Algae stencils for a giant chalk wall developed as part of the MOXI Museum exhibit highlight phytoplankton as chalk, also known as calcium carbonate. Chalk is a very pure biogenic fine-grained limestone made up of marine dandruff, the hard bits of marine algae (coccolithophores) that have settled to the sea bed.
If large algae blooms occur, the chalk-laden, green/white water can be seen by satellite. Paul Matson, a UCSB postdoctoral scientist, counted 5 million coccolithophore cells in just one liter of seawater during a Santa Barbara algae bloom in 2015. – Michael Stout, Santa Barbara Independent News, 2015