An 11th consecutive home win for Marcelo Bielsa's men was sealed four minutes after the break, when Dimitri Payet was fouled in the box by Cedric Barbosa, allowing France international Andre-Pierre Gignac to duly dispatch the resulting spot-kick.
The hosts could have added a second late on, but Payet's vicious volley was denied by the crossbar.
The result sees Marseille go level on points with Paris Saint-Germain, one behind leaders Lyon.
Elsewhere, Montpellier's hopes of securing a UEFA Champions League spot were handed a setback as they were held to a 0-0 draw at Lorient.
Despite extending their unbeaten run in the league to seven games, Rolland Courbis' men are now 11 points off the top three and face a real fight if they are to seal a place in Europe's premier club competion.
The only other game to end goalless was Nice's trip to bottom-of-the-table Metz, which was played under difficult snowy conditions that saw most of the pitch markings having to be redefined at half-time.
The visitors were reduced to 10 men late on when substitute Neal Maupay was dismissed for a push on Sylvain Marchal, but the hosts could not take advantage on yet another frustrating outing.
A miserable season shows no sign of getting any easier for Metz, whose winless run in the league now stretches to 11 games, leaving them firm favourites to make a swift return to the second tier.
Elsewhere at the bottom, an Aleksandar Pesic goal ensured Toulouse eased their relegation concerns with a 1-0 win at home to Reims, while also halting a winless run of seven games in all competitions.
In the day's other two games, Lille avoided a third successive Ligue 1 defeat with a 1-1 draw at Nantes.
Jonathan Delaplace gave the visitors the lead after 14 minutes, before Oswaldo Vizcarrondo popped up to rescue a point 10 minutes from time.
It also finished a goal apiece in the game between Lens and Bastia, with second-half spot-kicks from Ryad Boudebouz and Ahmed Kantari ensuring a share of the spoils.
