Microbial communities in the water column of the ferruginous meromictic Lake La Cruz (Spain)

Ferruginous meromictic lakes are considered potential modern analogues of an ancient anoxic, iron-rich Archaean Ocean. We determined microbial community structures in the water column of Lake La Cruz (Spain) using 16S amplicon sequencing. Microbial community structures were related to detailed physical, chemical and isotope data, as well as rate measurements of key biogeochemical processes (methane oxidation rates, N2O transformation rates). The two step library preparation protocol was done using 18 PCR cycles in the first PCR, and for comparison with 25 PCR cycles, to evaluate the effect of the number of amplification cycles on the obtained community structure data and corresponding diversity measures.