What will happen to a food chain if the carbon cycle is interrupted?

Answer 1

The carbon cycle and the food chains co-exist more or less independently of each other.

The natural carbon cycle is also more or less in equilibrium - the amount of carbon absorbed being roughly the same as that which is released. If the cycle were interupted there would be little effect, certainly in the short term.

The most vulnerable area is the oceans. At the bottom of the food chain are plankton, it is phytoplankton that would be directly affected by changes in the carbon cycle - these minute organisms live near the oceans surface where they photosynthesize. Some other plankton, protozoans or metazoans, feed on phytoplankton.

If there was no carbon then phytoplankton would suffer having consequences throughout the marine food chains.

There are many other more abstract consequences of an interuption to the carbon cycle in relation to food chains but going into detail would probably not answer your question as it would involve going off at a tangent and involves much speculation.