Being your neighbor (Alabama), I'm experiencing the same thing in my pool with a similar wooded setting. One way to tell if its pollen or not is to get a fairly constant wind direction for a day or so and the pollen will "pile" as it settles on the liner on the downwind side. It is notorious for settling down the sides of my pool. I have to run my pool cleaner and keep the water "stirred" so that the pollen will remain suspended in the water long enough to be filtered out by the sand filter. The DE trick helps as well.