Evaluation of morphological and physiological effects of pile driving noise on marine microalgae using flow cytometry and pulse-amplitude modulated fluorometry

Pile driving noise has emerged as a major anthropogenic stressor in marine ecosystems, yet its effects on microalgae remain largely unexplored. This study investigated the morphological and physiological responses of three marine microalgae species (Isochrysis galbana, Dunaliella tertiolecta, and Phaeodactylum tricornutum) to simulated pile driving noise. The analysis included assessments of growth inhibition, changes in cell size, granularity, esterase activity, membrane permeability, and photosynthetic activity, using flow cytometry and pulse-amplitude modulated fluorometry. All species exhibited significant reductions in cell size and granularity following noise exposure, with esterase activity being the most affected endpoint. Meanwhile, I. galbana exhibited a selective survival strategy, while D. tertiolecta and P. tricornutum employed physiological adjustments and structural adaptation. Among the species, P. tricornutum showed the highest sensitivity and slowest recovery to noise exposure. These findings emphasize the importance of multiple indicators beyond cell density for evaluating noise-induced stress in microalgae and provide insights into the ecological impact of underwater noise pollution on primary producers.