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Long‐term photochemical and microbial decomposition of wetland‐derived dissolved organic matter with alteration of 13C:12C mass ratio
Author(s) -
Vähätalo Anssi V.,
Wetzel Robert G.
Publication year - 2008
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.2008.53.4.1387
Subject(s) - dissolved organic carbon , environmental chemistry , decomposition , mineralization (soil science) , organic matter , leachate , chemistry , carbon fibers , total organic carbon , bioassay , juncus , wetland , ecology , nitrogen , biology , materials science , organic chemistry , composite number , composite material
We investigated the long‐term photochemical and microbial decomposition of biologically recalcitrant humic‐like dissolved organic matter (DOM) leached from a vascular wetland plant, the common rush ( Juncus effusus ). Although the leachate would have been characterized as biologically recalcitrant by short‐term (<14 d) bioassays, microbes decomposed 51% of its organic carbon in 898 d with a first‐order biological decomposition coefficient of 0.0008 d ‐1 in darkness. Solar radiation exposure accelerated the decomposition of leachate. Under 459‐d exposure to surface solar radiation, up to 90% of organic carbon was mineralized. During the exposure, the photochemical reactions preferentially mineralized the 12 C fraction of organic carbon and enriched the 13 C of organic carbon by 6% in the residual leachate. Solar radiation also decomposed nearly completely (up to 99.7%) chromo‐ and fluorophores of DOM. A 439‐d bioassay following the solar radiation exposure resulted in up to 97.3% mineralization of organic carbon. Solar radiation together with microbial metabolism can completely mineralize at least some forms of wetland‐derived DOM in surface waters with sufficiently long residence times.