scholarly journals Regional differentiation and extensive hybridization between mitochondrial clades of the Southern Ocean giant sea spider Colossendeis megalonyx

2015 ◽  
Vol 2 (7) ◽  
pp. 140424 ◽  
Author(s):  
Lars Dietz ◽  
Claudia P. Arango ◽  
Jana S. Dömel ◽  
Kenneth M. Halanych ◽  
Avril M. Harder ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Cryptic Species ◽  
Global Climate ◽  
Regional Differentiation ◽  
Internal Transcribed Spacer Region ◽  
Mitochondrial Coi ◽  
Sea Spider ◽  
Distribution Ranges ◽  
Multiple Species ◽  
The Antarctic

Assessing the enormous diversity of Southern Ocean benthic species and their evolutionary histories is a central task in the era of global climate change. Based on mitochondrial markers, it was recently suggested that the circumpolar giant sea spider Colossendeis megalonyx comprises a complex of at least six cryptic species with mostly small and non-overlapping distribution ranges. Here, we expand the sampling to include over 500 mitochondrial COI sequences of specimens from around the Antarctic. Using multiple species delimitation approaches, the number of distinct mitochondrial OTUs increased from six to 15–20 with our larger dataset. In contrast to earlier studies, many of these clades show almost circumpolar distributions. Additionally, analysis of the nuclear internal transcribed spacer region for a subset of these specimens showed incongruence between nuclear and mitochondrial results. These mito-nuclear discordances suggest that several of the divergent mitochondrial lineages can hybridize and should not be interpreted as cryptic species. Our results suggest survival of C. megalonyx during Pleistocene glaciations in multiple refugia, some of them probably located on the Antarctic shelf, and emphasize the importance of multi-gene datasets to detect the presence of cryptic species, rather than their inference based on mitochondrial data alone.

Southern Ocean Response to Strengthening Winds in an Eddy-Permitting Global Climate Model

2010 ◽  
Vol 23 (19) ◽  
pp. 5332-5343 ◽  
Author(s):  
Paul Spence ◽  
John C. Fyfe ◽  
Alvaro Montenegro ◽  
Andrew J. Weaver
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Temperature Response ◽  
Near Surface ◽  
Ocean Response ◽  
Circumpolar Current ◽  
The Antarctic

Abstract A global climate model with horizontal resolutions in the ocean ranging from relatively coarse to eddy permitting is used to investigate the resolution dependence of the Southern Ocean response to poleward intensifying winds through the past and present centuries. The higher-resolution simulations show poleward migration of distinct ocean fronts associated with a more highly localized near-surface temperature response than in the lower-resolution simulations. The higher-resolution simulations also show increasing southward eddy heat transport, less high-latitude cooling, and greater sea ice loss than the lower-resolution simulations. For all resolutions, from relatively coarse to eddy permitting, there is poleward migration of the Antarctic Circumpolar Current in the Atlantic and the western half of the Indian basin. Finally, zonal transports associated with the Antarctic Circumpolar Current are shown to be sensitive to resolution, and this is discussed in the context of recent observed change.

Evaluation of the numerical wave model (WaveWatch III) for wave simulation in the Antarctic marginal ice zone

2020 ◽  
Author(s):  
Marzieh H. Derkani ◽  
Katrin Hessner ◽  
Stefan Zieger ◽  
Filippo Nelli ◽  
Alberto Alberello ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Southern Hemisphere ◽  
Global Climate ◽  
Wave Model ◽  
Open Ocean ◽  
Wavewatch Iii ◽  
Marginal Ice Zone ◽  
The Antarctic ◽  
The Impact

<p>The Southern Ocean is the birthplace of the fiercest waves on the Earth, which play a fundamental role in global climate by regulating momentum, heat and gas exchanges between the atmosphere and ocean. At high latitudes, waves interact with Antarctic sea ice, another crucial player of the Earth's climate system, modulating its expansion in the winter and its retreat in summer and hence affecting the global albedo. Despite the impact of waves on climate, global wave models are considerably biased in the Southern Hemisphere, due to the scarcity of observations in these remote waters. This is exacerbated in the marginal ice zone, the region of ice-covered water between the compact ice or land and the open ocean, where surface waves, upper ocean and atmosphere interact with sea ice but the dominant physics are still largely unknown. To improve our understanding of physical processes in Southern Ocean and model capabilities, the Antarctic Circumnavigation Expedition (ACE) sailed these waters from December 2016 to March 2017 to acquire wave data (among other climate variables) both in the open ocean and Antarctic marginal ice zone. Observations were gathered using a radar-based wave and surface current monitoring system (WaMoS-II) built on board of the research icebreaker Akademik Tryoshnikov. Here, we discuss how these observations underpin the set up, calibration and validation of the WaveWatch III wave model over a domain covering the entire Southern Hemisphere, therefore spanning from tropical waters to the edge of sea ice (open waters only). The calibrated model will then be used to carry out a thorough assessment of different sea ice modules, to evaluate accuracy of predictions in the marginal ice zone. Test cases of waves-in-ice recorded during the Antarctic Circumnavigation Expeditions will be discussed in details.</p>

scholarly journals Receding ice drove parallel expansions in Southern Ocean penguins

