The protein rich alga is :

Chlorella, commonly known as space alga is a protein rich alga, containing about $50 \%$ protein, $20 \%$ lipids, $20 \%$ carbohydrates and a little percentage of vitamin- $\mathrm{B}_2, \mathrm{~B}_{12}, \mathrm{C}, \mathrm{H}, \mathrm{K}$ etc.