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.