Glacial Ice Melting Stimulates Heterotrophic Prokaryotes Production on the Getz Ice Shelf in the Amundsen Sea, Antarctica. Issue 19 (29th September 2022)

• Record Type: Journal Article
• Authors: Min, Jun‐Oh; Kim, Sung‐Han; Jung, Jinyoung; Jung, Ui‐Jung; Yang, Eun Jin; Lee, SangHoon; Hyun, Jung‐Ho
• Is Part Of: Geophysical research letters. Volume 49:Issue 19(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-29
• Subjects: bacterial production -- microbial loop -- Getz Ice Shelf -- DOC -- meltwater -- Amundsen Sea; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL097627
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Extensive oceanographic data sets were combined with microbiological parameters to elucidate the tight coupling between glacial meltwater and heterotrophic bacterial production (BP) on the Getz Ice Shelf (GtzIS) in the Amundsen Sea. BP in the eastern GtzIS (EG; 85.8 pM Leu. h −1 ), where basal glacier meltwater upwells, was significantly higher than BP measured in the western GtzIS (WG; 50.6 pM Leu. h −1 ) and the Amundsen Sea Polynya (ASP; 27.8 pM Leu. h −1 ). BP in the EG accounted for 49% of primary production, which was greater than that of the WG (10%) and ASP (9.2%). Enhanced BP in the eastern GtzIS was not coupled with phytoplankton biomass, but correlated significantly with the freshwater fraction containing meltwater‐derived dissolved organic carbon (MW‐DOC). These results suggest that warming‐induced glacier melting weakens carbon sequestration efficiency in Antarctic coastal waters by stimulating heterotrophic metabolism that converts MW‐DOC to CO2 . Plain Language Summary: The Getz Ice Shelf (GtzIS) in the Amundsen Sea, the third‐largest ice shelf (34, 018 km 2 ) on the West Antarctic Ice Sheet, is regarded as a hot spot for producing large amount of glacier meltwater (144.9 ± 14 Gt yr −1 ). In general, the amount of dissolved organic carbon (DOC) from terrestrial sources is negligible in Antarctic waters, making DOC supplied by phytoplankton a major carbon source for heterotrophic bacteria growth. Although Antarctica's glacial ice shelves are presumably a large reservoir of organic carbon (ca. 5.5 Pg C), little is known about the effect of glacial melting on the supply of DOC available to heterotrophic bacteria. On the eastern GtzIS, where glacial meltwater upwells to the surface water column, heterotrophic bacteria production has no significant positive relationship with phytoplankton biomass, but is positively correlated with freshwater fraction. This suggests that DOC in glacial meltwater, rather than phytoplankton, provides DOC to support enhanced bacteria production. Our results imply that global warming–related increases in glacial meltwater may stimulate heterotrophic bacterial metabolism that respires DOC to CO2, thereby reducing carbon sequestration efficiency in Antarctic coastal waters. Key Points: Unlike the sea‐ice melting system, enhanced bacterial production (BP) in the eastern Getz Ice Shelf (GtzIS) was uncoupled with phytoplankton biomass Dissolved organic carbon in glacier meltwater likely stimulates BP on the eastern GtzIS Warming‐induced glacial melting may weaken carbon sequestration in the Antarctic Ocean by stimulating heterotrophic bacterial metabolism