The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum
|Author(s)||Xiong Zhifang1, Li Tiegang1, Algeo Thomas2, 3, 4, Doering Kristin5, 6, Frank Martin6, Brzezinski Mark A.7, 8, Chang Fengming1, Opfergelt Sophie9, Crosta Xavier10, Jiang Fuqing1, Wan Shiming1, Zhai Bin11|
|Affiliation(s)||1 : Chinese Acad Sci, Key Lab Marine Geol & Environm, Inst Oceanol, Qingdao, Peoples R China.
2 : Univ Cincinnati, Dept Geol, Cincinnati, OH USA.
3 : China Univ Geosci, State Key Lab Biogeol & Environm Geol, Wuhan 430074, Peoples R China.
4 : China Univ Geosci, State Key Lab Geol Proc & Mineral Resource, Wuhan 430074, Peoples R China.
5 : Univ Kiel, Inst Geosci, Kiel, Germany.
6 : GEOMAR Helmholtz Ctr Ocean Res Kiel, Kiel, Germany.
7 : Univ Calif Santa Barbara, Marine Sci Inst, Santa Barbara, CA 93106 USA.
8 : Univ Calif Santa Barbara, Dept Ecol Evolut & Marine Biol, Santa Barbara, CA 93106 USA.
9 : Catholic Univ Louvain, Earth & Life Inst, Louvain La Neuve, Belgium.
10 : Univ Bordeaux, UMR CNRS EPOC 5805, Pessac, France.
11 : Minist Land & Resources, Qingdao Inst Marine Geol, Key Lab Marine Hydrocarbon Resource & Geol, Qingdao, Peoples R China.
|Source||Paleoceanography (0883-8305) (Amer Geophysical Union), 2015-07 , Vol. 30 , N. 7 , P. 803-823|
|WOS© Times Cited||20|
The cause of massive blooms of Ethmodiscus rex laminated diatom mats (LDMs) in the eastern Philippine Sea (EPS) during the Last Glacial Maximum (LGM) remains uncertain. In order to better understand the mechanism of formation of E. rex LDMs from the perspective of dissolved silicon (DSi) utilization, we determined the silicon isotopic composition of single E. rex diatom frustules (delta Si-30(E.rex)) from two sediment cores in the Parece Vela Basin of the EPS. In the study cores, delta Si-30(E.rex) varies from -1.23 parts per thousand to -0.83 parts per thousand (average -1.04 parts per thousand), a range that is atypical of marine diatom delta Si-30 and that corresponds to the lower limit of reported diatom delta Si-30 values of any age. A binary mixing model (upwelled silicon versus eolian silicon) accounting for silicon isotopic fractionation during DSi uptake by diatoms was constructed. The binary mixing model demonstrates that E. rex dominantly utilized DSi from eolian sources (i.e., Asian dust) with only minor contributions from upwelled seawater sources (i.e., advected from Subantarctic Mode Water, Antarctic Intermediate Water, or North Pacific Intermediate Water). E. rex utilized only similar to 24% of available DSi, indicating that surface waters of the EPS were eutrophic with respect to silicon during the LGM. Our results suggest that giant diatoms did not always use a buoyancy strategy to obtain nutrients from the deep nutrient pool, thus revising previously proposed models for the formation of E. rex LDMs.