Assistance to ID what substance is floating on top of the water

Hi first post. IG vinyl 40x20 pool in Northeast, pool open for about 3 weeks. Water levels look good (pH 7.2, Alkalinity 100, free Chlorine 2-3), water looks clear in general except about a week ago started getting strange small film all over the top of the water. See pic ( http://s33.postimg.org/6yamvahbj/image1_1.jpg ) ...a little hard to see but should be able to spot.

At first I thought pollen-we have lots of trees and flowering plants....not no color to it and they don't clump. Almost looks like soap scum you would see in a bathtub.....if I dip a finger in the water the material seems to repel away. Stays in small little clumps and really hard to skim. The only thing I added beyond shock to open this year was a iron stain removal granule for the vinyl iron stains. Any thought/ideas what the material is and what might be causing it would be appreciated!

Thx
Jeff