2.2. Collection of soil profile samples
Soil profile samples were collected on December 4, 2013 from a natural depression in the Al Kharrara area. This site is covered with thin biological desert crust and serves as a long term monitoring station for our research team (Richer et al., 2015). Surface soil samples were collected aseptically from three adjacent plots, followed by 5 cm vertical incremental sampling up to 25 cm depth. Soil profile samples were kept in the dark at room temperature and analyzed for BMAA, AEG and DAB as described below.
2.3. Microscopic observations of water samples
Water sub-samples were fixed using Lugol's Iodine or 20% (v/v) ethanol and were observed with a fluorescence microscope as described in Metcalf et al. (2012). Cyanobacteria were identified to order and genus levels based on taxonomic classification guidelines by Whitton (2002).