A photosynthetic prokaryote contains chlorophyll a, may form blooms in polluted water and sometimes possesses specialise
Cyanobacteria are photosynthetic prokaryotes containing chlorophyll a. Their colonies may form blooms in polluted water, and some members fix atmospheric nitrogen in heterocysts.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Protista - Chrysophytes and Dinoflagellates