Some background:
- Based on Django
- User submitted content
- I'm in the USA (NYC to be exact)
Any other relevant information you need to make a suggestion, just ask in comments.
From Related question
You automatically have the copyright to any work you create. There isn't an official register of copyright. You can apply for trademarks and patents if you have anything that qualifies.
Based on that answer I'd say it is unnecessary for your own content. As for the user submitted content it gets sticky. What if someone has posted copyrighted content of their own or from another source? You cannot claim copyright on it yourself as it has already been copyrighted by someone else. If you want to copyright the original content of user submitted content you will need to make sure your terms of service state that any original content posted by your users is copyright by you and make sure they have to agree to those terms before submitting content so they cannot claim ignorance if you do use their content for your own purposes.