A paper chromatographic method was used to separate chlorophylls from carotenoids in marine phytoplankton from seawater and benthic samples. In seawater, chlorophylls a and c and the carotenoids fucoxanthin and carotene were always present. Chlorophyll b was a major pigment on the two occasions when blooms of a green euglenoid organism were abundant. The two main types of degradation products found in the plankton were chlorophyllides and pheophytins.