Premium
Carbon isotope fractionation in phytoplankton as a potential proxy for pH rather than for [CO 2 (aq)]: Observations from a carbonate lake
Author(s) -
Wang Shilu,
Yeager Kevin M.,
Lu Weiqi
Publication year - 2016
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10289
Subject(s) - isotopes of carbon , phytoplankton , fractionation , environmental chemistry , isotope fractionation , carbonate , carbon fibers , dissolved organic carbon , stable isotope ratio , chemistry , isotope analysis , isotope , total inorganic carbon , organic matter , total organic carbon , environmental science , oceanography , geology , carbon dioxide , nutrient , materials science , organic chemistry , physics , quantum mechanics , composite number , composite material
The method of reconstructing paleoatmospheric CO 2 levels using carbon isotope signatures of organic matter buried in sediments has been questioned due to the dubious foundation that carbon isotope fractionation during phytoplankton photosynthesis ( ε p ) is controlled primarily by aquatic CO 2 concentration ([CO 2 (aq)]). Consequently, what carbon isotope data from bulk sedimentary organic matter reflects is a puzzle. In this study, we determined the carbon isotope compositions of dissolved inorganic carbon and particulate organic carbon in a lake located in a carbonate area. Partial correlation analysis was employed to distinguish between direct and indirect factors in controlling ε p . The results show that ε p is more closely, and more steadily related with pH than with [CO 2 (aq)], which is in accordance with recent advances in our understanding of the physiology of carbon utilization by phytoplankton for CO 2 andHCO 3 − . Therefore, we propose that carbon isotope fractionation in phytoplankton is more suitable as a proxy of pH than of [CO 2 (aq)]. One advantage of this amendment is that information onHCO 3 − , the main species of carbon uptake by phytoplankton, is likewise included. In the future, culture experiments aiming at revealing the relationship between pH and cellular carbon isotope signatures is necessary to construct a new isotope fractionation formula to couple the different effects of CO 2 andHCO 3 − , which is of critical importance to improve the understanding of carbon isotope fractionation, and to more precisely model pH and CO 2 .