excerpt on gbooks:
http://books.google.com/books?id=N1DTZ18N-_YC&lpg=PA1&pg=PT1...
also, remember cyanobacteria was one of the first organisms to turn the sun for its energy. here is excerpt from Home documentary by Yann Arthus-Bertrand, that mentions cyanobacteria:
http://youtu.be/jqxENMKaeCU?t=5m47s
hope this helps.
However it can't be the only thing you eat. There were some studies about using spirulina on a spacecraft (or sub) for both 100% of oxygen and food. While it was feasible, it was pretty energy intensive and would tend to kill you after a few months. Something about more protein in the blood than your kidneys could filter? Will try to find a link.
maybe it was the sodium?
edit: wanted to add/clarify that some days i only took half of what i planned..was not hungry. my friend said i need to eat 3000 kcals of it..i said no, as i'm just going to get an athletes dose of it. the bet was to show you could function normal with averages+ doses.
also don't drink it/ add the spirulina powder to a smoothie..the taste is very acquired...its not terrible but easier to swallow tablets.