 Phytoplankton is used as a foodstock for the production of rotifers, which are in turn used to feed other organisms.Phytoplankton is also used to feed many varieties of aquacultured molluscs, including pearl oysters and giant clams.A 2018 study estimated the nutritional value of natural phytoplankton in terms of carbohydrate, protein and lipid across the world ocean using ocean-colour data from satellites, and found the calorific value of phytoplankton to vary considerably across different oceanic regions and between different time of the year.