These data were collected on the RV L'Astrolabe (platform code: FHZI) from 28/02/2004 to 04/03/2004 on a trip from Dumont D'Urville to Hobart. Maximum photochemical efficiency of photosystem II (PSII), also called maximum quantum yield of PSII (Fv/Fm), has become one of the most widely utilized fluorescence parameters in phytoplankton research. It represents the potential photochemical efficiency, which is the probability that the light energy captured by the photosynthetic apparatus is being utilized as photochemistry. Fv/Fm has been shown to have an instant response to variations in physical and chemical properties and is interpreted as a diagnostic of the overall health or competence of phytoplankton. Together with the absorption cross section area of PSII and chlorophyll concentration, it can be used to measure primary production (Cheah et al. 2011, Deep Sea Research). Seawater from 3 m depth was supplied continuously from the ship’s clean seawater line. FRR fluorescence yields were measured continuously at 1 minute intervals in dark-adapted state (! 15 minutes dark-adaptation) using a flash sequence consisting of a series of 100 subsaturation flashlets (1.1 μs flash duration and 2.8 μs interflash period) and a series of 20 relaxation flashlets (1.1 μs flash duration and 51.6 μs interflash period).

Declining atmospheric CO2 concentrations are considered the primary driver for the Cenozoic Greenhouse-Icehouse transition, ~34 million years ago. A role for tectonically opening Southern Ocean gateways, initiating the onset of a thermally isolating Antarctic Circumpolar Current, has been disputed as ocean models have not reproduced expected heat transport to the Antarctic coast. Here we use high-resolution ocean simulations with detailed paleobathymetry to demonstrate that tectonics did play a fundamental role in reorganising Southern Ocean circulation patterns and heat transport, consistent with available proxy data. When at least one gateway (Tasmanian or Drake) is shallow (300 m), gyres transport warm waters towards Antarctica. When the second gateway subsides below 300 m, these gyres weaken and cause a dramatic cooling (average of 2–4°C, up to 5°C) of Antarctic surface waters whilst the ACC remains weak. Our results demonstrate that tectonic changes are crucial for Southern Ocean climate change and should be carefully considered in constraining long-term climate sensitivity to CO2.

Thorium-234 samples were collected to determine the particulate organic carbon (POC) export fluxes in two East Antarctica polynyas, Dalton and Mertz. The samples were collected along the water column using the CTD deployed at several stations. The seawater Th-234 data was used in combination with POC:234Th ratios obtained from particulate samples collected using in situ pumps in order to derive the POC fluxes. This record describes Th-234 and U-238_data: sample ID, depth, CTD file, station ID, latitude and longitude, Th-234 concentration and its uncertainty, U-238 concentration and its uncertainty. See linked record for associated POC data from Aurora Australis Voyage 2 2016/17.

This dataset contains physiological measurements collected from sand flathead (Platycephalus bassensis) to examine regional differences in thermal performance between Tasmania’s heavily fished southern population and the more lightly fished northern population. Fish were captured from both regions and acclimated for three weeks under common laboratory conditions before measurements were taken. The dataset includes standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) recorded during acute thermal exposure at 12.5°C, 15°C, and 20°C using intermittent‑flow respirometry. To assess longer‑term thermal tolerance, critical thermal maximum (CTmax) was measured after a 14‑day acclimation to each test temperature. The purpose of the study was to determine whether populations with different histories of fishing pressure exhibit divergent thermal sensitivities and metabolic responses to warming. This information contributes to understanding how exploitation history may influence physiological resilience to climate change in coastal fisheries.

This dataset is derived from a comparative study evaluating six DNA extraction methods for their efficiency in recovering diatom sedimentary ancient DNA (sedaDNA) from Antarctic marine sediments. Sediment samples were collected from two sites: U1536C (Scotia Sea, West Antarctica) and KC02 (Sabrina Coast, Totten Glacier Region, East Antarctica). Each of the six extraction methods was applied to the same set of samples. Following shotgun metagenomic sequencing, the methods were assessed based on metrics such as diatom DNA recovery, average fragment length, and taxonomic diversity. The purpose of the study was to identify the optimal extraction approach for maximizing the yield and quality of diatom sedaDNA, thereby improving its utility for paleoenvironmental reconstruction.