A month ago when I thought of microbial mats, the only image that popped into my head were the domed structures in Shark Bay, Australia… layers of living microbial communities that grow, flourish, and trap sediment. In the “Living in the Microbial World” workshop at Woods Hole, we had the opportunity to venture out to the Sippowisset marsh in Woods Hole and take samples of microbial mats. Using a scooper, we took a sample of the mat (it looked like a brownie) and put it in a plastic bag. The mat samples had definite layering to them: the top green layer had some cyanobacteria and the pink layer had some purple bacteria. We took the mats back to the lab and looked at them under a light microscope. The main challenge there was separating the bacteria from the sediments. Under the scope I could see the stringy cyanos on the top layer and the purple bacteria on the bottom layer. Brad gave us some insight as to how the bacteria in these mats metabolized sulfur and nitrogen. By sticking an oxygen electrode into the microbial mat, we found that oxygen levels changed with the depth of the electrode. They were different with each layer. We also found that when the mat was deprived of light, the microbes’ photosynthesis shut down… as did the oxygen production. As oxygen was rapidly consumed, oxygen levels dropped dramatically. In later posts I will write abou the interactinos between theese microbial communities.
