Thought I would give an update on my bubbling situation. It has been 4 years now...still have the same areas of bubbles in the deep end of my 2-acre pond! We now think they're due to air/water escaping the limestone beneath the pond. There has never been any seepage/leaking and the water level doesn't drop drastically during dry spells. Water temp around the bubbling areas is colder than other areas. Those areas don't freeze over in the winter. BTW I didn't take Trialsguy's advice but was tempted. I love science experiments...
