Pollen is not stopped by your Looplock cover, it just passes through. If that is your only reason to keep the pool covered, open it. The key determenent on a mesh cover is water temp, when the water gets above ~50 deg., algae can, and will, start growing. The easiest way to deal with algae is to not let it get a foothold in the pool in the first place.
Pollen can easily be filtered out via the skimmer(s), it floats on top of the water. In contrast, algae can be a real "female dog" to get out of the pool. I believe that you are better off opening and maintaning the pool a couple more weeks, than fighting algae for the first week you're open (and backwashing, dumping in chems, vacuuming and readjusting chems) - in the long haul, you should save $$. ( But that's just my $.02 )