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We present centennial‐scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin. These novel stylasterids (Errinaspp.) were collected from the western Ross Sea shelf (500 m) and slope (1,700 m), as well as the eastern Wilkes Land shelf (670 m). We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral. We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change. We discuss a variety of possible drivers for this 14C reversal and conclude that it is most likely an encroachment of 14C‐depeleted Circumpolar Deep Water (CDW). This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; which has implications for global sea level, deep‐water formation, and carbon sequestration in the Southern Ocean. Thus, understanding the past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future. We estimate large‐scale encroachment of CDW onto the shelf likely commencing after 1830 CE (±120 year). We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint. This study not only demonstrates the utility of a novel coral taxon but also presents the paleoceanographic community with a testable hypothesis concerning a recent, widespread CDW intrusion. The Southern Ocean surrounds the continent of Antarctica and is made up of some of the world's oldest water. Waters from around the globe flow into the Southern Ocean where they can mix and flow back out to recirculate around the world. One such old water mass is Circumpolar Deep Water, or CDW, and it is made from parts of warm Atlantic waters and cool polar waters. Some Atlantic heat is retained in CDW and gives it a characteristic temperature of 1 °C, which is warm enough to melt ice around Antarctica. CDW is generally deeper than other waters and does not routinely interact with ice around Antarctica. Recently, CDW has been making its way up under ice shelves (the floating extension of land‐based ice) in Antarctica and melting significant amounts of ice. When the ice shelves melt, the support that they provide the grounded ice behind them is compromised, and large amounts of ice on land can flow faster out to sea. This has the potential to greatly increase global sea level, impacting the increasingly dense coastal communities around the world. Because CDW is also much older than other water masses in the Southern Ocean, it has a very distinct, old radiocarbon age. In this study, we employ deep sea stylasterid corals as archives of past ocean variability. As the corals grow, they incorporate chemical signals into their skeletons that reflect the chemical signals of the water they are living in, including radiocarbon. We analyze corals from two locations on the Antarctic continental shelf, located seaward of nearby ice shelves. These sites are 1,300 km (800 miles) apart in different settings at the western Ross Sea and eastern Wilkes Land margins. We expected that if the stylasterids were growing and there was no water mass change, the radiocarbon records should be older at the bottom of the specimen and younger at the top, similar to how we would expect a tree to grow. What we observe is an unexpected change in the younger portion of each coral; the ages become abruptly older. This suggests that at some point during the corals' lives, old CDW had moved in and forced them to record older ages. Further, the CDW intrusion was recorded by each coral, which suggests that this was a large‐scale event, happening over a wide range of the Antarctic margin. We convert the radiocarbon ages to calendar years and determine that the intrusion of CDW up onto the continental shelf roughly coincides with a time of stronger winds over the Southern Ocean as well as reduced bottom water formation in the midnineteenth century. Stronger westerly winds would force surface waters offshore, pulling CDW up onto the shelf to replace it. A reduced amount of bottom water being produced on the shelf (through ice freezing that rejects salty water that sinks to the bottom of the ocean); CDW could also be pulled up to fill a void. At this point we are unable to separate the true mechanism that caused CDW to flow up onto the continental shelf, but we are hopeful that with additional methods of age determination we can. What is more, we have evidence for an intrusion of CDW in a region of Antarctica that was previously unaffected. These findings could help us understand on what timescale CDW intrudes under ice shelves and help us better understand the possible impacts CDW‐induced melt could have in the near future. The understudied taxa of deep sea stylasterid corals reliably record oceanographic 14C changesChanges in local reservoir ages are evident at western Ross Sea and eastern Wilkes LandCorals record recent, persistent intrusion of Circumpolar Deep Water over a large expanse of the Antarctic margin

The characterisation of benthic habitats based on their abiotic (physical and chemical) attributes remains poorly defined in the marine environment, but is becoming increasingly central in the development of marine management plans in Australia and elsewhere in the world. The current study tested this link between physical and biological datasets for the southern Gulf of Carpentaria, Australia. The results presented were based on a range of physical factors, including the sediment composition (grain size and carbonate content), sediment mobility, water depth and organic carbon flux, and their relationship to the distribution and diversity of benthic macrofauna was tested. The results reveal the importance of process-based indices, such as sediment mobility, in addition to other environmental factors in defining the distribution of the benthic macrofauna. The distribution of the benthic macrofauna changes gradationally across the south-eastern Gulf, associated with changes in the per cent mud and gravel, the seabed exposure and the water depth. Patterns of diversity also reveal the importance of physical processes such as sediment mobility in defining benthic habitats. The species?environment relationships observed at the small scale of the current study are consistent with broader associations observed for other organisms within the Gulf.