BERLIN (AP) — Mainz defender
Schalke had two good chances in the opening minutes, with Loris Karius producing fine saves to deny Klaas Jan Huntelaar and then Joel Matip from close range.
The visitors had six efforts on goal in the first 20 minutes, only for Bell to score after a corner in the 28th and make it 2-0 with a header from another corner three minutes later.
The home side moved eighth, five points behind fifth-place Schalke.
"The target was to stay in the league," Mainz coach Martin Schmidt said. "The next few weeks will be a little easier now."
Schalke is being challenged by a number of clubs fighting for Europa League qualification, with the rest of the 30th round still to be played.