Early diagenesis of carbohydrates and lignin in mangrove sediments subject to variable redox conditions (French Guiana)

Abstract

A comparative study of lignin and neutral carbohydrate compositions, combined with C, N and ␦ 13 C analyses, was carried out on sedimentary cores, and on various vascular plant species collected in mangrove swamps of French Guiana. The main purpose of this study was to assess the diagenesis of carbohydrates and lignin in brackish to hypersaline fine-grained mangrove sediments characterized by great changes in redox conditions. Distribution of carbohydrates in sediments reflects both the lability of these compounds and their efficient recycling. They are subject to selective degradation, cellulosic glucose and xylose appearing to be the two most labile neutral sugars. In contrast a relative increase in arabinose, rhamnose, fucose and hemicellulosic glucose between plants and sediments, suggests that they may be more refractory and/or that they also derive from microbial synthesis. The total carbon from lignin-derived phenols is higher in sediments than in mangrove plants as a consequence of their rather refractory character. Nevertheless, evidence of lignin decomposition was found to be independent of local environmental conditions. The various redox processes that occur in mangrove sediments depend on plant species, stages in forest development and season. Different redox conditions induce different mechanisms for the decomposition of lignin and thus induce changes in phenol distributions. At depth, in most mangroves, an increase in (Ad/Al) v ratios and in deoxy sugars (fucose and rhamnose) content was significantly correlated with increased proportions of oxidized allochthonous organic debris deriving from the Amazonian detrital discharge, thus suggesting a specific source effect rather than a diagenesis induced change. Therefore, this study illustrates that both lignin and cellulose, derived from vascular plant debris, can be degraded in waterlogged mangrove sediments, and that their distribution depends on environmental conditions.

Concentrations and Fractionation of Carbon, Iron, Sulfur, Nitrogen and Phosphorus in Mangrove Sediments Along an Intertidal Gradient (Semi-Arid Climate, New Caledonia)

“…C values of the leaves of the two studied mangrove species and Salicornia are consistent with those found in the literature [36,37]. TOC, C/S, HI and OI measured in sediment cores of the different stands are displayed in Figure 4.…”

Composition, production, and loss of carbohydrates in subtropical shallow subtidal sandy sediments: Rapid processing and long‐term retention revealed by 13C‐labeling

“…To our knowledge, although studies have looked at carbohydrate composition of temperate shallow sediments (Liebezeit 1987;Khodse et al 2008) and diagenesis in tropical intertidal muds (Marchand et al 2005), this is the first to examine the composition, production, and loss of carbohydrates in shallow subtidal sands in the subtropics. Furthermore, this is the first application of a HPLC-IRMS technique (Boschker et al 2008) to monitor carbon transfer to and from carbohydrates in a long-term (30 d) in situ 13 Clabeling experiment.…”

“…Carbohydrate composition and concentration can be further affected by nutrient availability (Underwood et al 2004;Cook et al 2007) and environmental conditions (e.g., light and salinity) that influence growth of carbohydrate sources (e.g., algae; Smith and Underwood 2000;Perkins et al 2001;Abdullahi et al 2006). Because of the competing influences on carbohydrate composition, spectra are best interpreted in combination with additional sediment characteristics such as C : N ratios (Khodse et al 2008) and natural abundance stable isotope ratios (Marchand et al 2005).…”

Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions

“…Studies using a combination of these bulk properties with molecular biomarker techniques (as the present study adopted) have been limited however. Boschker et al (1995) apply such methodologies in Lake Gooimer, and Marchand et al (2005) apply a similar approach to study the sediment in a mangrove system. Relatively comprehensive studies using multiple markers are reported in the Amazon system (Bernardes et al, 2004;Hedges et al, 1994).…”