Abstract：
Seaweeds are ecosystem engineers that can serve as habitat, sequester carbon, buffer ecosystems against acidification, and, in an aquaculture setting, represent an important food source. One health issue regarding the consumption of seaweeds and specifically, kelp, is the accumulation of some trace elements of concern within tissues. As atmospheric CO2 concentrations rise, and global oceans acidify, the concentrations of elements in seawater and kelp may change. Here, we cultivated the sugar kelp, Saccharina latissima under ambient (~400 μatm) and elevated pCO2 (600-2400 μatm) conditions and examined the accumulation of trace elements using x-ray powder diffraction, sub-micron resolution x-ray imaging, and inductively coupled plasma mass spectrometry. Exposure of S. latissima to higher concentrations of pCO2 and lower pH caused a significant increase (p < 0.05) in the iodine and arsenic content of kelp along with increased subcellular heterogeneity of these two elements as well as bromine. The iodine-to‑calcium and bromine-to‑calcium ratios of kelp also increased significantly under high CO2/low pH (p < 0.05). In contrast, high CO2/low pH significantly reduced levels of copper and cadmium in kelp tissue (p < 0.05) and there were significant inverse correlations between concentrations of pCO2 and concentrations of cadmium and copper in kelp (p < 0.05). Changes in copper and cadmium levels in kelp were counter to expected changes in their free ionic concentrations in seawater, suggesting that the influence of low pH on algal physiology was an important control on the elemental content of kelp. Collectively, these findings reveal the complex effects of ocean acidification on the elemental composition of seaweeds and indicate that the elemental content of seaweeds used as food must be carefully monitored as climate change accelerates this century.
摘要：
海藻是生态系统工程师，可以作为栖息地，固碳，缓冲生态系统免受酸化，and,在水产养殖环境中，是重要的食物来源。一个关于海藻消费的健康问题，特别是，海带,是组织内一些关注的微量元素的积累。随着大气中二氧化碳浓度的上升，全球海洋酸化，海水和海带中元素的浓度可能会发生变化。这里,我们种植了糖海带，在环境（〜400μatm）和升高的pCO2（600-2400μatm）条件下，并使用X射线粉末衍射检查了微量元素的积累，亚微米分辨率X射线成像，和电感耦合等离子体质谱。拉氏链球菌暴露于较高浓度的pCO2和较低的pH值会导致海带的碘和砷含量显着增加（p<0.05），同时这两种元素以及溴的亚细胞异质性增加。在高CO2/低pH下，海带的碘钙和溴钙比也显着增加（p<0.05）。相比之下,高CO2/低pH值显着降低海带组织中的铜和镉含量（p<0.05），pCO2浓度与海带中的镉和铜浓度之间存在显着负相关（p<0.05）。海带中铜和镉含量的变化与海水中自由离子浓度的预期变化相反，表明低pH对藻类生理的影响是对海带元素含量的重要控制。总的来说，这些发现揭示了海洋酸化对海藻元素组成的复杂影响，并表明随着本世纪气候变化的加速，必须仔细监测用作食物的海藻的元素含量。
