0.002). Lake Sarıkum, a brackish habitat, was under high EC and pH pressure and is characterized by pollution-tolerant species. Lake Yeniçağa associated with TOC is characterized by some species, such as Anabaenopsis milleri, Chroococcus turgidus, Pseudoschroederia robusta, Aphanocapsa sp., Merismopedia glauca, Micractinium quadrisetum, and Microcystis aeruginosa. Lake Abant is located on the opposite side of EC, TOC, and temperature, which was associated with some species such as Cymbella affinis, Achnanthidium minutissimum, Encyonema minutum, E. silesiacum, and Dinobryon divergens. Results of the phyto-assessment displayed that the ecological status (ES) of the sampling stations during the rainy and dry periods varied from bad to high. The modified phytoplankton trophic index (MPTI) exhibited that a moderate ES was found in Lakes Sarıkum and Yeniçağa, while others had a good ES. The present study confirmed that phytoplankton communities are strongly linked to the ecological status of lakes in the Western Black Sea basin, which could be assessed using the MPTI.