Meme posts outside of meme communities

I've noticed this happening more and more lately, that joke/meme posts have gotten posted in communities meant for more serious posts. Since there are a number of communities meant for meme posts and other less serious content, it would be better for these posts to be made in those communities. Is there anything that moderators can do about this? Given how I've seen these things go in the past, I'm a bit concerned that the communities for serious discussion could end up as just another place for memes, which would be a detriment to Lemmygrad as a whole.