Polycyclic aromatic hydrocarbons (PAHs) are widespread pollutants in marine ecosystems including threatened and potentially sensitive coral reefs. Lower organisms such as phytoplankton, known to bioconcentrate PAHs, could serve as potential entry points for these chemicals into higher trophic levels. Here, we present a novel method using a ¹³C-labelled PAH and cavity ring-down spectroscopy (CRDS) to investigate accumulation, uptake rates and trophic transfer of PAHs in corals, which are key organisms to sustain biodiversity in tropical seas. We quantified the accumulation of ¹³C-phenanthrene in the marine microalga Dunaliella salina, and in the coral Acropora millepora after diffusive uptake from seawater or dietary uptake via labelled D. salina. Additionally, we monitored the photophysiological health of D. salina and A. millepora during phenanthrene exposure by pulse-amplitude modulation (PAM) fluorometry. Dose-dependent accumulation of ¹³C-phenanthrene in the microalga showed a mean bioconcentration factor (BCF) of 2590 ± 787 L kg⁻¹ dry weight. Corals accumulated phenanthrene from both exposure routes. While uptake of ¹³C-phenanthrene in corals was faster through aqueous exposure than dietary exposure, passive diffusion showed larger variability between individuals and both routes resulted in accumulation of similar concentrations of phenanthrene. The ¹³C-PAH labelling and analysis by CRDS proved to be a highly sensitive method. The use of stable isotopic label eliminated additional toxicity and risks by radioactive isotopic-labelling, and CRDS reduced the analytical complexity of PAH (less biomass, no extraction, fast analysis). The simultaneous, precise quantification of both carbon content and ¹³C/¹²C ratio (δ¹³C) enabled accurate determination of ¹³C-phenanthrene accumulation and uptake rate. This is the first study to provide empirical evidence for accumulation of phenanthrene in a phytoplankton-coral food chain.

多环芳烃（PAH）是海洋生态系统中广泛的污染物，包括受威胁的和潜在敏感的珊瑚礁。诸如浮游植物之类的低等生物可以生物富集多环芳烃，可以作为这些化学物质进入较高营养级的潜在切入点。在这里，我们介绍一种使用¹³ C标记的PAH和腔衰荡光谱（CRDS）的新颖方法，以研究珊瑚中PAHs的积累，吸收率和营养传递，这是在热带海洋中维持生物多样性的关键生物。我们量化了海洋微藻杜氏盐藻和珊瑚Acropora millepora中¹³ C-菲的积累从海水中扩散摄入或通过盐藻摄入的饮食。此外，我们通过脉冲幅度调制（PAM）荧光检测法监测了菲暴露过程中D. salina和A. millepora的光生理健康。藻类中¹³ C菲的剂量依赖性积累表明，其平均生物富集因子（BCF）为2590±787 L kg ^-1干重。珊瑚从两种暴露途径中积累了菲。同时吸收¹³通过水接触，珊瑚中的C-菲比通过食物接触要快，被动扩散显示个体之间的变异性更大，并且两种途径均导致相似浓度的菲积累。的¹³ C-PAH标记和分析由CRDS被证明是一个高度敏感的方法。稳定同位素标记物的使用通过放射性同位素标记物消除了其他毒性和风险，CRDS降低了PAH的分析复杂性（更少的生物量，无需提取，快速分析）。两者的碳含量和的同时，精确定量¹³ C / ¹² C之比（δ ¹³ C）使能准确测定¹³C-菲的积累和吸收率。这是第一项为菲在浮游植物-珊瑚食物链中积累菲提供经验证据的研究。