Spatial competition in a global disturbance minimum; the seabed under an Antarctic ice shelf

Bétina A V Frinault; David K A Barnes; Boris K Biskaborn; Raphael Gromig; Claus-Dieter Hillenbrand; Johann P Klages; Nikola Koglin; Gerhard Kuhn

doi:10.1016/j.scitotenv.2023.166157

Spatial competition in a global disturbance minimum; the seabed under an Antarctic ice shelf

Sci Total Environ. 2023 Dec 10:903:166157. doi: 10.1016/j.scitotenv.2023.166157. Epub 2023 Aug 11.

Authors

Bétina A V Frinault¹, David K A Barnes², Boris K Biskaborn³, Raphael Gromig⁴, Claus-Dieter Hillenbrand², Johann P Klages⁴, Nikola Koglin⁵, Gerhard Kuhn⁴

Affiliations

¹ School of Geography and the Environment, Oxford University Centre for the Environment, University of Oxford, Oxford, UK. Electronic address: betina.frinault@ouce.ox.ac.uk.
² British Antarctic Survey, Natural Environment Research Council, Cambridge, UK.
³ Alfred-Wegeneer-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Potsdam, Germany.
⁴ Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany.
⁵ Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany.

PMID: 37572912
DOI: 10.1016/j.scitotenv.2023.166157

Abstract

The marine habitat beneath Antarctica's ice shelves spans ∼1.6 million km², and life in this vast and extreme environment is among Earth's least accessible, least disturbed and least known, yet likely to be impacted by climate-forced warming and environmental change. Although competition among biota is a fundamental structuring force of ecological communities, hence ecosystem functions and services, nothing was known of competition for resources under ice shelves, until this study. Boreholes drilled through a ∼ 200 m thick ice shelf enabled collections of novel sub-ice-shelf seabed sediment which contained fragments of biogenic substrata rich in encrusting (lithophilic) macrobenthos, principally bryozoans - a globally-ubiquitous phylum sensitive to environmental change. Analysis of sub-glacial biogenic substrata, by stereo microscopy, provided first evidence of spatial contest competition, enabling generation of a new range of competition measures for the sub-ice-shelf benthic space. Measures were compared with those of global open-water datasets traversing polar, temperate and tropical latitudes (and encompassing both hemispheres). Spatial competition in sub-ice-shelf samples was found to be higher in intensity and severity than all other global means. The likelihood of sub-ice-shelf competition being intraspecific was three times lower than for open-sea polar continental shelf areas, and competition complexity, in terms of the number of different types of competitor pairings, was two-fold higher. As posited for an enduring disturbance minimum, a specific bryozoan clade was especially competitively dominant in sub-ice-shelf samples compared with both contemporary and fossil assemblage records. Overall, spatial competition under an Antarctic ice shelf, as characterised by bryozoan interactions, was strikingly different from that of open-sea polar continental shelf sites, and more closely resembled tropical and temperate latitudes. This study represents the first analysis of sub-ice-shelf macrobenthic spatial competition and provides a new ecological baseline for exploring, monitoring and comparing ecosystem response to environmental change in a warming world.

Keywords: Boreholes through ice shelves; Bryozoa; Global climate change; Macrobenthos interactions; Stereo microscopy; Weddell Sea.