Antarctica’s ecological isolation will be broken by storm-driven dispersal and warming

Abstract

Antarctica has long been considered biologically isolated1. Global warming will make parts of Antarctica more habitable for invasive taxa, yet presumed barriers to dispersal—especially the Southern Ocean’s strong, circumpolar winds, ocean currents and fronts—have been thought to protect the region from non-anthropogenic colonizations from the north1,2. We combine molecular and oceanographic tools to directly test for biological dispersal across the Southern Ocean. Genomic analyses reveal that rafting keystone kelps recently travelled >20,000 km and crossed several ocean-front ‘barriers’ to reach Antarctica from mid-latitude source populations. High-resolution ocean circulation models, incorporating both mesoscale eddies and wave-driven Stokes drift, indicate that such Antarctic incursions are remarkably frequent and rapid. Our results demonstrate that storm-forced surface waves and ocean eddies can dramatically enhance oceanographic connectivity for drift particles in surface layers, and show that Antarctica is not biologically isolated. We infer that Antarctica’s long-standing ecological differences have been the result of environmental extremes that have precluded the establishment of temperate-adapted taxa, but that such taxa nonetheless frequently disperse to the region. Global warming thus has the potential to allow the establishment of diverse new species—including keystone kelps that would drastically alter ecosystem dynamics—even without anthropogenic introductions.

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Fig. 1: Genomic analyses reveal that mid-latitude (Kerguelen, South Georgia) kelp dispersed thousands of kilometres to reach the Antarctic coast.
Fig. 2: Simulated drift particle trajectories from South Georgia.

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Acknowledgements

We thank J. Lee and F. le Bouard for assistance with at-sea observations, and the Antarctic Circumpolar Expedition and Swiss Polar Institute for facilitating the surveys. We thank A. McGaughran and W. Blanchard for analytical advice. Kelp samples used in analyses included some specimens collected by others—see acknowledgments in ref. 31. The oceanographic modelling was undertaken on the National Computational Infrastructure in Canberra, Australia, which is supported by the Australian Commonwealth Government. The research was funded by Australian Research Council grants to C.I.F. (DE140101715 and FT170100281) and A.K.M. (DE170100184), and Fondap-IDEAL grant 15150003 from CONICYT-Chile to E.C.M. and N.V.

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Contributions

C.I.F. and J.M.W. conceived the research. A.K.M., E.v.S. and A.M.H. conducted all oceanographic modelling. P.G.R. conducted the at-sea kelp surveys. E.C.M. and N.V. discovered and identified the drift samples from beaches in Antarctica. C.I.F. sourced (and in most cases, collected) the kelp samples used in the genomic analyses, and directed the genomic laboratory work carried out by A.P. C.J. contributed bioinformatics expertise and ran the genomic analyses. C.I.F. wrote the first draft of the paper. All authors contributed to editing the manuscript.

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Correspondence to Ceridwen I. Fraser.

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Supplementary information

41558_2018_209_MOESM3_ESM.mov

Example trajectories of 140 surface-bound Lagrangian particles released from South Georgia that did (orange trails) and did not (blue trails) reach the Antarctic shelf. The particles are advected by a combination of ocean currents and Stokes drift. Ocean current speed is indicated by colours. The tail on each particle shows its path over the last 50 days

Supplementary Information Description: Supplementary Figures 1–7, Supplementary Table 1

Supplementary Figures 1–7, Supplementary Table 1

Supplementary Table 2

Records of at-sea Durvillaea antarctica observations during the ACE voyage (2016-2017)

Supplementary Movie 1

Example trajectories of 140 surface-bound Lagrangian particles released from South Georgia that did (orange trails) and did not (blue trails) reach the Antarctic shelf. The particles are advected by a combination of ocean currents and Stokes drift. Ocean current speed is indicated by colours. The tail on each particle shows its path over the last 50 days

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Fraser, C.I., Morrison, A.K., Hogg, A.M. et al. Antarctica’s ecological isolation will be broken by storm-driven dispersal and warming. Nature Clim Change 8, 704–708 (2018). https://doi.org/10.1038/s41558-018-0209-7

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