A Cyanobacterial filament finds itself struggling to get enough light energy to continue growth. What is the likely outcome of this situation?

It will result in akinete formation.

Explanation:

A thick-walled, non-motile, enveloped, and dormant cell produced by filamentous, and heterocyst producing cyanobacteria is known as an akinite. The formation or development of Akinite generally takes place at the time of the stationary phase and is instigated by unfavorable conditions like less amount or inadequate concentration of nutrients or light, levels of salinity, and temperature of the surroundings.  

Therefore, it can be stated that at the time of experiencing reduced or lessened concentration of light by the cyanobacteria, it will begin the formation or development of akinite.