Many water storage tanks have as part of their design a partially covered hole near the top lid, which serves as an overflow control. Exchange of air and dust particles as well as light penetration occurs through that hole allowing for recruitment of atmospheric microbes attached to particulates and for photosynthesis to take place. Nitrogen fixation and carbon dioxide fixation through photosynthesis, allow metabolic independence and enable cyanobacteria to be potent eco-strategists and pioneer species in otherwise nutrient-limited water bodies and dryland soil surfaces (Powell et al., 2015). In the absence of growth controls exerted on cyanobacteria through e.g. Mo bioavailability, light and nutrients, and the lack of disturbance by water-mixing, cyanobacteria can attach to the internal walls of water tanks and proliferate. Our finding that AEG correlates significantly with tank exposure to the sun may then be explained by the increased activity of cyanobacterial-toxin-producers found in these water impoundments (Table 2). Finally, as the cyanotoxins BMAA, AEG and DAB are persistent on surface desert crusts and as deep as 25 cm in the soil horizon, a bioaccumulation potential exists if they are leached into groundwater (Table 3 and Table 4; Richer et al., 2015).