Slime mold can appear in either white, yellow, orange or black, and normally referred to as dog vomit mold when any color but black. There's just something sinister about how it just shows up in the morning when it's black in color and doesn't get mistaken for the result of a sick animal. A perfect case study regarding black slime mold on engineered wood fiber in a playground follows:

It can seemingly appear overnight in a black square foot patch of slime mold on the playground EWF, which changes shape and size over time if not removed. The problem was, this was happening every morning within this community playground. Their solution was for the landscaper to show up very early every morning to locate and remove the daily black slime mold patch(es) before any residents or their kids showed up to play, and sometimes there were spots, plural.

What was discovered was 3" of EWF at the top was fairly recently added, but the playground had never been properly prepared, or properly installed to begin with, nor had it been properly inspected and maintained, for many years. Hiding underneath was roughly a 4" depth of fine powdery EWF that had broken down and was channeling up moisture from about 5" thickness of black sand under that, similar to a light tar and smelling of sulfur. The playground sand had never been fully removed before moving to wood products, never a good idea. Everything turned into a microbial soup, starting with improper drainage, then add the animal waste that had been within the sand that wasn't removed, throw on some wood products that don't get properly maintained, breaking down as wood products always do, and it cooks into a nasty soup. Then add the perfect top layer for slime mold to pop up through, a thin layer of fresh EWF. 

It all had to come out and get completely cleaned out, so it was now 12" lower than the surface needed to be when done, relative to the elevation of installed playgound equipment not being replaced. The 12" depth is standard for sand or wood products, you just can't add them together. They used the sub-base recommended, installed it properly with drainage, then installed 6" thickness of rubber mulch, and the daily nightmares are over.