Causes and biogeochemical implications of regional differences in silicification of marine diatoms

摘要: [1] Diatoms facilitate the export of organic carbon and associated nutrient elements in ocean because their dense opaline silica shells provide ballast to sinking particles. Marine ecosystem models generally assume that cellular silicification is either constant or varies solely due physiological responses. Using a cell-specific technique, synchrotron-based X-ray fluorescence (SXRF) microscopy, we show diatom cells cold, high-silicic-acid waters Antarctic Zone Southern Ocean (SOAZ) had 6 times more Si per volume than did those inhabiting warm, low-silicic-acid eastern equatorial Pacific (EEP). Ratios Si:P Si:S differed less this P S concentrations were higher SOAZ cells. Resulting differences excess density frustule surface area-to-volume ratios should result efficient removal slower dissolution biogenic compared EEP. Moreover, difference between densities diatoms nondiatoms was 15-fold greater Several possible causes regional are evaluated. Differences cell regions additions silicic acid iron minor effects on silicification. Instead, varied substantially among morphological types within each region, suggesting community composition largely determined these regions. We suggest ecological processes may cause much larger systematic temporal stoichiometry currently accommodated by models.