Have you tried the Google?Spirulina search on Google
It has lots of information.
as far as nutrition, calorieking.com has pretty much anything you can eat on it.
1 cup dried (1/2 oz)
1.2 g Fat
3.6 g Carb
8.6 g protein
so 1 cup dried powder has about the same protein as 1 cup of milk or 1/5 cup uncooked black beans. but i would highly discourage eating 1 cup of dry powder.
It is proportionally high in protein (about 50-70% of calories) but i don't think it could realistically be a significant
source of protein in your diet.
It is full of other nutrients, and is great for you. But i suggest you look elsewhere for the major sources of your protein.