Greenland Institute of Natural Resources, Strandgade 91, 1401, Copenhagen, Denmark.
Greeneridge Sciences, Inc, 5266 Hollister Avenue, Suite 107, Santa Barbara, CA, 93111, USA.
Sci Rep. 2020 Oct 29;10(1):18678. doi: 10.1038/s41598-020-75658-6.
Arctic top predators are expected to be impacted by increasing temperatures associated with climate change, but the relationship between increasing sea temperatures and population dynamics of Arctic cetaceans remains largely unexplored. Narwhals (Monodon monoceros) are considered to be among the most sensitive of Arctic endemic marine mammals to climate change due to their limited prey selection, strict migratory patterns and high site fidelity. In the context of climate change, we assume that the population dynamics of narwhals are partly influenced by changes in environmental conditions, with warm areas of increasing sea temperatures having lower abundance of narwhals. Using a unique large dataset of 144 satellite tracked narwhals, sea surface temperature (SST) data spanning 25 years (1993-2018) and narwhal abundance estimates from 17 localities, we (1) assessed the thermal exposure of this species, (2) investigated the SST trends at the summer foraging grounds, and (3) assessed the relationship between SST and abundance of narwhals. We showed a sharp SST increase in Northwest, Mideast and Southeast Greenland, whereas no change could be detected in the Canadian Arctic Archipelago (CAA) and in the Greenland Sea. The rising sea temperatures were correlated with the smallest narwhal abundance observed in the Mideast and Southeast Greenland (< 2000 individuals), where the mean summer sea temperatures were the highest (6.3 °C) compared to the cold waters of the CAA (0.7 °C) that were associated with the largest narwhal populations (> 40,000 individuals). These results support the hypothesis that warming ocean waters will restrict the habitat range of the narwhal, further suggesting that narwhals from Mideast and Southeast Greenland may be under pressure to abandon their traditional habitats due to ocean warming, and consequently either migrate further North or locally go extinct.
北极顶级捕食者预计将受到与气候变化相关的温度升高的影响，但海洋温度升高与北极鲸目动物种群动态之间的关系在很大程度上仍未得到探索。独角鲸 (Monodon monoceros) 由于其有限的猎物选择、严格的迁徙模式和高度的栖息地忠诚度，被认为是对气候变化最敏感的北极特有海洋哺乳动物之一。在气候变化的背景下，我们假设独角鲸的种群动态部分受到环境条件变化的影响，温暖地区的海洋温度升高会导致独角鲸数量减少。利用一个独特的大型独角鲸卫星追踪数据集，涵盖了 25 年（1993-2018 年）的海表温度 (SST) 数据和 17 个地点的独角鲸数量估计，我们 (1) 评估了该物种的热暴露情况，(2) 调查了夏季觅食地的 SST 趋势，以及 (3) 评估了 SST 与独角鲸数量之间的关系。我们发现，西北、中东和东南格陵兰的 SST 急剧上升，而加拿大北极群岛 (CAA) 和格陵兰海则没有变化。不断上升的海水温度与在中东和东南格陵兰观察到的最小独角鲸数量有关 (<2000 头)，那里的夏季平均海水温度最高 (6.3°C)，而 CAA 的冷水 (0.7°C) 与最大的独角鲸种群有关 (>40000 头)。这些结果支持了海洋变暖将限制独角鲸栖息地范围的假设，进一步表明由于海洋变暖，来自中东和东南格陵兰的独角鲸可能面临放弃其传统栖息地的压力，因此要么向北迁徙更远，要么在当地灭绝。
