Water temperature, averaged across the water column, in Storm Bay followed a distinct seasonal cycle each year, reaching a low of 9 °C and a high of ~ 19 °C. Warmest temperatures were in February, followed by a gradual cooling throughout autumn to a winter minimum in August, then increasing again during spring. Across the sites, the median temperature varied little, with site 3, the most marine of the sites, showing the least spread in values. Median salinity varied little across Storm Bay, being slightly higher at sites 3 and 6, highlighting the marine nature of site 3 and the patterns of seawater circulation in Storm Bay. The lowest salinities were recorded at site 1, where less saline surface waters flow into the bay from the Derwent Estuary. Seasonally, salinity was highest in autumn, with slightly fresher water present in Storm Bay in spring. Some lower salinity values were recorded in July and August, suggesting the presence of less saline subantarctic water flowing into the bay, or freshwater flow from the Derwent. Glider transects show slight lower salinity in summer, then mild stratification in autumn to spring, especially in the shallow regions near the mouth of the Derwent.
Temperature, salinity, fluorescence, and dissolved oxygen were measured at each site using a Seabird SBE 19 plus CTD (full water column profile) and/or a YSI 6600 V2 Sonde CTD (profile to 30 m). The CTD was programed to measure parameters every second on the down and upcasts. The data were depth averaged to every 0.5 m and only the upcasts were used as they showed less ‘noise’ in the profiles.