What are my options for closing a large gap between an incisor and canine? (Photo)

The simplest option is bonding to close the gap. However, it appears that you may need to have some gum removed with a laser to make room for the bonding. It is difficult to tell from the photo. If this space and the one below have been increasing then that indicates the instability of you bite ( jaw position). A complete exam with a general dentist trained in neuromscular dentistry and who practices orthodontics would be beneficial. There is also the the option of moving your teeth with invisalign.