Abstract
Deception Island is amongst the most active volcanoes in the Southern Ocean, with over 20 explosive eruptions in the last ca. 200 years. The eruption that formed the caldera at Deception Island occurred 3980 ± 125 calendar years Before Present, and it is the largest eruptive event documented in Antarctica during Holocene. Since then, post-caldera volcanic activity has comprised many scattered eruptive vents across the island. Mortality of benthic organisms has been reported during the most recent eruptions occurred on the island, in 1967, 1969, and 1970 Common Era (CE), with very low abundances of organisms during the 1967–1973 CE period. Within the sea-flooded part of the caldera depression, named Port Foster, a submarine volcanic axis with several volcanic cones is observed. An interdisciplinary team sampled the best morphologically preserved volcanic edifice within Port Foster, the so-called Stanley Patch. Geophysical data traced the volcano and characterized its morphology and inner structure. Underwater scuba sampling allowed to acquire sediment and rock samples, photographs and video images of the benthic organisms and seascape. Morphology of Stanley Patch cone and textural characteristics of the collected pyroclastic rocks indicate that the volcanic edifice was originated during an explosive eruption. Furthermore, the lack of palagonitization, quenched pyroclast margins, and hyaloclastite deposits indicate that this cone has formed on-land, before the caldera floor became inundated by the seawater, highlighting the complex intra-caldera evolution of Deception Island. A sediment core from the crater was collected for sedimentological, and geochemical analysis. Antarctic climate and seasonal sea ice, together with organic degradation due to high sedimentation rates, explain the low total organic carbon data measured. The volcanic history of the island has probably avoided the development of a stable benthic community over time, similar to other Antarctic shallow communities. Moreover, the current geomorphological conditions still shape different benthic communities than in the surrounding coastal ecosystems. Stanley Patch, and the whole Port Foster, provide a natural laboratory for benchmarking the reestablishment of benthic communities on a volcanic-influenced shallow marine environment, offering relevant data for future studies evaluating global climate change effects on the Antarctic seabed.
Highlights
Deception Island is amongst the most active volcanoes in the Southern Ocean, with over 20 explosive eruptions in the last ca. 200 years
Deception Island is located at the southwestern end of the Bransfield Strait, an actively extending young marginal basin between the Antarctic Peninsula and South Shetland Islands
The apparent absence of typical petrologic features of submarine volcanic eruption in the studied samples such as palagoniti zation, quenched rims, and hyaloclastites suggest that Stanley Patch formed under “dry”-subaerial conditions, and subsequently partially eroded
Summary
Deception Island is amongst the most active volcanoes in the Southern Ocean, with over 20 explosive eruptions in the last ca. 200 years. While in shallow coastal areas of Antarctica, the benthic communities are mainly influenced by ice disturbance (Smale 2008), in Deception Island, factors such as volcanic activity and sedimentation may impose the distribution and abundance of macroinvertebrates (Brierley, 1999; Barnes et al, 2008). The volcanic and magmatic evolution of the island is marked by a large eruption that occurred 3980 ± 125 calibrated years Before Present (BP) (Antoniades et al, 2018) This event led to the catastrophic collapse and sinking of the major volcanic edifice that generated the current caldera (Rey et al, 1995; Smellie, 2002). Some of these volcanic edifices, mainly located at the southern part of the bay, are morphologically well-preserved and rise up to more than 50 m from the seafloor
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