INVESTIGADORES
LARA Ruben Jose
artículos
Título:
Molecular evidence for lignin degradation in sulfate-reducing mangrove sediments (Amazônia, Brazil).
Autor/es:
DITTTMAR, THORSTEN; LARA, RUBÉN JOSÉ
Revista:
GEOCHIMICA ET COSMOCHIMICA ACTA
Editorial:
Elsevier
Referencias:
Lugar: Amsterdam; Año: 2001 p. 1417 - 1428
ISSN:
0016-7037
Resumen:
&amp;amp;amp;lt;!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0pt; margin-bottom:.0001pt; mso-pagination:none; text-autospace:none; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-TRAD; mso-fareast-language:ES;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --&amp;amp;amp;gt; <!-- /* Font Definitions */ @font-face {font-family:Universal-GreekwithMathPi; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0pt; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Molecular lignin analyses have become a powerful quantitative approach for estimating flux and fate of vascular plant organic matter in coastal and marine environments. The use of a specific molecular biomarker requires detailed knowledge of its decomposition rates relative to the associated organic matter and its structural diagenetic changes. To gain insight into the poorly known processes of anaerobic lignin diagenesis, molecular analyses were performed in the sulfate-reducing sediment of a north Brazilian mangrove. Organic matter in samples representing different diagenetic stages (i.e., fresh litter, a sediment core, and percolating water) was characterized by alkaline CuO oxidation for lignin composition, element (C, N), and stable carbon isotope analyses. On the basis of these results and on a balance model, long-term in situ decomposition rates of lignin in sulfate-reducing sediments were estimated for the first time. The half-life (T1/2) of lignin derived from mangrove leaf litter (mainly Rhizophora mangle) was ;150 yr in the upper 1.5 m of the sediment. Associated organic carbon from leaf tissue was depleted to ;75% within weeks, followed by a slow mineralization in the sediment (T1/2 ' 300 yr). Unlike the known pathways of lignin diagenesis, even highly degraded lignin did not show any alterations of the propyl or methoxyl side chains, as evident from stable acid to aldehyde ratios and the proportion of methoxylated phenols (vanillyl and syringyl phenols). Aromatic ring cleavage is probably the principal mechanism for lignin decay in the studied environment. Cinnamyl phenols were highly abundant in mangrove leaves and were rapidly depleted during early diagenesis. Thus, the cinnamyl to vanillyl ratio could be used as a tracer for early diagenesis even under the sulfate-reducing conditions. Syringyl phenols were removed from dissolved organic matter in interstitial water, probably by sorption onto the sediment. Suspended organic matter in a mangrove creek showed a different lignin signature than its source, namely sedimentary organic matter or mangrove litter, with clear evidence for propyl side chain oxidation. This was probably attributable to erosion of aerated thin sediment surface layers during mangrove inundation. Although particulate and dissolved organic matter in the mangrove creek have a common source, their compositional patterns were different, because of different pathways of release, degradation, and transport to the creek.