Regarding strontium in seawater. Strontium to Calcium ratios in fish otoliths is one way that biologists can infer migration timing of anadromous fish from rivers to the sea because the sea water is enriched with strontium relative to rivers. (anadromous fish lay eggs in rivers and the juveniles live for some time in the river before entering the sea). Elements present in the water are incorporated into bony structures relative to ambient concentrations so there is a distinct mark when a fish migrates from the river to the sea. Beyond that, strontium exists in rivers to varying degrees because of geology and you can infer from the amount of strontium relative to other elements from what river a fish caught at sea was hatched. This is useful to biologists when fish of a given species born from say St. Johns River Florida and the James River, Virginia etc... are mixing with fish of the same species from the Hudson, Connecticut, and so on in the ocean and they are subject to harvest together in the open ocean. It helps managers figure out which stocks are getting harvested the most. Beyond that utility, I'm just emphasizing in this thread that those elements occur in nature and are well known to scientists of multiple disciplines to the extent that biologists use the concentrations of various elements and their isotopes as natural "tags" of fish when funding is sufficient to screen for such. Chemtrail fanatics haven't demonstrated samples that exceed known concentrations.