The combined effects of polycyclic aromatic hydrocarbons and seawater acidification are poorly understood. Hence, we exposed the bloom-forming diatom Skeletonema costatum to four concentrations (0, 0.1, 1 and 10 μg L^-1) of benzo(a)pyrene and two pCO₂ levels (400 and 1000 μatm) to investigate its physiological performance. The growth and photosynthesis of S. costatum were tolerant to low and moderate benzo(a)pyrene concentrations regardless of the pCO₂ level. However, the highest benzo(a)pyrene concentration had remarkably adverse effects on most parameters, decreasing the growth rate by 69%. Seawater acidification increased the sensitivity to high light stress, as shown by the lower relative maximum electron transport rate and light saturation point at the highest benzo(a)pyrene concentration. Our results suggested that benzo(a)pyrene could be detrimental to diatoms at a habitat-relevant level, and seawater acidification might further decrease its light tolerance, which would have important ramifications for the community structure and primary production in coastal waters.

人们对多环芳烃和海水酸化的综合影响知之甚少。因此，我们将形成水华的硅藻Skeletonema costatum暴露于四种浓度（0、0.1、1和 10 μg L ^-1）的苯并 (a) 芘和两种 pCO ₂水平（400 和 1000 μatm）以研究其生理性能。无论 pCO ₂浓度如何，S. costatum的生长和光合作用都能耐受低浓度和中等浓度的苯并 (a) 芘等级。然而，最高的苯并 (a) 芘浓度对大多数参数产生了显着的不利影响，使增长率降低了 69%。海水酸化增加了对高光应力的敏感性，如苯并（a）芘浓度最高时相对最大电子传输速率和光饱和点较低所示。我们的研究结果表明，苯并 (a) 芘可能在栖息地相关水平上对硅藻有害，海水酸化可能会进一步降低其耐光性，这将对沿海水域的群落结构和初级生产产生重要影响。