Head wood "spalt" in the counter

It is wood "spalt" in the pictures.

"That looks like "spalt" to me, which is another word for a fungus. In some woodworking circles, spalt is a good thing, but not when it impacts the wood's shape. It looks to me like you have some kind of water leak in that region that is helping to feed the fungus. I'd suggest looking for the source of the water first. You can sand back the edge and judiciously apply bleach or a fungicide (technically, bleach isn't FDA approved for use as a fungicide or a mold killer, if I recall correctly). When you have it all dried out, consider sealing the area with epoxy."

We started noticing it when we varnished the Oak about a year ago. It was just a small black spot and we thought it was from water. It has spread and now we noticed that the door (laundry hamper) sticks. We took a close look and think it is some living unwanted something.

"That's the issue with using Red Oak in a marine environment. Stripping it and bleaching with Oxalic acid should bring it back.

You do realize you are getting fresh water incursion from somewhere to get that right? Find and fix your leaks..."

The good news is we have a solution to kill it.
No need to remove wood. We will strip the varnish and kill, kill!

There really is no bad news here as we were planning to replace the sink and faucet soon. We are almost finished with our refer build and that project was next.

 We will look for a water leak and it should not be hard to spot. That sink area is very is easy to see about and not much plumbing.
 We have not noticed any water in our “laundry hamper” under the sink. It could be from water on the counter from the tiny sink. It tends to splash about some. We have a towel for wiping up around the sink after washing hands etc.
We will look really good for a water leak(s)!