Photos of Knize with the enormous fish — including one of him pushing it across North Avenue in a shopping cart — lit up Twitter last week, bringing back memories of Chicago’s favorite wayward alligator. But unlike Chance the Snapper, who experts quickly determined was an illegal pet released into the pond, Knize’s catch raises environmental questions: How did an enormous carp — an invasive species — get into the manmade lagoon? And what does its presence mean for the urban pond and vulnerable Lake Michigan? While Knize waits to see if his record is verified, state environmental officials plan to visit the lagoon this week to ensure the colossal carp is the aberration they suspect it is and not a sign of trouble for local waterways.