Potential of Organic Matter Generation of Microbial Mats Based on Biogeochemical Proxies in Hypersaline Lagoons of Rio de Janeiro, Brazil

Abstract

Microbial mats are biosedimentary structures formed by a bacterial consortium of autotrophic and heterotrophic bacteria, whose primary productivity generates Amorphous Organic Matter. The aim of this paper was to evaluate the organic matter production of microbial mats using biogeochemical proxies and establishing relationship with superficial sediments. High values of total organic carbon (TOC), total sulfur (S), total inorganic carbon (TIC) and biopolymers concentrations (lipids,proteins, carbohydrates) in the microbial mats, when compared to the sediments, shows high bacterial productivity and local production of the organic matter. The cluster analyzes defined two Palynofacies Associations based on the origin and quality of the organic matter. Two groups of samples highlighted the compositional differences and the potential of preservation of the organic matter between microbial mats and sediments. Palynofacies 1, was represented by sediment samples and sand microbial mat, which is characterized of bacterially derived amorphous organic matter (Bacterial AOM) and well preserved non-opaque phytoclasts. Palynofacies 2, composed of the samples of microbial mats characterized mainly by EPS (Bacterial AOM precursor) with high fluorescence indicating a highly productive system generator of Type I organic matter. The occurrence of microbial mats can contribute significantly to the production of type oil-prone organic matter in the environments that support its development if the carbonate precipitation accompanies the sedimentation processes.