Toxicity screening of eight Prorocentrum lima (Dinophyceae) strains of coastal China

Diarrhetic shellfish poisoning, caused by Okadaic acid (OA) and its analogues, threatens nearshore ecosystems and public health. This study systematically compared eight Prorocentrum lima strains isolated from China’s coastal waters with respect to growth characteristics, toxin profiles and concentrations, toxin esterification status, and cytotoxicity. A multidimensional evaluation of toxin-producing potential and biological effects was conducted by integrating full-cycle culturing, LC–MS/MS analysis, and a Neuro-2a cell-based MTT bioassay. The results showed that OA and Diarrhetic shellfish toxin-1 (DTX-1) were detected in all strains, whereas DTX-2 was not detected. Total toxin levels measured after hydrolysis ranged from 17.07 to 31.84 pg OA-eq·cell − ¹, and esterification ratios differed markedly among strains (53.37%–93.07%), with strain 1115 exhibiting the highest ratio. Growth kinetics varied among strains, and a resource-allocation trade-off was observed between growth rate and toxin production. Cytotoxicity assays showed that toxicity increased with both concentration and exposure duration; overall, free toxin extracts were significantly more toxic than total toxin extracts ( p < 0.05), and toxic potency differed significantly among strains. OA-equivalent fitted concentrations back-calculated from the 24 h OA dose–response curve were generally higher than LC–MS/MS-measured concentrations, and fitted concentrations were significantly positively correlated with esterification ratios, suggesting that the contribution of esterified forms or their metabolites to overall toxicity may be underestimated by chemical analysis. In summary, P. lima exhibited pronounced intraspecific heterogeneity in toxin yield, chemotype, and biological effects. Integrating chemical analysis with cell-based bioassays enables a more comprehensive and accurate assessment of strain-associated ecological and public health risks.