Polar cod early life stage exposure to potential oil spills in the Arctic Aquatic Toxicology

Arctic amplification of climate change is causing sea ice to retreat at unprecedented rates, potentially opening up large vulnerable Arctic areas for oil and gas exploration and new shipping routes. This rapid warming marginalizes sympagic species habitats making them more sensitive to other anthropogenic pressures. Here, we assess potential impacts of hypothetic oil spills from the northernmost licensed oil field Wisting and additional neighbouring spill sites in areas currently not open to oil exploitation on the key ice-associated Arctic fish species polar cod (Boreogadus saida). We do this by developing and running combined data-driven models for the ocean, oil spill dispersal and fate, and the early life stages of polar cod. Sea ice and the Polar Front act as natural barriers limiting the exchange of polar cod eggs and larvae and oil spill between Atlantic and Polar Water. However, both barriers vary seasonally so that the sea ice retreats and the Polar Front weakens towards summer causing significant increases in oil exposure to early life stages of polar cod under varying oil spill scenarios investigated here. Previous literature emphasizes that fall feeding conditions must be sufficient for juvenile polar cod to allocate lipids and survive their first winter. Here, we show that less than half the exposed individuals experience these suitable feeding conditions in the fall. The seasonal exposure intensity suggests a need for petroleum regulations with temporal and spatial limitations varying through the year. However, even with these seasonal dynamic regulations in place, climate change induced by the use of fossil fuel will likely reduce these natural barriers through continued sea ice retreat and a weakening of the Polar Front thereby reducing their barrier effects. Risk assessments of anthropogenic impacts on key Arctic ecosystem components in the vicinity of the ice edge zone and the Polar Front will therefore have to be updated to account for these major changes.

气候变化的北极放大效应（Arctic amplification）正导致海冰以史无前例的速度消退，或为油气勘探开辟大片脆弱北极海域，并催生新的航运航线。此种快速升温将挤压冰源生物的栖息地，使其对其他人为活动压力更为敏感。本研究针对最北端获批油田维斯廷（Wisting）以及当前尚未开放油气开发的邻近假想溢油点位，评估其对关键冰栖北极鱼类——极地鳕鱼（Boreogadus saida）的潜在影响。为此，我们开发并运行了耦合的数据驱动模型，用于模拟海洋环境、溢油扩散与归宿，以及极地鳕鱼的早期生命阶段。海冰与极锋（Polar Front）作为天然屏障，限制了极地鳕鱼卵、幼体与溢油在大西洋水与极地水之间的交换。但两类屏障均随季节动态变化：夏季海冰消退、极锋减弱，会导致本研究考察的各类溢油情景下，极地鳕鱼早期生命阶段面临的溢油暴露显著提升。既往研究指出，秋季摄食条件必须足够充足，才能让幼年极地鳕鱼积累脂质并顺利度过首个冬季。本研究结果显示，仅有不足半数的暴露个体能在秋季获得适宜的摄食条件。季节性暴露强度表明，需制定随时间与空间动态调整的石油行业监管规范。然而，即便落实此类季节性动态监管，化石燃料使用引发的气候变化仍将通过持续海冰消退与极锋减弱，削弱上述天然屏障的阻隔作用。因此，亟需更新针对冰缘带与极锋周边区域关键北极生态系统组分的人为影响风险评估，以纳入这些重大变化。