This paper present the effects of ocean acidification on growth and domoic acid (DA) content of several strains of the toxic Pseudo-nitzschia australis and the non-toxic P. fraudulenta. Three strains of each species (plus two subclones of P. australis) were acclimated and grown in semi-continuous cultures at three pH levels: 8.07, 7.77, and 7.40, in order to simulate changes of seawater pH from present to plausible future levels. Our results showed that lowering pH from current level (8.07) to predicted pH level in 2100 (7.77) did not affect the mean growth rates of some of the P. australis strains (FR-PAU-17 and L3-100), but affected other strains either negatively (L3-30) or positively (L3.4). However, the growth rates significantly decreased with pH lowered to 7.40 (by 13% for L3-100, 43% for L3-30 and 16% for IFR-PAU-17 compared to the rates at pH 8.07). In contrast, growth rates of the non-toxic P. fraudulenta strains were not affected by pH changing from 8.07 to 7.40.

The P. australis strains produced DA at all pH levels tested, and the highest particulate DA concentration normalized to cell abundance (pDA) was found at pH 8.07. Total DA content (pDA and dissolved DA) was significantly higher at current pH (8.07) compared to pH (7.77), exept for one strain (L 3.4) where no difference was found. At lower pH levels 7.77 - 7.40, total DA content was similar, except for strains IFR-PAU-17 and L3-100 which had the lowest content at the pH 7.77. The diversity in the responses in growth and DA content highlights the inter- and intra-specific variation in Pseudo-nitzschia species in response to ocean acidification. When exploring environmental responses of Pseudo-nitzschia using cultured cells, not only strain-specific variation but also culturing history should be taken into consideration, as the light levels under which the subclones were cultured, afterwards affected both maximum growth rates and DA content.

本文介绍了海洋酸化对有毒Pseudo-nitzschia australis和无毒P.欺诈的几种菌株的生长和软骨藻酸 (DA) 含量的影响。每个物种的三个菌株（加上P. australis 的两个亚克隆）在三个 pH 水平：8.07、7.77 和 7.40 的半连续培养中适应和生长，以模拟海水 pH 从目前到可能的未来水平的变化。我们的结果表明，将 pH 从当前水平 (8.07) 降低到 2100 年的预测 pH 水平 (7.77) 不会影响某些澳大利亚松的平均增长率菌株（FR-PAU-17 和 L3-100），但对其他菌株产生负面影响（L3-30）或正面影响（L3.4）。然而，随着 pH 值降至 7.40，增长率显着下降（与 pH 值 8.07 的增长率相比，L3-100 的增长率为 13%，L3-30 为 43%，IFR-PAU-17 为 16%）。相比之下，无毒假单胞菌菌株的生长速率不受 pH 从 8.07 变为 7.40 的影响。

的芦苇菌株产生DA在所有测试的pH值水平，并归一化至细胞丰度（PDA）的最高颗粒DA浓度在pH 8.07被发现。与 pH (7.77) 相比，当前 pH (8.07) 下的总 DA 含量（pDA 和溶解的 DA）显着更高，但没有发现差异的一种菌株 (L 3.4) 除外。在 7.77 - 7.40 的较低 pH 水平下，总 DA 含量相似，但菌株 IFR-PAU-17 和 L3-100 在 pH 7.77 时的含量最低。生长和 DA 含量响应的多样性突出了Pseudo-nitzschia物种响应海洋酸化的种间和种内变化。在探索Pseudo-nitzschia 的环境反应时 使用培养细胞时，不仅应考虑菌株特异性变异，还应考虑培养历史，因为培养亚克隆的光照水平会影响最大生长速率和 DA 含量。