Study site and sampling strategy
Deception Island (62°58′ S, 60°39′ W) is a complex stratovolcano located in the South Shetland Islands, Bransfield Strait, near the Antarctic Peninsula. A past eruption occurring approximately 10,000 years ago collapsed the central part of the island giving rise to a flooded caldera called Port Foster Bay, 9 km in diameter (Baker et al., 1975). Fumaroles are found mainly at Fumarole Bay (FB), Whalers Bay (WB), and Pendulum Cove (Fermani et al., 2007; Geyer et al., 2019), and they are distributed mostly in submerged and partially submerged regions (intertidal zones), with temperatures varying from 40-60°C in WB and 80-100°C in FB (Rey et al., 1995; Somoza et al., 2004). Carbon dioxide and hydrogen sulfide gases are emitted by fumaroles and are oxidized to products such as sulfite and sulfate (Somoza et al., 2004; Zhang & Millero, 1993).
Sampling was performed during the XXXII Brazilian Antarctic Expedition (December 2013 to January 2014), with logistical support from the polar vessel NPo. Almirante Maximiano. We collected surface sediment samples (ca. 5 cm) in fumaroles and glaciers at geothermally active sites in FB (62°58’02.7” S, 60°42’ 36.4” W) and WB (62°58’45.1” S, 60°33’27.3” W) (Figure 1a and 1b), with temperatures between 0 and 98oC. At each site, we obtained samples from three different points within the temperature gradient, and triplicates were performed for each collected point, totaling 18 sediment samples. Points A and B were defined as samples collected in fumaroles, while point C samples were collected from the glacier, few cm below the glacier’s edge (Figure 1c and 1d). The point FBA was the hottest fumarole, measuring 98oC at the sediment surface (ca. 20 cm). Distances between fumaroles and glaciers at each site were approximately 15 m, and the WB and FB transects were approximately 10 km apart. All fumaroles were in the intertidal zone, except for point B from FB, which was in the subtidal zone (submerged at 50 cm depth in the water column). Samples were stored at -20 °C until arrival at the University of São Paulo, Brazil in April 2014.