Biologically relevant macronutrients, nitrate + nitrite, silicate, phosphate and ammonia, were measured at all sites throughout the study. Nitrate + nitrite values (NOx) at the surface showed clear seasonal trends, peaking over winter and drawing down to near zero in summer and autumn. Phosphate concentrations also reached a peak in winter, which was associated with Southern Ocean influence. Median ammonium concentrations at all sites were generally <0.5 μM, with no clear peaks in any season or month. Overall, the lowest values were measured in August and other months showed reasonable spread around the median. Median silicate concentrations were consistently highest at sites 1 and 9, followed by site 5. Water from the River Derwent flows through site 1, then tracks east towards site 9 then site 5. Seasonally, silicate was generally highest in winter when the River Derwent outflow is also greatest.

The Huon Commonwealth Marine Reserve (CMR) covers a broad depth range from the inner continental shelf at about 70 m, to abyssal depths of more than 3000 m. The majority of the area is in deep water. The Tasman Seamounts Marine Reserve that was proclaimed in 1999 has been wholly incorporated into the Huon Commonwealth marine reserve. The reserve contains a cluster of seamounts that appear as cone-shaped submerged mountains, which provide a range of depths for a diversity of plants and animals. The peaks of many of the reserve's seamounts are between 750 m and 1000 m below the sea surface and support endemic species, including large erect corals and sponges. Some of the flora and fauna are hundreds and possibly thousands of years old, making them some of the longest-lived animals on Earth. The reserve also provides an important connection between seamounts of the Indian Ocean and the Tasman Sea. This map of the geomorphology of the Huon CMR was prepared for the NESP Marine Biodiversity Hub Theme D (1) project: National data collation, synthesis and visualisation to support sustainable use, management and monitoring of marine assets.

Understanding the patterns and characteristics of sedimentary deposits on the conjugate Australian-Antarctic margins is critical to reveal the Cretaceous-Cenozoic tectonic, oceanographic and climatic conditions in the basin. However, unravelling its evolution has remained difficult due to the different seismic stratigraphic interpretations on each margin and sparse drill sites. Here, for the first time, we collate all available seismic reflection profiles on both margins and use newly available offshore drilling data, to develop a consistent seismic stratigraphic framework across the Australian-Antarctic basins. We find sedimentation patterns similar in structure and thickness, prior to the onset of Antarctic glaciation, enabling the basin-wide correlation of four major sedimentary units and their depositional history. We interpret that during the warm and humid Late Cretaceous (~83-65 Ma), large onshore river systems on both Australia and Antarctica resulted in deltaic sediment deposition offshore. We interpret that the onset of clockwise bottom currents during the Early Paleogene (~58-48 Ma) formed prominent sediment drift deposits along both continental rises. We suggest that these currents strengthened and progressed farther east through the Eocene. Coevally, global cooling (<48 Ma) and progressive aridification led to a large-scale decrease in sediment input from both continents. Two major Eocene hiatuses recovered by the IODP site U1356A at the Antarctic continental slope likely formed during this pre-glacial phase of low sedimentation and strong bottom currents. Our results can be used to constrain future paleo-oceanographic modelling of this region and aid understanding of the oceanographic changes accompanying the transition from a greenhouse to icehouse world.

Phytoplankton was counted and identified from five sites over the 5-year period. Annual cycles in abundance are available (as cells mL-1), along with detailed species identification. Cell measurements and approximate geometric shape were also recorded for the calculation of biovolume (μL cell-1). Diatoms and dinoflagellates dominated the samples in terms of biomass, however, small cells were also very abundant throughout each year. The data are restricted to an integrated sample from the top 12 m of the water column. Fluorescence profiles elsewhere in this dataset can provide an indication of phytoplankton presence lower in the water column.

Zooplankton was counted and identified from three sites over the 5-year period. The net used (200 m Bongo net) was designed to catch meso-zooplankton with an integrated vertical tow through the water column. One net from each of the paired Bongo samples was analysed and the data expressed as numbers per m3. Copepods dominated the zooplankton, with other groups such as salps, krill, appendicularians, cladocerans, chaetognaths and meroplanktonic larvae being seasonally dominant.

The Tasman Fracture Commonwealth Reserve complements the Port Davey Marine Reserve (encompassing Port Davey, Bathurst Channel and Bathurst Harbour), which was proclaimed by the Tasmanian Government in 2005. It spans the continental shelf, continental slope and deeper water ecosystems south of Tasmania, and is scored by steep canyons. It also encloses other geological features, including steep escarpments and troughs, saddles, basins, and part of a plateau that is over 400 km long and rises up to 3 km above the sea floor. The reserve includes a number of undersea peaks rising to less than 1500 m below the sea surface that provide habitat to deepwater hard corals. These corals provide a structure and habitat for a rich diversity of marine invertebrate animals that live attached corals. This record describes a geomorphology map for the Tasman Fracture CMR that was prepared using bathymetry and backscatter data sourced from CSIRO and Geoscience Australia.