With carbon dioxide (CO₂) levels rising dramatically, climate change threatens marine environments. Due to increasing CO₂ concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. Living in intertidal environments, hermit crabs face large pH fluctuations in their current habitat in addition to climate-change related ocean acidification. We demonstrate that the dietary predator cue PEA for mammals and sea lampreys is an attractant for hermit crabs, with the potency of the cue increasing with decreasing pH levels. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH-dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.

随着二氧化碳（CO ₂）水平急剧上升，气候变化威胁着海洋环境。由于海洋中 CO ₂浓度的增加，预计到本世纪末，pH 值将下降 0.4 个单位。迫切需要了解海洋酸化对化学生态过程的影响。迄今为止，海洋 pH 值降低影响化学通讯的程度和机制尚不清楚。我们将行为分析与计算化学相结合，探索捕食者相关线索 2-苯乙胺 (PEA) 对寄居蟹 ( Pagurus bernhardus ) 的作用) 在当前和本世纪末的海洋 pH 值中。生活在潮间带环境中的寄居蟹除了与气候变化相关的海洋酸化外，还面临其当前栖息地的巨大 pH 值波动。我们证明了哺乳动物和海七鳃鳗的饮食捕食者提示 PEA 是寄居蟹的引诱剂，提示的效力随着 pH 值的降低而增加。为了解释这种增加的效力，我们评估了 PEA 的构象和电荷相关特性的变化作为一种​​潜在的机制途径。使用核磁共振光谱验证的量子化学计算，我们表征了水中 PEA 的不同质子化状态。我们使用可能的 PEA 模型受体（人类 TAAR1）展示了 PEA 的质子化如何影响受体-配体结合。