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Plan language summary: Elements (including barium and magnesium) measured inside microscopic fossil shells are higher than expected and could reflect contamination or could reflect key information about the ancient surface ocean. For example, barium may reflect how much organic carbon is produced in the surface ocean, some of which is sunk to the deep ocean and thus removed from exchange with the atmosphere, effecting climate. Previous studies have attributed higher concentrations of these elements to contamination that forms on shells and have established harsh chemical cleaning techniques to remove the contamination. However, these cleaning techniques also remove parts of the shell that contain key information about past ocean conditions. We determine that high concentrations of these elements are not due to contamination in our samples and likely reflect conditions of the surface ocean. In future work, we suggest using techniques that measure at the microscale to confirm that there is no contamination and we suggest using more careful cleaning that preserves these elements. Preserving these elements in fossil shells may provide key information about organic carbon production and cycling in the surface ocean, which is critical to reconstruct carbon exchange between the atmosphere and ocean.