The Cape Darnley region in East Antarctica has been an area of scientific interest for a variety of disciplines over the last three decades. The recent acquisition of several high-resolution bathymetry datasets enabled the compilation of a detailed regional bathymetry grid. We present a high-resolution bathymetric compilation of the Cape Darnley region in East Antarctica, including areas of the Mac.Robertson Land shelf, slope and adjacent deep sea. A variety of data, single-beam and multibeam swath bathymetry and digitized depths from nautical charts were sourced from numerous institutions. The 100 m-resolution gridded bathymetric dataset improves previous bathymetric representations of the region and enables visualization of the seafloor morphology in unprecedented detail. The bathymetry grid has been constructed using a layered hierarchy approach based on the source of each dataset. This data compilation forms important baseline information for a range of scientific applications and end users including oceanographers, glacial modellers, biologists and geologists. The compilation will aid numerical modelling of ocean circulation, reconstruction of palaeo-ice streams and refinement of ice-sheet models.

The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

A physical oceanographic, geophysical and marine geological survey of Edward VIII Gulf, Kemp Coast, collected data from conductivity–temperature–depth casts, multi-beam bathymetric swath mapping and 3.5 kHz sub-bottom surveying. Modified circumpolar deep water (mCDW) is observed in Edward VIII Gulf, as well as notable bathymetric features including mega-scale glacial lineations and a 1750 m-deep trough. Sedimentological, geochemical, rock-magnetic and micropalaeontological analysis of two kasten cores document regional palaeoclimate and palaeo-oceanographic conditions over the past 8000 years, with a warm period occurring from c. 8 to 4 ka and a shift to cooler conditions beginning at c. 4 ka and persisting until at least 0.9 ka. Sediment packages > 40 m thick within deep troughs in Edward VIII Gulf present potential targets for higher-resolution Holocene and deglacial climate studies. Despite the presence of mCDW on the shelf, inland bed topography consisting of highland terrain suggests the likelihood of relative stability of this sector of the East Antarctic Ice Sheet.

Radiocarbon accelerator mass spectrometric (AMS) dates on the acid-insoluble fraction from 38 core tops from the western Ross Sea, Antarctica, are used to address these questions: (1) What are the apparent ages of sediments at or close to the present sediment/water interface? (2) Is there a statistically significant pattern to the spatial distribution of core top ages? and (3) Is there a “correction factor” that can be applied to these age determinations to obtain the best possible Holocene (downcore) chronologies? Ages of core top sediments range from 2000 to 21,000 14C yr B.P. Some “old” core top dates are from piston cores and probably represent the loss of sediment during the coring process, but some core top samples >6000 14C yr B.P. may represent little or no Holocene deposition. Four possible sources of variability in dates ≤6000 14C yr B.P. (n = 28) are associated with (1) different sample preparation methods, (2) different sediment recovery systems, (3) different geographic regions, and (4) within-sample lateral age variability. Statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability; there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western Ross Sea and sites east of Ross Bank in south-central Ross Sea. The systematic variability in surface age between areas may be attributed to: (a) variable sediment accumulation rates (SAR) (surface age is inversely related to SAR), (b) differences in the percentage of reworked (dead) carbon between each area, and/or (c) differences in the CO2 exchange between the ocean and the atmosphere.

This study presents the first analysis of benthic megafauna and habitats from the Sabrina Coast shelf, encompassing a proposed Marine Protected Area. Sea bed imagery indicated an abundant benthic fauna compared to other parts of the Antarctic shelf, dominated by brittle stars, polychaete tubeworms, and a range of other sessile and mobile taxa. The distribution of taxa was related (ρ=0.592, P<0.001) to variations in water depth, latitude, substrate type and phytodetritus. High phytodetritus cover was associated with muddy/sandy sediments and abundant holothurians and amphipods, while harder substrates hosted abundant brachiopods, hard bryozoans, polychaete tubeworms, massive and encrusting sponges, and sea whips. Brittle stars, irregular urchins and anemones were ubiquitous. Variations in substrate largely reflected the distribution of dropstones, creating fine-scale habitat heterogeneity. Several taxa were found only on hard substrates, and their broad regional distribution indicated that the density of dropstones was sufficient for most sessile invertebrates to disperse across the region. The hexactinellid sponge Anoxycalyx joubini and branching hydrocorals exhibited a more restricted distribution, probably related to water depth and limited dispersal capability, respectively. Dropstones were associated with significant increases in taxa diversity, abundance and biological cover, enhancing the overall diversity and biomass of this ecosystem.

