A little more information:
Spirulina was first reported as a food source for the Aztecs in the 16th century Mexico, by one of Cortés’ soldiers. It was called Tecuitlatl by the Aztecs meaning the stone’s excrement. Spirulina was found in abundance at the lake by French researcher Trait within the 1960s, but there is no reference to its use there as a daily food source after the 16th century. The first large-scale Spirulina production plant was established in the early 1970s and drew attention worldwide.
In Chad Spirulina’s history dates back as far as the 9th century Kanem Empire. It is still in daily use today, dried into cakes called “Dihe” or “Die” which are used to make broths for meals, and in addition sold in markets. The Spirulina is harvested from small lakes and ponds around Lake Chad.