High Performance Liquid Chromatography (HPLC) machine
Phytoplankton are the primary producers in the sea and form the base of the marine food chain. All phytoplankton have the pigment Chlorophyll a, just as land plants do. But phytoplankton also have "accessory" pigments which gives them slightly different coloration. These accessory pigments can be measured using a High Performance Liquid Chromatography (HPLC) machine. This machine separates the pigments from a water sample and gives a relative measure of the groups of plants that are present in the water. This is much easier than counting each individual phytoplankton cell!