Abstract
We attempt to quantify how significant the polar archipelago of South Georgia is as a source of regional and global marine biodiversity. We evaluate numbers of rare, endemic and range-edge species and how the faunal structure of South Georgia may respond to some of the fastest warming waters on the planet.Biodiversity data was collated from a comprehensive review of reports, papers and databases, collectively representing over 125 years of polar exploration. Classification of each specimen was recorded to species level and fully geo-referenced by depth, latitude and longitude. This information was integrated with physical data layers (e.g. temperature, salinity and flow) providing a visualisation of South Georgia's biogeography across spatial, temporal and taxonomic scales, placing it in the wider context of the Southern Hemisphere.This study marks the first attempt to map the biogeography of an archipelago south of the Polar Front. Through it we identify the South Georgian shelf as the most speciose region of the Southern Ocean recorded to date. Marine biodiversity was recorded as rich across taxonomic levels with 17,732 records yielding 1,445 species from 436 families, 51 classes and 22 phyla. Most species recorded were rare, with 35% recorded only once and 86% recorded <10 times. Its marine fauna is marked by the cumulative dominance of endemic and range-edge species, potentially at their thermal tolerance limits. Consequently, our data suggests the ecological implications of environmental change to the South Georgian marine ecosystem could be severe. If sea temperatures continue to rise, we suggest that changes will include depth profile shifts of some fauna towards cooler Antarctic Winter Water (90–150 m), the loss of some range-edge species from regional waters, and the wholesale extinction at a global scale of some of South Georgia's endemic species.
Highlights
The archipelago of South Georgia represents one of the largest, most isolated land masses and continental shelf areas in the Southern Ocean
Biodiversity at South Georgia Geo-referenced biodiversity data for South Georgia held in open access databases offered a relatively poor representation of known marine life around the island
By contrast this study adopted a macro-ecological approach to recording island level biodiversity, and as such represents the first attempt to map the biogeography of an archipelago south of the Polar Front
Summary
The archipelago of South Georgia represents one of the largest, most isolated land masses and continental shelf areas in the Southern Ocean. The Polar Front (PF) passes approximately 300 km to the north (mean distance derived from [4]) with the South ACC current, which transports nutrients and organisms (e.g. krill) from the Antarctic Peninsula, to the south [5] The combination of this early separation from a continental land mass, a large shelf area, its high degree of geographic isolation and the proximity of nutrient rich currents represent important catalysts in the evolution of a biologically rich and distinct island, and identify South Georgia as a potentially important locality for biodiversity. In addition its waters support commercially important fisheries of Patagonian toothfish (Dissostichus eleginoides), mackerel icefish (Champsocephalus gunnari) and Antarctic krill (Euphausia superb) It may be the most northern continental shelf with no known non indigenous marine species. Model projections suggest that over the coming decades the South Georgia will experience increased stress from ocean wide acidification [12]
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