The cerium contents of several coastal water samples were found to be 0.1 to 0.6 µg/l. These are in contrast to the cerium concentrations of 0.004 and 0.014 µg/l observed in samples taken near Bermuda….
Carpenter, James H., and Virginia E. Grant. 1967. "Concentration and state of cerium in coastal waters." Journal of Marine Research 25, (3). https://elischolar.library.yale.edu/journal_of_marine_research/1101