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Australian Government Geoscience Australia

This study explores the application of geomorphic mapping and physical data to understand the bioregionalisation of Prydz Bay. Using various data sources, the study identifies key geomorphic features and their influence on seabed community structure. Results indicate the significance of phytodetritus flux and substrate types in shaping ecosystems in the area.

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Australian Government Geoscience Australia

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  1. Australian Government Geoscience Australia Applications of geomorphic mapping and physical data to bioregionalisation Alix Post & Phil O’Brien Geoscience Australia www.ga.gov.au

  2. Sessile suspension feeder community Infauna and mobile deposit feeder community Primary controls – Phytodetritus flux and sea bed “hardness” Macro-zoobenthos core communitiesGutt (2007)

  3. N Creating geomorphic map Input data • GEBCO contours • ETOPO2 satellite bathymetry grid • Seismic lines Output • Polygons hand digitised in ArcGIS • 28 categories of geomorphic features recognised

  4. Prydz Bay

  5. Cross shelf valleys: Shelf depression <500 m connected to shelf edge. May be current swept. Shelf bank: Typically 100-200 m, extending to 500 m. Ice scoured. Prydz Bay Shelf depression: < 550 m with closed contours. Typically muddy, biogenic sediments.

  6. Lower slope: Extends to lower limit of canyons. Comprises alt. canyons and ridges. Trough mouth fan: Sediment apron on upper slope. Prydz Bay Upper slope: Mapped from max gradient to lower gradient at ~2500 m. Highly gullied and current swept.

  7. Prydz Bay – Sediments & geomorphology Phytodetritus-rich ooze distribution controlled by geomorphology

  8. Seamount on seismic line Height above seabed > 1000 m

  9. Marginal ridge – Outer Adélie Rift Block 10 km S N D1601 Granite, gneiss, diorite, pelite 5 6 7

  10. George V-Terra Adélie margin – Geomorphic Units

  11. Biogeomorphic units George V shelf Beaman & Harris, (2005) Data: Multibeam Single beam Grab samples Cores Photos CTDs

  12. Mertz Drift Presti et al., Quaternary Science Reviews, 2005

  13. PCA of taxa with correlation to substrate Coarse substrate Rocky substrate Deep/ flat Relief Scours Muddy Sponges & bryozoa Sponges & solitary tunicates Bryozoa, sponges, colonial tunicates Shrimp, infaunal holothurians Bryozoa, sponges, soft corals Spearman rank correlation = 0.71 Post et al., DSR II in press

  14. Hydrocorals and canyon heads, George V continental slope (Post et al., Ant. Sci, 2010)

  15. Shelf geomorphic units approximate Community-level habitats Public bathymetry data sets useful for bioregionalsiation on the scale of around 1: 1 million Should have value for the slope, rise and deep ocean Conclusions

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