Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

• Published in: Paleoceanography 2014-04, Vol.29 (4), p.328-343
• Main Authors: Panizzo, Virginia, Crespin, Julien, Crosta, Xavier, Shemesh, Aldo, Massé, Guillaume, Yam, Ruth, Mattielli, Nadine, Cardinal, Damien
• Format: Article
• Language: English
• Subjects: Bacillariophyceae; Biogeochemistry; Climatology; diatom bound carbon isotopes; diatoms; Earth Sciences; Fractionation; Fragilariopsis curta; Fragilariopsis cylindrus; Fragilariopsis kerguelensis; Holocene; Ice; Ice environments; Marine; Nutrient utilization; Ocean, Atmosphere; Oceanography; Oceans; Paleoclimate science; Plankton; Sciences of the Universe; Sea ice; seasonal ice zone; Silica; silicon isotopes; Southern Ocean
• ISSN: 0883-8305; 2572-4517; 1944-9186; 2572-4525
• DOI: 10.1002/2014PA002609

Combined high‐resolution Holocene δ30Sidiat and δ13Cdiat paleorecords are presented from the Seasonal Ice Zone, East Antarctica. Both data sets reflect periods of increased nutrient utilization by diatoms during the Hypsithermal period (circa 7800 to 3500 calendar years (cal years) B.P.), coincident with a higher abundance of open water diatom species (Fragilariopsis kerguelensis), increased biogenic silica productivity (%BSi), and higher regional summer temperatures. The Neoglacial period (after circa 3500 cal years B.P.) is reflected by an increase in sea ice indicative species (Fragilariopsis curta and Fragilariopsis cylindrus, up to 50%) along with a decrease in %BSi and δ13Cdiat (< −18‰ to −23‰). However, over this period, δ30Sidiat data show an increasing trend, to some of the highest values in the Holocene record (average of +0.43‰). Competing hypotheses are discussed to account for the decoupling trend in utilization proxies including iron fertilization, species‐dependent fractionation effects, and diatom habitats. Based on mass balance calculations, we highlight that diatom species derived from the semi‐enclosed sea ice environment may have a confounding effect upon δ30Sidowncore compositions of the seasonal sea ice zone. A diatom composition, with approximately 28% of biogenic silica derived from the sea ice environment (diat‐SI) can account for the increased average composition of δ30Sidiat during the Neoglacial. These data highlight the significant role sea ice diatoms can play with relation to their export in sediment records, which has implications on productivity reconstructions from the seasonal ice zone. Key Points A decoupling in nutrient utilization proxies occurs in the Neoglacial Sea‐ice derived diatoms are discussed as a potential explanatory factor A departure from the application of nutrient proxies is discussed