The deal will also send prospect Matthew Bartkowski to the Bruins' organization, with Craig Weller and a second-round pick going to the Panthers.
A fan favorite in Boston for his physical play, Bitz's production left something to be desired. In 80 NHL games, Bitz has just 16 points and a minus-9 rating. He played in five playoff games last year, registering a goal and an assist.
Seidenberg, 28, had a career-high 30 points last season, and with 23 this season, he's on his way to topping that mark. He has two goals and 21 assists this year for Florida, and he'll instantly fill the void that Derek Morris left when he was traded to Phoenix earlier in the day.