Organic-walled microfossils from the north-west Weddell Sea, Antarctica: records from surface sediments after the collapse of the Larsen-A and Prince Gustav Channel ice shelves

• Published in: Antarctic Science
• Main Authors: Pieńkowski, Anna J., Marret, Fabienne, Scourse, James D., Thomas, David N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2013
• Subjects: Antarc*; Antarctic; Antarctic Peninsula; Antarctic Science; Antarctica; Ice Shelf; Ice Shelves; Southern Ocean; Weddell Sea
• Online Access: http://dx.doi.org/10.1017/s0954102012001186; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102012001186

Abstract Surface sediments from six box cores along the north-eastern Antarctic Peninsula document the dinoflagellate cyst (= dinocyst) and other non-pollen palynomorph (NPP) content soon after overlying ice shelves collapsed. Prince Gustav Channel (PGC) and Larsen-A (LA) areas exhibited markedly different dinocyst abundances, concentrations being low in LA (0–20 cysts g -1 ) and high in PGC (2600–9100 cysts g -1 , average: c. 3800 cysts g -1 ). Since similar water masses impact both areas, differences may be due to low biological productivity, limited sediment accumulation, and/or restricted fine-grain deposition at Larsen-A. Islandinium minutum (Harland & Reid in Harland et al .) Head et al . dominated dinocyst assemblages, occurring as both excysted and encysted forms (lesser abundance). Other taxa ( Echinidinium cf. transparantum Zonneveld, Impagidinium pallidum Bujak, Bitectatodinium tepikiense Wilson, Operculodinium centrocarpum Wall & Dale, Brigantedinium spp., Selenopemphix antarctica Marret & de Vernal, Polykrikos? sp. A, and Polykrikos schwartzii Bütschli) were rare. Such assemblage composition is unusual compared to previously published Southern Ocean data, but may be specific to ice shelf and/or recently ice-free environments. Alternatively, it may be attributable to excessive production facilitated by environmental factors and/or abundant food, or similar cyst morphologies produced by different dinoflagellates. Accompanying NPPs included zooplankton remains, acritarchs, and freshwater algae. Tintinnid loricae were most abundant (max. 800 g -1 ), followed by foraminiferal linings (max. 320 g -1 ), and the acritarch Palaeostomocystis fritilla (Bujak) Roncaglia (max. 150 g -1 ). Collectively, NPPs were more abundant in PGC compared to LA samples.