Ecotoxicological effects of suspended sediments on marine microalgae using flow cytometry and pulse-amplitude modulation (PAM) fluorometry

Microalgal bioassays were conducted to evaluate the ecotoxicological effects of suspended sediments (SS) collected from coastal environments. Growth inhibition was assessed for six microalgal species, and multiple endpoints were measured using flow cytometry (FCM) and pulse-amplitude modulation (PAM) fluorometry for three species (Dunaliella tertiolecta, Isochrysis galbana, and Phaeodactylum tricornutum). Among these, the EC50 for growth inhibition of D. tertiolecta (6700 mg L-1) was notably lower compared to the other species, and among several endpoints, esterase activity was the most inhibited. Species-specific responses to SS exposure were identified, with D. tertiolecta exhibiting greater susceptibility across most endpoints. Meanwhile, measurements of Fo', Fm', and Y(NPQ) in P. tricornutum using PAM fluorometry revealed greater sensitivity. Based on the results of this study and review, the tentative predicted no-effect concentration was calculated as 12.1 mg L-1. Overall, this study provides novel insights into SS ecotoxicity, establishing a crucial baseline for future investigations.