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Highly diverse, poorly studied and uniquely threatened by climate change: an assessment of marine biodiversity on South Georgia's continental shelf.

Hogg OT, Barnes DK, Griffiths HJ - PLoS ONE (2011)

Bottom Line: We attempt to quantify how significant the polar archipelago of South Georgia is as a source of regional and global marine biodiversity.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.

View Article: PubMed Central - PubMed

Affiliation: British Antarctic Survey, Natural Environmental Research Council, Cambridge, United Kingdom. olgg@bas.ac.uk

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.

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Species richness of eight major phyla on the South Georgia shelf.Dark grey bars show actual number of species recorded for each taxa; Light grey bars represent an estimated total species richness extrapolated using Chao 1(left hand column for each phyla) and Jacknife 2 (right hand column).
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pone-0019795-g010: Species richness of eight major phyla on the South Georgia shelf.Dark grey bars show actual number of species recorded for each taxa; Light grey bars represent an estimated total species richness extrapolated using Chao 1(left hand column for each phyla) and Jacknife 2 (right hand column).

Mentions: Rarefaction curves show the rate at which new species were accumulated with increasing sampling effort (Figure 9). In no phylum did such curves reach asymptote. The two most intensively recorded phyla, the chordates and crustaceans showed differentials of 0.02 and 0.05 new species per new sample site respectively. Echinoderms (0.38), sponges (0.35), and particularly bryozoans (0.67) retained high rates of species accumulation and as such represent the three phyla for which current biodiversity estimates are poorest. These trends were supported by Chao 1 and Jacknife 2 species richness estimators which respectively reported only 44% and 50% of probable bryozoans present at South Georgia as currently represented in our sampling. Comparatively, using the same estimators averaged across all eight major phyla 72.8% (σ = 13.3) and 65.8% (σ = 7.2) of estimated species richness was represented by our sampling). Extrapolations based on these eight phyla (representative of 82.6% of total species) place total species richness at 1,627 (Chao 1) and 1,760 (Jacknife 2). Relative variance in biodiversity between the major phyla with the exception of bryozoans remained relatively constant with rank order species richness remaining unchanged (Figure 10). Extrapolations based on the inclusion of all 22 recorded phyla at South Georgia however, produced much higher species estimates and a greater degree of variance between estimators with Chao 1 predicting 1,979 species compared to 2,366 estimated by Jacknife 2. Such large variances are unsurprising with the inclusion of under sampled minor phyla such as brachiopods (table 1) and phyla with geographically constricted sampling, as with nematodes.


Highly diverse, poorly studied and uniquely threatened by climate change: an assessment of marine biodiversity on South Georgia's continental shelf.

Hogg OT, Barnes DK, Griffiths HJ - PLoS ONE (2011)

Species richness of eight major phyla on the South Georgia shelf.Dark grey bars show actual number of species recorded for each taxa; Light grey bars represent an estimated total species richness extrapolated using Chao 1(left hand column for each phyla) and Jacknife 2 (right hand column).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102052&req=5

pone-0019795-g010: Species richness of eight major phyla on the South Georgia shelf.Dark grey bars show actual number of species recorded for each taxa; Light grey bars represent an estimated total species richness extrapolated using Chao 1(left hand column for each phyla) and Jacknife 2 (right hand column).
Mentions: Rarefaction curves show the rate at which new species were accumulated with increasing sampling effort (Figure 9). In no phylum did such curves reach asymptote. The two most intensively recorded phyla, the chordates and crustaceans showed differentials of 0.02 and 0.05 new species per new sample site respectively. Echinoderms (0.38), sponges (0.35), and particularly bryozoans (0.67) retained high rates of species accumulation and as such represent the three phyla for which current biodiversity estimates are poorest. These trends were supported by Chao 1 and Jacknife 2 species richness estimators which respectively reported only 44% and 50% of probable bryozoans present at South Georgia as currently represented in our sampling. Comparatively, using the same estimators averaged across all eight major phyla 72.8% (σ = 13.3) and 65.8% (σ = 7.2) of estimated species richness was represented by our sampling). Extrapolations based on these eight phyla (representative of 82.6% of total species) place total species richness at 1,627 (Chao 1) and 1,760 (Jacknife 2). Relative variance in biodiversity between the major phyla with the exception of bryozoans remained relatively constant with rank order species richness remaining unchanged (Figure 10). Extrapolations based on the inclusion of all 22 recorded phyla at South Georgia however, produced much higher species estimates and a greater degree of variance between estimators with Chao 1 predicting 1,979 species compared to 2,366 estimated by Jacknife 2. Such large variances are unsurprising with the inclusion of under sampled minor phyla such as brachiopods (table 1) and phyla with geographically constricted sampling, as with nematodes.

Bottom Line: We attempt to quantify how significant the polar archipelago of South Georgia is as a source of regional and global marine biodiversity.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.

View Article: PubMed Central - PubMed

Affiliation: British Antarctic Survey, Natural Environmental Research Council, Cambridge, United Kingdom. olgg@bas.ac.uk

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.

Show MeSH