At a lower level of biological orga

At a lower level of biological organization are concentrations or levels of specific DNA sequences, which provide taxonomic or functional information (Johnson & Martiny 2015).Various gene or intergenic sequences can be used to identify species, strains, operational taxonomic units, or exact sequence variants.For example, Miller et al.(2013) used the sequence between the phycocyanin genes cpcA and cpcB to identify cyanobacterial taxa and temporal and spatial trends in their abundance in the Yahara Lakes in southern Wisconsin. Functional genes describe the metabolic potential of a population.For example,Rinta-Kanto et al.(2005) used the mcyD gene,which codes for parts of the microcystin synthesis cluster, to distinguish toxigenic from nontoxigenic Microcystis in Lake Erie.