Question

Explain the actions that were occurring at the cellular level to produce this movement. include sources of energy and any possible effect of muscle fatigue.

Answer 1

The only possibility when mussel didn't have power to carry our weight.

Answer 2

The possible effect of muscle fatigue is being experienced when muscles are unable to generate force.

This occurs when muscle ATP is being in the process of metabolism of biomolecules. For example sugar and fats.
ATP generates muscle contraction. Muscle fatigue occurs when ATP is being depleted and results in strenuous exercise.
There is also lactic acid accumulation and oxygen depletion.