Submarine sedimentary bedforms and benthos surrounding the Heard and McDonald Islands World Heritage site
2020
We present highlights of the first multibeam and bottom sampling survey surrounding the UNESCO World
Heritage listed Heard and McDonald Islands (HIMI), conducted in the HIMI Marine Reserve InnerMarine
Zone. These insular shelf data reveal that persistent eastward flowing currents and retreating glaciers drive
patterns of sediment distribution. Sedimentary bedform directionality, corroborated by drifter data, suggest
that the prevailing energy in this region dominates from west to east, and is deflected in an anticlockwise
direction around Heard Island, causing sediment deposition to be concentrated on the eastern (downcurrent)
side of the islands. Sediment bedform morphology likely mirrors the eastward flowing Antarctic
Circumpolar Current and oscillating east!west tidal currents. Thick sediment accumulations north of
Heard Island may be related to deglaciation since the Last Glacial Maximum.
Sample sites on the northern down-current side of Heard Islands and on the western up-current
side of the McDonald Islands contain a diverse range of taxonomic groups compared to all other
sample sites. Benthic specimens obtained in rock dredges and sediment grabs show a range of
invertebrate species that are likely endemic to the HIMI region.
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