Objective Petroleum hydrocarbons have significant toxic effects on aquatic ecosystems, mainly manifested in the harm to marine life, impact on the photosynthesis of marine microalgae, and disruption of marine ecological balance. Skeletonema costatum is sensitive to toxic substances, easily obtainable, small in size, and reproduces quickly, allowing for the assessment of the impact of toxic substances on many generations and population levels of S. costatum in a short time, making it an excellent test organism. This study aims to investigate the changes in the proteomics of S. costatum under pollution stress caused by petroleum hydrocarbons.

Methods This study employed isobaric tag for relative and absolute quantitation (iTRAQ) in combination with reverse-phase liquid chromatography-mass spectrometry (RPLC-MS) to analyze the differential proteomic changes in S. costatum resulting from chronic and acute toxicity treatments with petroleum hydrocarbons.

Results Compared with the control group, 112 and 169 differentially expressed proteins (DEPs) were identified in the chronic and acute toxicity treatment groups, respectively, there were 40 overlapping DEPs between the two groups, with 20 of these proteins localized to the chloroplasts. The upregulated DEPs shared five common significantly enriched (P<0.05) gene ontology (GO) terms: carbohydrate derivative metabolic process, carbohydrate derivative biosynthetic process, inorganic diphosphatase activity, glutamine-fructose-6-phosphate transaminase (isomerization) activity, and carbohydrate derivative binding. However, there were no common significantly enriched pathways. The downregulated DEPs shared two common significantly enriched (P<0.05) GO terms: ATP hydrolysis coupled to proton transport and proton-translocating ATPase (V1 domain). Additionally, two common significantly enriched (P<0.05) pathways were identified: ductal acid secretion pathway and antibiotic biosynthesis pathway. The heat shock protein (protein ID: 220971590), which was related to toxicity response, was significantly upregulated (P<0.05) after chronic and acute toxicity treatments.

Conclusion The DEPs identified in Skeletonema costatum under petroleum hydrocarbon pollution stress are related to the stress response mechanisms of petroleum hydrocarbons. This study lays the foundation for understanding the toxicological mechanisms of petroleum hydrocarbons at the molecular level.