Premium
Transformations of carbon in anoxic marine sediments: Implications from Δ 14 C and δ 13 C signatures
Author(s) -
Komada Tomoko,
Polly Jonathon A.,
Johnson Leah
Publication year - 2012
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 - 10.4319/lo.2012.57.2.0567
Subject(s) - dissolved organic carbon , anoxic waters , environmental chemistry , particulates , chemistry , carbon fibers , isotopes of carbon , organic matter , total organic carbon , incubation , sediment , isotopic signature , total inorganic carbon , carbon cycle , sulfate , mineralogy , carbon dioxide , stable isotope ratio , geology , ecology , ecosystem , biology , organic chemistry , paleontology , biochemistry , materials science , physics , quantum mechanics , composite number , composite material
Organic‐rich nearshore sediment was incubated in sealed vessels under sulfate‐reducing conditions to investigate the mechanism of dissolved organic carbon (DOC) production in marine sediments. Concentrations and isotopic signatures ( δ 13 C and Δ 14 C) of particulate organic carbon (POC), DOC, dissolved inorganic carbon (DIC), and particulate inorganic carbon (PIC) were monitored for 130 d. POC solubilization was largely counterbalanced by respiration, resulting in a net increase in DIC of > 35 mmol L −1 . Net accumulation of DOC was relatively muted, yet significant, at ∼ 0.04 mmol L −1 . All carbon pools exhibited distinct δ 13 C and Δ 14 C signatures prior to the incubation. Once the incubation began, these isotopic values varied with time, reflecting exchanges of isotopically distinct moieties across carbon pools. The 14 C‐enriched (modern) component of bulk POC was selectively solubilized into DOC, and the majority of this DOC was rapidly respired to DIC. However, net accumulation of DOC was accompanied by a drop in Δ 14 C, suggesting that during selective solubilization of the younger component of bulk POC, there was concomitant solubilization of pre‐aged organic matter that subsequently accumulated as DOC. PIC was minor in terms of pool size, but likely played a critical role in determining the δ 13 C signature of pore‐water DIC through isotope exchange.