Why and for Whom do we clap?

An incredible video snippet from David Gallo's TED talk "underwater astonishments", one of the top 10 most viewed TED talks of all time.

A simple question: Why did it end in spontaneous applause?  For Whom were these people clapping?  The octopus?  Gallo?  I think not.  Then for Whom? SomeOne else.

Romans 1.20.