Merlier wins crash-marred opening stage of UAE Tour
The finale was marred by a high-speed fall with around 20 riders hitting the tarmac hard and three-quarters of the peloton caught behind it.
The fall was caused by a shoulder barge with some riders taken away by ambulance.
Merlier had predicted a fight for the opening stage due to the quality of the field.
"It's my first win of the season so I'm very happy," said the 31-year-old who has previously won stages at the Giro d'Italia and the Tour de France.
"I made the decision to ride round from the side because I was blocked. I saw (Fernando) Gaviria (Team UAE) go. I could see the finish line so I went for it," said the broadly smiling Belgian at the finish line.
Contrary to the weather forecast, there were no cross winds in the finale and very little sand on the road during the 141km opening run through the dunes.
Of the field of top sprinters at the seven-stage event, which includes four flat stages, two climbs and one time trial, British veteran Mark Cavendish and Dutch fast-man Dylan Groenewegen were caught behind the fall while Elia Viviani fell hard.
Tuesday's stage is a 12.1km individual time trial raced on an atypical route featuring almost no turns.
Merlier will be the last man down the ramp while Spanish rider Pello Bilbao will be the last of the contenders for the overall title to come down the ramp after he won time in the mid-race intermediary sprint.
Neither 2023 champion Remco Evenepoel nor Team UAE's superstar Tadej Pogacar are competing in this sixth edition, leaving Pogacar's teammate Adam Yates favourite for the title.