IMAGING ORGANOMINERALISATION OF THE VERMELHA MICROBIAL ALGAL MAT

Evidence of microbial mats have been found in the rock record since the late Precambrian, representing one of the earliest ecosystems on Earth. Previous work on Algal mats studied their effects on the local environments and microbial contribution to mineralization. The Algal mats go through organomineralisation where the microbes mediate the layers of mineralization. The mechanism, however, is still poorly understood.

The objective of this project is to test the hypothesis that organic structures created by microbial processes induce precipitation of carbonate minerals. The algae mat was collected in Vermelha, Brazil. As the microbial algae mat decayed it began to calcify. The transitional zone between the living microbial mat and the calcified layer was chosen specifically to image the interface between organic compounds and carbonate precipitate. The hypothesis to be tested is that a visible spatial relationship occurs between carbonate precipitation and organic material, and that the organic material may be acting as a nucleation site for mineral growth. A transmission electron microscope was used because of its ability for transmitted imagery at high magnification. The TEM images presented herein show the interface between cells, amorphous organic compounds, and carbonate minerals. This research project images the interface between carbonate minerals and organic material and may help shed light on why the spatial attraction occurs and what benefits the carbonate minerals gain from using the organic material as a nucleation site.