A clumsy foul from Lewis Dunk on Callum Wilson inside the box allowed substitute Kermorgant to give the Cherries the lead for the third time, and they hung on to record a fifth consecutive league success.
Experienced goalkeeper Ali Al Habsi was making his debut for the visitors after joining on loan from Wigan Athletic, and he made a strong save at his near post after Matt Richie had exchanged passes with Andrew Surman to set up a shooting chance.
Artur Boruc at the other end was completely untested in the early stages as Joao Teixeira passed up several shooting opportunities, with a deflected Gary Gardner free kick the closest that Brighton came before the opening goal.
Albion were level within four minutes, though, as Liverpool loanee Teixeira slipped an inch-perfect pass through for Colunga to round Boruc and slot into the empty net for his first Brighton goal.
Bournemouth regained the lead seven minutes prior to the break when a cross was allowed to travel to Marc Pugh at the back post, and the midfielder smartly volleyed the bouncing ball into the bottom corner via a slight deflection.
Dunk turned out to be the villain for the visitors, but had so nearly been the hero at the start of the second half when his header bound for the bottom corner was parried around the post by Boruc.
When following his strike partner Colunga in opening his Seagulls account, Baldock showed no such hesitation as he drilled emphatically left footed into the net after latching onto Gardner's flick on.
Gardner then wasted a good chance to put Albion ahead when he blazed over at the back post after good work from Kazenga LuaLua, and Bournemouth soon went up the other end to make him pay.
The otherwise-quiet Wilson was clattered from behind by Dunk on 76 minutes, and Kermorgant sent Al Habsi the wrong way from the spot to set up a victory which sees the Cherries climb five places in the table.
Craig Mackail-Smith's near-post flick was the closest that Brighton came to levelling again, but Hyypia's charges could not muster a third response and remain one place above the relegation zone after a slender loss.