2019 ◽  
Vol 116 (52) ◽  
pp. 26690-26696 ◽  
Author(s):  
Theresa L. Cole ◽  
Ludovic Dutoit ◽  
Nicolas Dussex ◽  
Tom Hart ◽  
Alana Alexander ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Global Climate ◽  
Biological Effects ◽  
Ecosystem Change ◽  
Emperor Penguin ◽  
Ecological Change ◽  
Ice Conditions ◽  
Demographic Shifts ◽  
Multiple Species

Climate shifts are key drivers of ecosystem change. Despite the critical importance of Antarctica and the Southern Ocean for global climate, the extent of climate-driven ecological change in this region remains controversial. In particular, the biological effects of changing sea ice conditions are poorly understood. We hypothesize that rapid postglacial reductions in sea ice drove biological shifts across multiple widespread Southern Ocean species. We test for demographic shifts driven by climate events over recent millennia by analyzing population genomic datasets spanning 3 penguin genera (Eudyptes,Pygoscelis, andAptenodytes). Demographic analyses for multiple species (macaroni/royal, eastern rockhopper, Adélie, gentoo, king, and emperor) currently inhabiting southern coastlines affected by heavy sea ice conditions during the Last Glacial Maximum (LGM) yielded genetic signatures of near-simultaneous population expansions associated with postglacial warming. Populations of the ice-adapted emperor penguin are inferred to have expanded slightly earlier than those of species requiring ice-free terrain. These concerted high-latitude expansion events contrast with relatively stable or declining demographic histories inferred for 4 penguin species (northern rockhopper, western rockhopper, Fiordland crested, and Snares crested) that apparently persisted throughout the LGM in ice-free habitats. Limited genetic structure detected in all ice-affected species across the vast Southern Ocean may reflect both rapid postglacial colonization of subantarctic and Antarctic shores, in addition to recent genetic exchange among populations. Together, these analyses highlight dramatic, ecosystem-wide responses to past Southern Ocean climate change and suggest potential for further shifts as warming continues.

scholarly journals The rapid divergence of the Antarctic crinoid species Promachocrinus kerguelensis

2019 ◽  
Author(s):  
Yacine Ben Chehida ◽  
Marc Eléaume ◽  
Cyril Gallut ◽  
Guillaume Achaz
Keyword(s):  
Southern Ocean ◽  
Cryptic Species ◽  
Marine Invertebrates ◽  
Sampling Effort ◽  
Last Common Ancestor ◽  
International Polar Year ◽  
Climatic Oscillations ◽  
Rapid Divergence ◽  
Turn Over ◽  
The Antarctic

AbstractClimatic oscillations in Antarctica caused a succession of expansion and reduction of the ice sheets covering the continental shelf of the Southern Ocean. For marine invertebrates, these successions are suspected to have driven allopatric speciation, endemism and the prevalence of cryptic species, leading to the so-called Antarctic ‘biodiversity pump’ hypothesis. Here we took advantage of the recent sampling effort influenced by the International Polar Year (2007-8) to test for the validity of this hypothesis for 1,797 samples of two recognized crinoid species: Promachocrinus kerguelensis and Florometra mawsoni. Species delimitation analysis identified seven phylogroups. As previously suggested, Promachocrinus kerguelensis forms a complex of six cryptic species. Conversely, despite the morphological differences, our results show that Florometra mawsoni is a lineage nested within Promachocrinus kerguelensis. It suggests that Florometra mawsoni and Promachocrinus kerguelensis belong to the same complex of species. Furthermore, this study indicates that over time and space the different sectors of the Southern Ocean show a remarkable rapid turn-over in term of phylogroups composition and also of genetic variants within phylogroups. We argue that strong “apparent” genetic drift causes this rapid genetic turn-over. Finally, we dated the last common ancestor of all phylogroups at less than 1,000 years, raising doubts on the relevance of the Antarctic “biodiversity pump” for this complex of species. This work is a first step towards a better understanding of how life is diversifying in the Southern Ocean.

Human-Induced Change in the Antarctic Circumpolar Current

2005 ◽  
Vol 18 (15) ◽  
pp. 3068-3073 ◽  
Author(s):  
John C. Fyfe ◽  
Oleg A. Saenko
Keyword(s):  
Southern Ocean ◽  
Arctic Ocean ◽  
Antarctic Circumpolar Current ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Oceanic Response ◽  
Poleward Shift ◽  
Circumpolar Current ◽  
The Antarctic

Abstract Global climate models indicate that the poleward shift of the Antarctic Circumpolar Current observed over recent decades may have been significantly human induced. The poleward shift, along with a significant increase in the transport of water around Antarctica, is predicted to continue into the future. To appreciate the magnitude of the poleward shift it is noted that by century’s end the concomitant shrinking of the Southern Ocean is predicted to displace a volume of water close to that in the entire Arctic Ocean. A simple theory, balancing surface Ekman drift and ocean eddy mixing, explains these changes as the oceanic response to changing wind stress.

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