Responses of Phaeodactylum tricornutum to short-chain chlorinated paraffins: growth inhibition, photosynthetic damage and oxidative stress

IntroductionShort-chain chlorinated paraffins (SCCPs) have garnered increased attention due to higher persistence, bioaccumulation, long-distance transportation potential, and heightened toxicity to aquatic species and mammals.MethodsThis paper evaluated the toxic effects of SCCPs on P. tricornutum during a 96-hour acute exposure experiment, focusing on growth inhibition, photosynthetic parameters, and oxidative stress responses.ResultsResults showed that at the environmental concentration (0.001 mg/L), SCCPs exerted no significant effects on the growth and photosynthesis of P. tricornutum. However, higher concentrations (2, 4, and 8 mg/L) exposure resulted in a pronounced, dose-dependent growth inhibition, with inhibition rates reaching 37.43%, 53.25%, and 54.47% (p < 0.05), respectively. SCCPs stress disrupted the photosynthetic system, leading to reduction in the contents of chlorophyll a, chlorophyll c and carotenoids. Key photosynthetic pigments were depleted, and Photosystem II (PSII) efficiency (Fv/Fm, Y(II), rETRmax) was markedly suppressed. Furthermore, SCCPs exposure induced oxidative damage, as evidenced by elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Mitochondrial damage led to insufficient energy supply, resulting in decreased antioxidant enzyme activity.DiscussionCollectively, these findings establish that high concentrations of SCCPs inhibit algal growth and photosynthesis through a dual mechanism involving direct photosynthetic disruption and the induction of oxidative damage.