δ18Oara profile for shelled pteropod calcification depth estimate based on seawater salinity and temperature measured by Argo floats. The oxygen isotopic composition of pteropod shells (δ18Optero) was compared to the δ18Oara at different depths. The calcification depth is defined as the depth where the values of δ18Optero and δ18Oara were equal within their respective uncertainties. Shelled pteropods are at risk from ocean acidification, with known effects on their shell durability and calcification. Pteropods typically form their aragonitic shells over specific depth ranges known as the ‘calcification depth’, which varies depending on species and habitats. Some Southern Ocean waters are already undersaturated with respect to aragonite and this could negatively affect shelled pteropods. However, the calcification depths of the pteropods have not been determined nor used to infer consequences of changing seawater carbonate chemistry in the Southern Ocean. In this study, we analysed the stable oxygen isotopic composition of Limacina rangii shells, collected by sediment traps in the subantarctic zone, to estimate their calcification depth. Shallow calcification depths (13-126 m) were detected in summer-autumn, while L. rangii calcified their shells deeper in the water column during winter-spring, with an average maximum calcification depth of 525 m. Recent shoaling of the aragonite saturation horizon is likely to negatively affect pteropods that calcify their shells in deep water. Such shoaling is likely to reduce shell formation and threaten population viability.

Temperature loggers have been deployed at a range of sites statewide in waters ranging between 6 and 22m depth. From 2012, 29 sites around Tasmania are being monitored. This record shows data collected from 2004 up to March 2025. Data is still being collected (July 2025) and will be added to this collection as it becomes available.

Sustainable finfish aquaculture is dependent on a benthic environment that can assimilate and process farm particulate wastes. In Macquarie Harbour, bottom and mid water Dissolved Oxygen levels have reached very low levels, which is associated with an increase in the presence of bacterial mats and a significant decline in the abundance and diversity of benthic fauna. Dissolved Oxygen levels are a major determinant of the response of benthic communities in the harbour over timescales of months to years. This dataset consists of data collected by the real-time dissolved oxygen (DO) monitoring system deployed at three locations in Macquarie Harbour, Tasmania. Loggers were originally established under the Sense-T program, continued under FRDC project 2016-067, and deployed and maintained by IMAS. The system consists of 3 strings of acoustically telemetered, optical fluorescence DO, temperature and depth sensors (VEMCO, Bedford, Canada) which measure DO (% saturation) and temperature (°C) across a depth gradient. Data collected from 01-01-2017 to 19-04-2017 consists of data was collected using the first generation of sensors, while data subsequent to 03-06-2017 was collected using a new generation of tags which contain a tilt instead of a depth sensor.