Small amounts of titanium have been detected in sea water by a colorimetric procedure using a thymol reagent and also by a spectrographic method. Diatoms and sea muds were found to have larger amounts of titanium than sea water. Thus it would seem that titanium is concentrated by diatoms in their shell structures.
Griel, John V., and Rex J. Robinson. 1952. "Titanium in the sea." Journal of Marine Research 11, (2). https://elischolar.library.yale.edu/journal_of_marine_research/768