The fine-scale depth distribution of major carbon pools and their stable carbon isotopic signatures (delta(13)C) were determined in a cyanobacterial mat (Salin-de-Giraud, Camargue, France) to study early diagenetic alterations and the carbon preservation potential in hypersaline mat ecosystems. Particular emphasis was placed on the geochemical role of extracellular polymeric substances (EPS). Total carbon (C(tot)), organic carbon (C(org)), total nitrogen (N(tot)), total hydrolysable amino acids (THAA), carbohydrates, cyanobacteria-derived hydrocarbons (8-methylhexadecane, n-heptadec-5-ene, n-heptadecane) and EPS showed highest concentrations in the top millimetre of the mat and decreased with depth. The hydrocarbons attributed to cyanobacteria showed the strongest decrease in concentration with depth. This correlated well with the depth profiles of oxygenic photosynthesis and oxygen, which were detected in the top 0.6 and 1.05 mm, respectively, at a high down-welling irradiance (1441 micromol photons m(-2) s(-1)). At depths beneath the surface layer, the C(org) was composed mainly of amino acids and carbohydrates. A resistance towards microbial degradation could have resulted from interactions with diverse functional groups present in biopolymers (EPS) and with minerals deposited in the mat. A (13)C enrichment with depth for the total carbon pool (C(tot)) was observed, with delta(13)C values ranging from -16.3 per thousand at the surface to -11.3 per thousand at 9-10 mm depth. Total lipids depicted a delta(13)C value of -17.2 per thousand in the top millimetre and then became depleted in (13)C with depth (-21.7 to -23.3 per thousand). The delta(13)C value of EPS varied only slightly with depth (-16.1 to -17.3 per thousand) and closely followed the delta(13)C value of C(org) at depths beneath 4 mm. The EPS represents an organic carbon pool of preservation potential during early stages of diagenesis in recent cyanobacterial mats as a result of a variety of possible interactions. Their analyses might improve our understanding of fossilized microbial remains from mat ecosystems.

中文翻译：

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高盐蓝藻垫中的碳库和同位素趋势。

在蓝藻垫（Salin-de-Giraud，Camargue，法国）中确定了主要碳库的精细深度分布及其稳定的碳同位素特征（delta（13）C），以研究早期成岩作用和碳保存潜力在超盐席生态系统中。特别强调了细胞外聚合物（EPS）的地球化学作用。总碳（C（tot）），有机碳（C（org）），总氮（N（tot）），总可水解氨基酸（THAA），碳水化合物，蓝藻衍生的碳氢化合物（8-甲基十六烷，正庚烷- 5烯，正十七烷和EPS在垫的上毫米处显示最高浓度，并随深度降低。归因于蓝细菌的碳氢化合物显示浓度随深度的降低最大。这与氧气的光合作用和氧气的深度分布密切相关，在深度下降辐射（1441微摩尔光子m（-2）s（-1））下，分别在顶部的0.6和1.05 mm处检测到。在表层下面的深处，C（org）主要由氨基酸和碳水化合物组成。对微生物降解的抵抗力可能是由于与生物聚合物（EPS）中存在的各种官能团以及与沉积在垫子中的矿物质的相互作用而引起的。观察到总碳库（C（tot））随深度的（13）C富集，δ（13）C值范围从表面上的-16.3 /千到9-10毫米深度的-11.3 /千。总脂质在最高毫米处的delta（13）C值为-17.2 /千，然后在（13）C中逐渐耗尽（-21.7至-23.3 /千）。EPS的delta（13）C值随深度变化很小（-16.1至-17.3 /千），并且在4mm以下的深度处紧随C（org）的delta（13）C值。由于各种可能的相互作用，EPS代表了最近的蓝藻垫在成岩早期阶段的潜在保存有机碳库。他们的分析可能会增进我们对垫层生态系统中化石微生物残留的理解。