Fifty four surface sediment samples from the western and central Ross Sea were examined to determine relationships between modern oceanographic conditions and surface sediment diatom assemblages. A centered R mode principal components analysis demonstrates four geographically distinct assemblages. The assemblage just north of the Ross Ice Shelf in the central Ross Sea is most closely associated with Stephanopyxis spp. (a heavily silicified diatom abundant during the Pliocene), and may result from a combination of winnowing/reworking, and modern flux of primarily non-siliceous algae. The algal assemblage in the western part of the central Ross Sea is most closely associated with Thalassiosira gracilis (an open water diatom), and reflects early seasonal pack ice break up during the late spring inception of the Ross Sea polynya. The algal assemblage north of Drygalski Ice Tongue, in the western Ross Sea, is most closely associated with Fragilariopsis curta (a diatom common in stratified ice edge zones), suggesting that water column seeding by species melting out of coastal sea ice is important in this area. The assemblage south of Drygalski Ice Tongue is most closely associated with resting spores of Thalassiosira antarctica (a diatom associated with coastal waters). Although the habitat of T. antarctica requires future research, we speculate that sea ice conditions unique to area B support an autumnal T. antarctica bloom.

Fossil diatom-bearing marine sediment cores recovered from Prydz Channel, Prydz Bay, record episodes of glacial advance and retreat in the bay. Diatom frustules are abundant, well preserved, and the species composition is diverse in two biogenic sediment units composed of siliceous diatom ooze (SMO-1 and SMO-2). Between SMO-1 and SMO-2 a terrigenous unit (T) is present, composed of muddy diamicton and sandy silty clay, which contains poorly preserved rare diatoms. The SMO units are interpreted to represent an open marine setting with seasonal sea ice cover; the T unit is interpreted to represent glacial ice expansion from the Amery Ice Shelf over the site. Based on an age model developed previously for other cores from Prydz Channel with analogous stratigraphies, we interpret our record to be late Quaternary through Holocene in age. The T unit records the Last Glacial Maximum (LGM) in Prydz Bay; the SMO-1 and SMO-2 units record interstadial episodes that are post- and pre-LGM respectively. Extinct diatom taxa in the T and SMO-2 units indicate reworked sediment sourced from two different-aged deposits. Our results provide both a new interpretation of late Quaternary deposition in Prydz Channel and support for previous studies in this region.

A world-wide study of the Oidium species causing economic damage on tomato has identified two taxa using classical morphological, scanning electron microscope (SEM) and molecular phylogenetic analyses. The material consisted of a total of 25 tomato powdery mildew isolates and 29 herbarium specimens coming from all continents where tomatoes are grown. A taxon with non-catenate conidia widespread in Europe, Africa, North and South America and Asia was identified as an O. subgen. Pseudoidium species (teleomorph: Erysiphe sect. Erysiphe). Formerly mistaken for O. lycopersicum (or O. lycopersici), it is now recognised as a distinct species, O. neolycopersici sp. nov. A phylogenetic analysis of the internal transcribed spacer (ITS) sequences of the ribosomal DNA (rDNA) indicated that O. neolycopersici is closely related to Erysiphe macleayae, E. aquilegiae and other Pseudoidium species. Only a taxon with catenate conidia was found on Australian specimens. This was identified as a species of O. subgen. Reticuloidium (teleomorph: Golovinomyces sp.). Phylogenetic analysis of the rDNA ITS sequences showed that this species is closely related to O. longipes infecting eggplant. Because it is most likely to be the same species as the original O. lycopersicum, which was actually first described in Australia, this is here neotypified as O. lycopersici.