在捕鲸时代和气候快速变化时期，南大洋捕食者环极地区觅食范围的长期稳定性
Long-term stability in the circumpolar foraging range of a Southern Ocean predator between the eras of whaling and rapid climate change
作者：Solène Derville, Leigh G. Torres, Seth D. Newsome, Christopher J. Somes, Luciano O. Valenzuela, Hannah B. Vander Zanden, C. Scott Baker, Martine Bérubé, Geraldine Busquets-Vass, Kris Carlyon, Simon J. Childerhouse, Rochelle Constantine, Glenn Dunshea, Paulo A. C. Flores, Simon D. Goldsworthy, Brittany Graham, Karina Groch, Darren R. Gröcke, Robert Harcourt, Mark A. Hindell, Pavel Hulva, Jennifer A. Jackson, Amy S. Kennedy, David Lundquist, Alice I. Mackay, Petra Neveceralova, Larissa Oliveira, Paulo H. Ott, Per J. Palsbøll, Nathalie J. Patenaude, Victoria Rowntree, Mariano Sironi, Els Vermeuelen, Mandy Watson, Alexandre N. Zerbini, and Emma L. Carroll
期刊：PNAS
Assessing environmental changes in Southern Ocean ecosystems is difficult due to its remoteness and data sparsity. Monitoring marine predators that respond rapidly to environmental variation may enable us to track anthropogenic effects on ecosystems. Yet, many long-term datasets of marine predators are incomplete because they are spatially constrained and/or track ecosystems already modified by industrial fishing and whaling in the latter half of the 20th century. Here, we assess the contemporary offshore distribution of a wide-ranging marine predator, the southern right whale (SRW, Eubalaena australis), that forages on copepods and krill from ~30°S to the Antarctic ice edge (>60°S). We analyzed carbon and nitrogen isotope values of 1,002 skin samples from six genetically distinct SRW populations using a customized assignment approach that accounts for temporal and spatial variation in the Southern Ocean phytoplankton isoscape. Over the past three decades, SRWs increased their use of mid-latitude foraging grounds in the south Atlantic and southwest (SW) Indian oceans in the late austral summer and autumn and slightly increased their use of high-latitude (>60°S) foraging grounds in the SW Pacific, coincident with observed changes in prey distribution and abundance on a circumpolar scale. Comparing foraging assignments with whaling records since the 18th century showed remarkable stability in use of mid-latitude foraging areas. We attribute this consistency across four centuries to the physical stability of ocean fronts and resulting productivity in mid-latitude ecosystems of the Southern Ocean compared with polar regions that may be more influenced by recent climate change.
Fig. 1. Distribution of sampling location and stable isotope values for SRW skin samples. (A) Biplot of skin δ13C and δ15N values for each wintering ground. The dark gray rectangle delineates the subset of Argentinian samples with high δ15N values. (B) Map of sample collection locations by wintering ground; note Australia wintering grounds are divided into SW and SE. (C) Mean δ13C and δ15N values summarized by wintering grounds; error bars denote SD.
南大洋地处偏远，再加上相关数据稀少，因此评估其生态系统的环境变化十分困难。监测那些对环境变化反应迅速的海洋捕食者能让我们追踪记录人类对生态系统的影响。然而因为受到空间限制，以及或者是因为生态系统追踪已经被20世纪后半叶的工业捕鱼和捕鲸所改变，关于许多海洋捕食者的长期数据集不完整。本文中我们评估了一种分布广泛的海洋捕食者—南露脊鲸（SRW，Eubalaena australis）的当代离岸分布，南露脊鲸在南纬30度到南极冰缘（>60度）之间捕食桡足类和磷虾。我们使用一种定制的分配方法分析了在遗传上不同的六个南露脊鲸种群的1002个皮肤样本的碳和氮同位素值，该方法同时兼顾考虑了南大洋浮游植物等值线的时间和空间变化。在过去的三十年中，每到南半球夏末和秋天的时候，南露脊鲸在南大西洋和西南印度洋的中纬度地区觅食地的使用量有所增加，在西南太平洋高纬度（>60°S）地区觅食地的使用量略有增加，这与在极地范围内观察到的猎物分布和丰度变化是一致的。将觅食分布与18世纪以来的捕鲸记录相比较发现中纬度觅食区使用量具有显著稳定性。我们将这种跨越四个世纪的一致性归因于海洋锋面的物理稳定性和由此给南大洋中纬度地区生态系统提供的生产力，而极地地区则可能是因为近年来受气候变化的影响更大。
