Multiple separate BuddyPress Networks with multisite, but shared users

I have set up a wordpress multi-site network. I would like to be able to set up a bunch of subsites, some that have buddypress, and some that don’t. Each subnetwork would have its own content that doesn’t show up on other sites, but I'd like users to be able to join any of the sites with the same login. The problem I am running into now is that I have multiple sites set up, but it seems that buddypress is installed on them all and content posted on a subsite is posted on all the sites.

Any help at all would be appreciated.