New findings from the first fish toxicity test conducted following the algal bloom of Polykrikos hartmannii (Dinophyceae) in the Bay of Izmir, Aegean Sea
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The excessive proliferation of harmful algae can lead to fish mortality in coastal ecosystems. This study presents the results of a toxicity test conducted in response to the excessive proliferation of the species Polykrikos hartmannii in the Inner Bay of Izmir. The experiment used Sparus aurata that were exposed for 120 hours to a 100% concentration (2.4 x 10³ ± 0.090 cells·mL-¹) determined based on the cell density in nature, and to dilutions of this concentration at 50%, 25% and 12.5%. A control group was also included in the study. In addition to mortality, fish behaviour was observed. Based on the results, no mortality was recorded at any concentration, and behaviour remained normal. Although P. hartmannii has been reported as ichthyotoxic in the literature, the current findings suggest that the toxic effect of the species may be associated with environmental conditions and feeding strategy (mixotrophic feeding).
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