Control of acid polysaccharide production and 234Th and POC export fluxes by marine organisms

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Read Full Article (file size: 138690 bytes) Cited by GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 2, 1044, doi:10.1029/2002GL016046, 2003 Control of acid polysaccharide production and ²³⁴Th and POC export fluxes by marine organisms Peter H. Santschi Laboratory for Oceanographic and Environmental Research, Department of Oceanography, Texas A&M University, Galveston, TX, USA Chin-Chang Hung Laboratory for Oceanographic and Environmental Research, Department of Oceanography, Texas A&M University, Galveston, TX, USA Gary Schultz Laboratory for Oceanographic and Environmental Research, Department of Oceanography, Texas A&M University, Galveston, TX, USA Nicolas Alvarado-Quiroz Laboratory for Oceanographic and Environmental Research, Department of Oceanography, Texas A&M University, Galveston, TX, USA Laodong Guo International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, USA Jay Pinckney Department of Oceanography, Texas A&M University, College Station, TX, USA Ian Walsh College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA Abstract Ratios of particulate organic carbon (POC) to particulate ²³⁴Th activities (POC/²³⁴Th) in the ocean are used to determine the POC export flux, and thus, the power of the biological pump. In order to understand the main reasons why this ratio frequently varies as a function of depth, size, and kind (suspended vs. sinking particles), we measured vertical profiles in a cold core ring and warm core ring in the Gulf of Mexico in May 2001. Here we show that particulate ²³⁴Th/POC ratios in the Gulf of Mexico are positively correlated to the content of different Th(IV)-binding polysaccharide fractions (uronic acids, total acid polysaccharides, total polysaccharides) in both suspended and sinking particles as well as to prymnesiophyte abundance, but negatively correlated to bacterial production. Variations in acid polysaccharide compounds, produced by both algae and bacteria, but degraded only by bacteria, can account for observed variations in POC/²³⁴Th ratios seen in the ocean. Published 21 January 2003. Index Terms: 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 4860 Oceanography: Biological and Chemical: Radioactivity and radioisotopes; 4807 Oceanography: Biological and Chemical: Chemical speciation and complexation. Read Full Article (file size: 138690 bytes) Cited by Citation: Santschi, P. H., C. Hung, G. Schultz, N. Alvarado-Quiroz, L. Guo, J. Pinckney, and I. Walsh (2003), Control of acid polysaccharide production and ²³⁴Th and POC export fluxes by marine organisms, Geophys. Res. Lett., 30(2), 1044, doi:10.1029/2002GL016046. Copyright 2003 by the American Geophysical Union.

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