Black stains on cedar deck: a salt water/metal problematic situation?

[Elcomico]

In my biannual deck sanding and staining adventure I noticed a lot of black stains on my cedar deck. I ruled out mold for obvious reasons and my internet searches have led me to believe that "metal" has gotten into the wood and is reacting to the salt. I've had metal staining issues in my fiberglass pool and I know metal is "around".

Since my other deck far from the pool and built at the same time and with the same material doesn't suffer from this affliction, the salt water looks like the likely culprit.

Has anyone else experienced this issue?

As always, many thanks!

https://www.icloud.com/sharedalbum/#B0UGI9HKKJPBtcM

 

[cowboycasey]

that is a very nice looking deck...

I would think if it were water you would have the stains on the boards closest to the pool also... looks like soda or something acidic got spilled on those spots and then maybe water got into those spots?? just thinking out loud..

I was thinking of staining like you did, does it get slick when water gets on it? I did the 10x paint and it works great but man that stuff gets smokin hot...