Heavy metals accumulate in organs inside your body. Algae and other plants have a mechanism that prevents oxidative metals from damaging them. Does this mean if you eat those plants, they’ll do the same for you? It seems incredibly unlikely since the first thing your body does to these plants is digest them. You are not a plant.
Or it could be that I’ve mistaken Spirulina for Chlorella.
Because they bind with metals it’s important to get them from clean sources as I mentioned.