Generally bloggers tend to face such issue because people are using bad way to get links rather than earning it. Anyway there are tons of ways you can block spam from your sites. One of the most commonly used method is to use plugin. I am assuming that you are using the latest WordPress version so you use any WordPress anti spam plugin from the following list:

Akismet Anti-Spam
Anti-Spam Bee Plugin
Spam protection, AntiSpam, FireWall, Cleaner by CleanTalk
Spam Master
Anti-spam
Cookies for Comments

Above mentioned plugins are free and easy to use if you are facing any security issue then I would recommend to use WordFence and 2 factor authentication plugin. All the best