The simple carbon compound present in the abiotic part of an ecosystem is carbon dioxide (CO2).

Here's why:

* Abiotic refers to non-living components of the ecosystem, such as the atmosphere, water, and rocks.

* Carbon dioxide is a gas found in the atmosphere and dissolved in water. It is a crucial component of the carbon cycle, moving between living organisms and the abiotic environment.

While other carbon compounds like methane (CH4) are present in the abiotic environment, they are typically in much smaller quantities than CO2.