Despite widespread metal pollution of coastal ecosystems, little is known of its effect on marine phytoplankton. We designed a co-cultivation experiment to test if toxic dose–response relationships can be used to predict the competitive outcome of two species under metal stress. Specifically, we took into account intraspecific strain variation and selection. We used 72 h dose–response relationships to model how silver (Ag), cadmium (Cd), and copper (Cu) affect both intraspecific strain selection and competition between taxa in two marine diatoms (Skeletonema marinoi and Thalassiosira baltica). The models were validated against 10-day co-culture experiments, using four strains per species. In the control treatment, we could predict the outcome using strain-specific growth rates, suggesting low levels of competitive interactions between the species. Our models correctly predicted which species would gain a competitive advantage under toxic stress. However, the absolute inhibition levels were confounded by the development of chronic toxic stress, resulting in a higher long-term inhibition by Cd and Cu. We failed to detect species differences in average Cu tolerance, but the model accounting for strain selection accurately predicted a competitive advantage for T. baltica. Our findings demonstrate the importance of incorporating multiple strains when determining traits and when performing microbial competition experiments.

尽管沿海生态系统普遍存在金属污染，但人们对其对海洋浮游植物的影响知之甚少。我们设计了一个共培养实验来测试毒性剂量反应关系是否可用于预测两个物种在金属压力下的竞争结果。具体来说，我们考虑了种内菌株的变异和选择。我们使用 72 小时剂量反应关系来模拟银 (Ag)、镉 (Cd) 和铜 (Cu) 如何影响两种海洋硅藻（Skeletonema marinoi和Thalassiosira baltica ）中的种内菌株选择和分类群之间的竞争）。这些模型针对 10 天的共培养实验进行了验证，每个物种使用四个菌株。在对照处理中，我们可以使用特定菌株的生长速率来预测结果，这表明物种之间存在低水平的竞争性相互作用。我们的模型正确地预测了哪些物种将在有毒压力下获得竞争优势。然而，慢性毒性应激的发展混淆了绝对抑制水平，导致 Cd 和 Cu 的长期抑制作用更高。我们未能检测到平均铜耐受性的物种差异，但考虑菌株选择的模型准确地预测了T. baltica的竞争优势. 我们的研究结果证明了在确定性状和进行微生物竞争实验时结合多种菌株的重要性。