If brown algae contain chlorophyll why are they brown and no

If brown algae contain chlorophyll, why are they brown and not green?

Solution

All the different classes of algae contain chlorophyll. However, chlorophyll pigments are of different types. All algae contain the pigment chlorophyll a but it is not the only chlorophyll pigment.

Brown algae contain the pigments chlorophyll a, chlorophyll c and fucoxanthin of which fucoxanthin contributes to the brownish colour of the algae as opposed to being only green due to the chlorophyll present. Brown algae have carotenoids fucoxanthin and violaxanthin. These abundant pigments reflect give the algae a dominant color hiding the smaller amount of green reflected from chlorophyll. These secondary pigments collect sunlight in an outer array and pass the energy to the photo system II reaction center with the chlorophyll a and the oxygen-evolving complex.