If you’ve linked your Google+ to your Blogger account, Google now automatically shares new blog posts publicly on its social network as soon as the post is published without additional clicks. Google justifies this new integration not only to save you time but also to help get the conversation going and expand your blog's audience and engagement by automatically resharing your content. If you want to opt out of the feature, you can change your preferences in the Google+ tab on your Blogger Dashboard.
Source: Blogger Buzz