That isn't oil burning white smoke. It dissipates too quickly. Oil smoke would hang in the air for a longer period of time.
I would pull the plugs and check them. See below for what it will look like.
If your coolant is low, I would add coolant until it is at the proper mark, then observe the coolant level after a few hours. However, when you do this, you need to make certain your ski is level 100% for the coolant level checks.
If it IS burning coolant, it will really depend on how quickly the level drops. If it only drops a little over a long period of time, then it's an early indication that some gasket somewhere is allowing it to pass into the cylinder. I'm not totally familiar with these Rotax engines yet, so I don't know if there's a path to the exhaust for the coolant to get into and burn off. However, if this were a car, I'd know for certain it is most likely a head gasket. You can get away with letting it get worse, but here's the risk you take.
In an engine with a small head gasket leak between the water passages and the cylinder, at some point that small leak could turn into a full blown head gasket failure. I've seen a few engines where the piston connecting rod in the cylinder that was leaking was bent since liquid doesn't compress. The owners of the cars all said it was slowly losing fluid over a couple thousand miles and that power was down, but they thought they could push it a little further.
When you have a head gasket leak between the water passages and a cylinder, you won't necessarily see signs of water in the oil/oil in the water (milky looking). You can pull the plugs and inspect them to see if one of them is obviously discolored. That will show you which cylinder is leaking. The plug will look like it has white ashy type deposits on it like the picture. Don't put off getting this fixed for too long.
