This is algae, or mold, plus calcium deposits from the water in the taps that sits, and due to humidity, darkness and opportunity grows this black mold.
You should always dry around your basin and bath taps.
Secondly there are sprays and cleaners with mold killer in them which can eliminate this problem.
If you already have mold in your shower, tiles and taps. Buy some mold spray and a mask and gloves.
Give all surfaces a good wetting with it, and then leave it to soak in for an hour or so, then return with the mask on and gloves, and give the whole bathroom a good scrub. Then repeat with a bathroom cleaner like vim, and rinse it all off, you should do this once a month in a damp, dark bathroom, as it will grow again.
You should always dry around your basin and bath taps.
Secondly there are sprays and cleaners with mold killer in them which can eliminate this problem.
If you already have mold in your shower, tiles and taps. Buy some mold spray and a mask and gloves.
Give all surfaces a good wetting with it, and then leave it to soak in for an hour or so, then return with the mask on and gloves, and give the whole bathroom a good scrub. Then repeat with a bathroom cleaner like vim, and rinse it all off, you should do this once a month in a damp, dark bathroom, as it will grow again.