What is it called when an organism signals another that their interaction is not serious or threatening? cooperation metacommunication agonistic interaction courtship?

The answer is metacommunication. Utilizes cues that are interpreted by the individuals of a population into useful information.  Kinesics, referring to body motion communication, is also a part of metacommunication. It also applied to humans where posture, gesture, stance, and movement are also interpreted as cues  in communication.

explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.