Are online classes causing summer enrollment on college campuses to shrink?

Elizabeth Donald:

Carbondale campus of Southern Illinois University saw fewer summer students this year, while the Edwardsville campus saw a slight increase — and school officials are saying online classes had an impact on both.
 
 On-campus summer enrollment at SIUC dropped 14.2 percent this year, or 571 fewer students than last. This is 1,334 fewer students than who were enrolled in summer 2014.
 
 However, when online classes are factored in, the summer enrollment at SIUC is down 5.1 percent — still a drop, but not as significant. In fact, online class enrollment grew by 8.5 percent this year.