New pond,1/4 acre, 8’ deep, western N.Y

Just put this pond in in September. Filled completely in 3 weeks. I’ve already got fil. algea in one area, a patch about 4’ in diameter showed up about 2 weeks ago. The area where it is is the last place to freeze over, if that makes any difference . I wasn’t there for all of the construction but remember my contractor said water came gushing out in that spot when he excavated it.
I was hoping to see some weed growth by spring , before I stock, but really wasn’t expecting this. Do I have an issue here?