... Over time, it may simply evaporate and/or dissipate. I would think that, over time, the wind will blow it towards the edges of the pond where it will collect and simply break down. Sunlight (which has Ultra-violet rays) should speed up the process.
However, if it's like an 'oil spill', I wouldn't know what to do about it. For now, don't stock the pond with fish or anything until you don't see the slick for a while.
Other than that, my best to ya and hope this helps.