Combined evaluation of physicochemical parameters and<i> Daphnia</i><i> magna</i> toxicity tests of Gediz River surface water

In this study, pollution in the Gediz River was assessed using Daphnia magna toxicity tests. Water samples were collected from five distinct stations during spring and summer. Concentrations of key chemical constituents, including Fe, Mn, Cl-, NH3-N, S2-, K, NO3--N, and PO43-, were determined spectrophotometrically. Acute and chronic toxicity tests were conducted according to OECD guidelines. Acute toxicity was observed at multiple stations in spring and at one station in summer. Conversely, chronic exposure results revealed no significant adverse effects on D. magna, despite the known organic and inorganic pollution in the Gediz River. Interestingly, some samples demonstrated stimulation of growth, development, and reproduction in the test organisms, indicating hormetic effects caused by low pollutant concentrations in the water, which are more concentrated in sediments. These findings underscore that Daphnia-based water-column toxicity tests alone may not fully capture the combined impacts of organic and inorganic contaminants present in the Gediz River.