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

• Published in: Science of The Total Environment
• Main Authors: Frinault, B.A.V., Barnes, D.K.A., Biskaborn, B.K., Gromig, R., Hillenbrand, C.-D., Klages, J.P., Koglin, N., Kuhn, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: Antarc*; Antarctic; Ice Shelf; Ice Shelves
• Online Access: http://nora.nerc.ac.uk/id/eprint/535656/; https://nora.nerc.ac.uk/id/eprint/535656/1/1-s2.0-S0048969723047824-main.pdf; https://www.sciencedirect.com/science/article/pii/S0048969723047824

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 ...