Toxic Seaweed is an Atlantis Environment that says:
“Whenever a hero uses a power, this card deals that hero 3 Toxic Damage.
At the end of the environment turn, 1 player may discard their hand to destroy this card.”
Can a player with no cards in his/her hand discard his hand of 0 cards to cancel this environment?
Respectfully, I disagree. If the card listed a number of cards (such as: "1 player must discard 1 card to destroy this card"), then yes, you would have to discard that number of cards. However, if a card says to discard your hand, well, you can discard a hand of zero cards in order to fulfill that requirement. As a player, you always have a hand, even if you happen to have zero cards in hand.
The only time that this is not true is when your hero is Incapacitated. At that point, you've removed all of your cards from the game and no longer have a hand, unfortunately.
But, I always have two hands, whether I'm playing the game or not. (Although, I can't really be sure I will always continue to have two hands in the future.)
He also said that, if I'm willing to discard one of those literal hands, then he'd rule I could destroy Toxic Seaweed. Although, I could only do that twice in a life time.