Metals in water question

MixedFruitBasket · Dec 25, 2019

We hear a lot in this hobby how metals such as iron are bad for corals. Which leads me to my question. If metals are bad for corals then why do they sink ships to help build coral reefs, and why do corals (even acropora) grow on those rusting bodies, steel frames, etc. I realize there is a huge water volume exchange, however, ships are pretty large and the metals have to build up in the area. Also, the corals are growing directly on it.

Just curious.

Randy Holmes-Farley · Dec 25, 2019

Who says iron is bad?

I and many, many others dose it.

that said, it is all a matter of concentration. Having enough is critical, having too much can be toxic.

MixedFruitBasket · Dec 26, 2019

Randy Holmes-Farley said:
Who says iron is bad?

I and many, many others dose it.

that said, it is all a matter of concentration. Having enough is critical, having too much can be toxic.

I'm sure there isn't just iron involved with the ships. Probably copper, definitely steel, maybe even tin...
And yes, I'd think having too much of anything would potentially be toxic. However, who/what decides the "safe" levels of those metals (or other chemicals even?)

Randy Holmes-Farley · Dec 26, 2019

MixedFruitBasket said:
I'm sure there isn't just iron involved with the ships. Probably copper, definitely steel, maybe even tin...
And yes, I'd think having too much of anything would potentially be toxic. However, who/what decides the "safe" levels of those metals (or other chemicals even?)

Who decides? each organism decides for itself. scientists can study it, but it is a complex science as trace metals take many forms in seawater, which vary in bioavailability and toxicity.

there’s really no conundrum here about the shipwrecks. Trace metals are in short supply in the ocean. Iron limits phytoplankton growth in much of the ocean, as has been proven by adding soluble iron and observing increased growth.

copper is also critical for corals. does copper or tin ever rise to toxic levels near a wreck? Maybe. But water flow is always washing it away.