This is some sort of slime mold. These are often associated with organic materials like freshly applied bark dust. Slime molds are non-parasitic fungi that feed on organic debris, so they are not unusual to see where a large quantity is placed. They tend to disappear as quickly as they appear and do not require control. Te link below is to a discussion of slime molds on lawns, where they appear different but are not considered a serious problem. Feel free to write with further questions.

https://pnwhandbooks.org/plantdisease/host-disease/lawn-turf-slime-molds