In the terrestrial carbon cycle, the abiotic reservoir from which living organisms directly obtain their carbon is

The Atmosphere is the abiotic reservoir of carbon where living organisms obtain it.

Explanation:

Carbon reservoir is the large storing place of carbon where it can be obtain. We have the biotic reservoir(living or biosphere which includes soil, water) and the abiotic reservoir which is the atmosphere.

Carbon is obtained in the form of carbon dioxide from the atmosphere by living organisms which the plants use it for photosynthesis and it is a building block in animals. Carbon dioxide is 0.033% in the atmosphere.

oceans

indian ocean

pacific ocean

atlantic ocean

arctic ocean

southern ocean