Fatty acids, hydrocarbons, sterols and alkenones of microbial mats from coastal ecosystems of the ebro delta

Abstract Fatty acids, hydrocarbons, ketones, alcohols and sterols have been analyzed in microbial mats collected in a coastal environment of the Ebro delta. In general, cyanobacteria, diatoms and haptophyceae contribute significantly to the organic matter of these mats. Dinoflagellates are also important. Evaluation of the long-term redox status of the mats based on the sterol composition, e.g. Δ5-stenol, 5α(H)- and 5β(H)- stanol ratios, shows a good correspondence with the degree of stationary growth of purple phototrophic bacteria (as indicated by the ratio between cyclopropylnonadecanoic and n-octadec-11(Z)-enoic acids) and the relative proportion of sulphate reducing bacteria remains (iso- and anteiso-pentadecanoic acids). Comparison of the composition of these mats to that of mats developed in hypersaline environments, namely carbonate and gypsum deposition, from the same area shows that diatoms, dinoflagellate and haptophyceae inputs are also very relevant in the former. In the gypsum mats these inp...