Premium
Carbon pools and isotopic trends in a hypersaline cyanobacterial mat
Author(s) -
WIELAND A.,
PAPE T.,
MÖBIUS J.,
KLOCK J.–H.,
MICHAELIS W.
Publication year - 2008
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2007.00138.x
Subject(s) - cyanobacteria , carbon fibers , total organic carbon , microbial mat , environmental chemistry , chemistry , heptadecane , total inorganic carbon , isotopes of carbon , diagenesis , dissolved organic carbon , nitrogen , photosynthesis , botany , mineralogy , carbon dioxide , biology , bacteria , organic chemistry , materials science , composite number , composite material , genetics
The fine‐scale depth distribution of major carbon pools and their stable carbon isotopic signatures (δ 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 µmol 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 δ 13 C values ranging from –16.3‰ at the surface to –11.3‰ at 9–10 mm depth. Total lipids depicted a δ 13 C value of –17.2‰ in the top millimetre and then became depleted in 13 C with depth (–21.7 to –23.3‰). The δ 13 C value of EPS varied only slightly with depth (–16.1 to –17.3‰) and closely followed the δ 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.