Seawater carbonate chemistry and the Gd bioaccumulation and oxidative stress-related responses of the surf clam Spisula solida

Humans have exhaustively combusted fossil fuels, and released pollutants into the environment, at continuously faster rates resulting in global average temperature increase and seawater pH decrease. Climate change is forecasted to exacerbate the effects of pollutants such as the emergent rare earth elements. Therefore, the objective of this study was to assess the combined effects of rising temperature (delta = + 4 °C) and decreasing pH (delta = − 0.4 pH units) on the bioaccumulation and elimination of gadolinium (Gd) in the bioindicator bivalve species Spisula solida (Surf clam). We exposed surf clams to 10 µg/L of GdCl3 for seven days, under warming, acidification, and their combination, followed by a depuration phase lasting for another 7 days and investigated the Gd bioaccumulation and oxidative stress-related responses after 1, 3 and 7 days of exposure and the elimination phase. Gadolinium accumulated after just one day with values reaching the highest after 7 days. Gadolinium was not eliminated after 7 days, and elimination is further hampered under climate change scenarios. Warming and acidification, and their interaction did not significantly impact Gd concentration. However, there was a significant interaction on clam's biochemical response. The augmented total antioxidant capacity and lipid peroxidation values show that the significant impacts of Gd on the oxidative stress response are enhanced under warming while the increased superoxide dismutase and catalase values demonstrate the combined impact of Gd, warming & acidification. Ultimately, lipid damage was greater in clams exposed to warming & Gd, which emphasizes the enhanced toxic effects of Gd in a changing ocean.

人类持续以不断加快的速率耗尽化石燃料并向环境排放污染物，由此引发全球平均气温上升与海水pH值下降。据预测，气候变化会加剧新兴稀土元素等污染物的生态影响。因此，本研究旨在评估气温上升（变化量Δ=+4℃）与海水pH降低（变化量Δ=-0.4 pH单位）的复合效应，及其对生物指示种双壳类——沙海螂（Spisula solida, Surf clam）体内钆（Gadolinium, Gd）的生物富集（bioaccumulation）与消除过程的影响。我们将沙海螂置于10 μg/L的三氯化钆（Gadolinium Trichloride, GdCl3）溶液中，分别在升温、酸化以及二者复合的环境条件下暴露7天，随后开展为期7天的净化（depuration）阶段；并在暴露1、3、7天以及净化阶段后，检测钆的生物富集水平与氧化应激（oxidative stress）相关响应指标。钆仅在暴露1天后即发生富集，并于第7天达到富集峰值。暴露7天后未检测到钆的消除，且在气候变化情景下，钆的消除过程会进一步受阻。升温与酸化及其交互作用对钆的体内浓度无显著影响。但二者的交互作用对沙海螂的生化响应存在显著影响。总抗氧化能力（total antioxidant capacity）与脂质过氧化（lipid peroxidation）水平的升高表明，升温条件下钆对氧化应激响应的显著影响被增强；而超氧化物歧化酶（superoxide dismutase, SOD）与过氧化氢酶（catalase, CAT）活性的提升则体现了钆、升温与酸化三者的复合效应。最终，在升温与钆共同暴露的沙海螂体内，脂质损伤更为严重，这表明在不断变化的海洋环境中，钆的毒性效应被进一步增强。