mould on wood window stool close to sink

[LLL]

My window stool has mould and has become black on the top and also on the part connecting with the kitchen worktop. I know it is because of the water splashing on it constantly.  Can anyone suggest how to recover and use anything to protect for the future (painting?)? 

 

Also, I can see there is a big gap between the stool and the worktop. I believe I should fill it; otherwise, water will keep pouring inside since you can see the kitchen sink is there. Any suggestions, please? I am not sure that is because the sink of the worktop or the wood is bent up. It looks due to the sink of the worktop. 

thanks 

 

 

[Beau]

Oxalic acid should help remove the mould marks.

 

Any varnish or wood oil should help protect agains it happening again. 

 

That looks a fair sized gap and it's hard to say what the cause is. The worktop shouldn't be able to drop presuming its well secured to the wall underneath and the base units are tight up against it. If water is running in the gap and wetting the underside of cill that will cause the lower side of the cill to expand while the top is not getting wet to the same extent this would cause the cill to 'cup' upwards.