Institute for Conservation Research, San Diego Zoo Global, San Diego, CA 92027, USA
University of California, Santa Cruz, Department of Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA.
J Exp Biol. 2021 Feb 24;224(Pt Suppl 1):jeb228049. doi: 10.1242/jeb.228049.
Rapid environmental changes in the Arctic are threatening the survival of marine species that rely on the predictable presence of the sea ice. Two Arctic marine mammal specialists, the polar bear () and narwhal (), appear especially vulnerable to the speed and capriciousness of sea ice deterioration as a consequence of their unique hunting behaviors and diet, as well as their physiological adaptations for slow-aerobic exercise. These intrinsic characteristics limit the ability of these species to respond to extrinsic threats associated with environmental change and increased industrial activity in a warming Arctic. In assessing how sea ice loss may differentially affect polar bears that hunt on the ice surface and narwhals that hunt at extreme depths below, we found that major ice loss translated into elevated locomotor costs that range from 3- to 4-fold greater than expected for both species. For polar bears this instigates an energy imbalance from the combined effects of reduced caloric intake and increased energy expenditure. For narwhals, high locomotor costs during diving increase the risk of ice entrapment due to the unreliability of breathing holes. These species-specific physiological constraints and extreme reliance on the polar sea ice conspire to make these two marine mammal specialists sentinels of climate change within the Arctic marine ecosystem that may foreshadow rapid changes to the marine ecosystem.
北极地区环境的快速变化正威胁着依赖海冰稳定存在的海洋物种的生存。两位北极海洋哺乳动物专家，北极熊和独角鲸，由于其独特的捕猎行为和饮食方式，以及适应缓慢有氧运动的生理特性，在海冰恶化的速度和无常性方面显得尤为脆弱。这些内在特征限制了这些物种应对与环境变化和北极变暖相关的工业活动增加相关的外在威胁的能力。在评估海冰减少如何对在冰面上捕猎的北极熊和在深海下捕猎的独角鲸产生不同影响时，我们发现，主要的海冰减少导致两种物种的运动成本增加了 3 到 4 倍。对于北极熊来说，这会导致由于热量摄入减少和能量消耗增加而产生的能量失衡。对于独角鲸来说，潜水时的高运动成本增加了因呼吸孔不可靠而被困在冰中的风险。这些物种特有的生理限制和对极地海冰的极端依赖，使得这两种海洋哺乳动物专家成为北极海洋生态系统中气候变化的哨兵，这可能预示着海洋生态系统的快速变化。
