Centre for Planetary Health and Food Security, Southern Ocean Persistent Organic Pollutants Program, Griffith University, 4111 Nathan, QLD, Australia; Alfred-Wegener-Institute Helmholtz-Centre for Polar and Marine Research, Bremerhaven, Germany; Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg (HIFMB), Ammerländer Heerstrasse 231, 26129 Oldenburg, Germany.
Institute for Marine and Antarctic Studies, University of Tasmania, 7004 Hobart, TAS, Australia.
Sci Total Environ. 2024 Jun 25;931:172939. doi: 10.1016/j.scitotenv.2024.172939. Epub 2024 May 1.
Southern hemisphere humpback whale (Megaptera novaeangliae, SHHW) breeding populations follow a high-fidelity Antarctic krill (Euphausia superba) diet while feeding in distinct sectors of the Southern Ocean. Their capital breeding life history requires predictable ecosystem productivity to fuel migration and migration-related behaviours. It is therefore postulated that populations feeding in areas subject to the strongest climate change impacts are more likely to show the first signs of a departure from a high-fidelity krill diet. We tested this hypothesis by investigating blubber fatty acid profiles and skin stable isotopes obtained from five SHHW populations in 2019, and comparing them to Antarctic krill stable isotopes sampled in three SHHW feeding areas in the Southern Ocean in 2019. Fatty acid profiles and δC and δN varied significantly among all five populations, however, calculated trophic positions did not (2.7 to 3.1). Similarly, fatty acid ratios, 16:1ω7c/16:0 and 20:5ω3/22:6ω3 were above 1, showing that whales from all five populations are secondary heterotrophs following an omnivorous diet with a diatom-origin. Thus, evidence for a potential departure from a high-fidelity Antarctic krill diet was not seen in any population. δC of all populations were similar to δC of krill sampled in productive upwelling areas or the marginal sea-ice zone. Consistency in trophic position and diet origin but significant fatty acid and stable isotope differences demonstrate that the observed variability arises at lower trophic levels. Our results indicate that, at present, there is no evidence of a divergence from a high-fidelity krill diet. Nevertheless, the characteristic isotopic signal of whales feeding in productive upwelling areas, or in the marginal sea-ice zone, implies that future cryosphere reductions could impact their feeding ecology.
南半球露脊鲸（Megaptera novaeangliae，SHHW）繁殖群体在南大洋的不同区域以高度保真的南极磷虾（Euphausia superba）为食。它们的主要繁殖生命周期需要可预测的生态系统生产力来为迁徙和与迁徙相关的行为提供燃料。因此，人们推测，在受气候变化影响最大的地区觅食的种群更有可能首先表现出偏离高保真磷虾饮食的迹象。我们通过调查 2019 年五个南半球露脊鲸种群的鲸脂脂肪酸谱和皮肤稳定同位素，并将其与 2019 年在南大洋五个南半球露脊鲸觅食区采集的南极磷虾稳定同位素进行比较，检验了这一假设。脂肪酸谱和 δC 和 δN 在所有五个种群中均有显著差异，但计算的营养位（2.7 至 3.1）没有差异。同样，脂肪酸比 16:1ω7c/16:0 和 20:5ω3/22:6ω3 均高于 1，表明所有五个种群的鲸鱼均为以硅藻为食的二级异养动物。因此，没有任何一个种群有证据表明可能会偏离高保真的南极磷虾饮食。所有种群的 δC 均与在生产力上升区或边缘海冰区采集的磷虾的 δC 相似。营养位和饮食起源的一致性以及显著的脂肪酸和稳定同位素差异表明，观察到的变异性出现在较低的营养水平。我们的研究结果表明，目前没有证据表明南半球露脊鲸会偏离高保真的磷虾饮食。然而，在生产力上升区或边缘海冰区觅食的鲸鱼的特征同位素信号表明，未来的冰冻圈减少可能会影响它们的觅食生态。
