There's no XP award listed for the collapsing walkway going into Kraken's Cove. I know it's not technically a trap, but it was a "test" of sorts. Was XP left out by accident or should there not be any? I'm guessing with the Slippery Eel getting loose it's about a CR3?
I would gauge it depending upon how it played out for your group. If it was a real test, then by all means award them a CR 3. If it was laughably easy, award them half of the CR 3 or even as little as nothing at all. If it was a true task ... ad nauseam.
I generally award XP at the end of the session rather than after each encounter, dependant upon how much game time passes during the session, and never more often than once per day of game time that passes. As the session progresses I make notes as they progress, modifying the baseline CR as necessary for the 'actual' difficulty of a given encounter as they conclude a particular encounter.