You need to place the args to the -e switch in quotes. So, you should have:
rsync -rdtvu --delete -e "ssh -p 22 -i /path/to/sshkey" /media/local/media/ email@example.com:/media/remote/dir/
To make this easier for the future, you man want to add something to your ~/.ssh/config file. For example:
Of course, port 22 is the default so you don't need to add that unless you use a non-standard port.