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Sources and composition of high‐molecular‐weight dissolved organic carbon in a southern Louisiana tidal stream (Bayou Trepagnier)
Author(s) -
Engelhaupt Erika,
Bianchi Thomas S.
Publication year - 2001
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.2001.46.4.0917
Subject(s) - dissolved organic carbon , environmental chemistry , lignin , plant litter , organic matter , chemistry , soil water , litter , composition (language) , leachate , decomposition , soil organic matter , nutrient , ecology , environmental science , soil science , biology , organic chemistry , linguistics , philosophy
The composition and cycling of high‐molecular‐weight dissolved organic carbon (HMW‐DOC) were examined in a tidal stream (Bayou Trepagnier) with seasonally high DOC concentrations (1.0–5.6 mM). 13 C nuclear magnetic resonance ( 13 C NMR) was used to examine the bulk chemical composition of natural HMW‐DOC from two field sites over 1.5 yr. The HMW‐DOC at both sites was dominated by aliphatic (41%), carbohydrate (33%), and carboxyl (16%) carbon, with relatively low aromatic carbon abundance (10%). A comparison of 13 C NMR signatures of bayou HMW‐DOC and leachate HMW‐DOC collected from leaf litter and soils revealed that plant litter leachate appears to be a more important source of HMW‐DOM than soil. Dominant sources of HMW‐DOC were likely allochthonous inputs of terrestrial plant litter with periodic inputs of soil organic matter during flooding events. The low aromaticity of bayou HMW‐DOC may reflect the influence of low‐oxygen conditions, which inhibit the decomposition of particulate aromatic macromolecules such as lignin and humic material to HMW‐DOC. Lignin‐phenol biomarker concentrations (del 6 , in mg/100 mg OC) were much lower in HMW‐DOC (1.2) than in plant (5.2) and soil (6.8) organic matter, indicating that a significant fraction of this highly aromatic material was not degraded to HMW‐DOC. Finally, this study demonstrated that lignin and other compounds from terrestrially derived organic matter in sediments and adjacent soils are not a significant source of more soluble moieties that enter the HMW‐DOC pool of the bayou.