Light micrograph of red algae Polysiphonia sp. This photograph shows the top branches of the algae colony. Polysiphonia species are entirely marine, found growing on rock, other algae, mussels, etc. Red algae possess pigments of the phycoerythrine (red) and Phycocyanine (blue) group, involved in photosynthesis. Phycoerythrine reflects red light; hence the perception of the red colour for us. The pigment absorbs rays in the blue-green-yellow range of the spectrum. These colours can penetrate deeper in the seawater than rays of other colours, and that is an advantage for the red algae. Magnification: x325 when printed at 10 centimetres wide at its longest edge.