I am making a lager beer, and have used Wyeast 2278 Pilsner yeast. I pitched 2 packs (100bn cells per pack, viability 70% as per the Beersmith cals) into my wort, and have defnitely noticed yeast growth activity. After a few days of fermentation (7.5deg C or 46deg F) I am getting the traditional "foaming" on the top of my wort and CO2 emmission through my airlock. However, under the surface of my wort (but near the top of the wort) I have seen evidence of a sponge-like growth (really quite large) which I have not seen before in previous batches. Does anyone know if this is normal or expected? Will it interfere with my beer, or will it eventually drop down and form part of the yeast cake ?