Allelochemical induces growth and photosynthesis inhibition, oxidative damage in marine diatom Phaeodactylum tricornutum

• HQ had high inhibitory effects on marine microalgae P. tricornutum.
• HQ exposure results in the changes of the ratio of carotenoids and Chlorophyll a.
• HQ induced oxidative stress in P. tricornutum.
• HQ altered the permeability of cell membrane and mitochondrial membrane potential.
• HQ inhibited the transcription of photosynthesis and respiration related genes.

Algal blooms have been occurring in many regions all over the world and allelochemical is considered as one of the important and promising algaecides to control algal blooms. In the present study, we investigated the effects of allelochemical hydroquinone (HQ) on growth, photosynthesis and other physiological levels of Phaeodactylum tricornutum (P. tricornutum). The results showed that HQ (above 3 × 10− 7 mol/L) significantly inhibited the growth and specific growth rate of algae. EC50 values were calculated at four different incubation times, i.e. 24, 48, 72 and 96 h. EC50 values increased with the treated-time increasing, which suggested that HQ stress on the algae gradually weakened with time prolonging. The contents of cellular pigments including Chlorophyll a (Chl.a) and carotenoids were significantly decreased by HQ. However, the ratios of carotenoids to Chl.a increased obviously when algae were exposed to 6 and 7 × 10− 7 mol/L of HQ for 72 h, which implied that the ratios of pigments changed in extreme conditions to resist environmental stress. At the same time, HQ also induced the responses of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST) and non-enzymatic antioxidant reduced glutathione (GSH). Additionally, flow cytometric assays showed that HQ stress altered the permeability of cell membrane and mitochondrial membrane potential in different degrees and HQ significantly inhibited the transcription of photosynthesis and respiration related genes. All these results showed that HQ might have the potential as an algaecide to control marine microalgae.