PHYS1160 Lecture Notes - Lecture 3: John Wiley & Sons, Hamelin Bay, Western Australia, Stromatolite
Document Summary
Stromatolites (cid:894)(cid:862)ro(cid:272)k (cid:271)eds(cid:863)(cid:895) is defined as layers of accumulated, organo-sedimentary structures created when sediment is trapped, bound and cemented by biofilms or algal mats of microorganisms [1, 2]. They appear in a wide variety of shapes (flat, domes, cones, columns) and sizes with alternating light and dark layers [3]. For some aussie pride, the most notable example of living stromatolites is in western australia [figure 1]. Figure 1: stromatolites in hamelin bay, western australia [3] Originally, there were formed from layers of photosynthetic cyanobacteria, a blue-green prokaryotic microbe. During bacterial photosynthesis, the depletion of carbon dioxide (co2) in the surrounding water results in the precipitation of calcium carbonate (caco3). This precipitate, and sedimentary grains, become trapped in the adhesive layer of biofilm formed by the bacterial colonies [4]. This thick biofilm is created to protect cyanobacteria from uv radiation and desiccation [7]. As the bacteria is photosynthetic, it will move upward through the sediment layers until it reaches light.
