Lytics is capable of pulling many query string parameters out of links and this is a way to identify your email subscribers on your website when they click through an email link. Mailchimp calls this functionality a Merge Tag. Mailchimp will allow you to pass the user's unique ID in an email link. The merge tag you will want to use is:
Pulls in the $member->email->unique_id; If used in a campaign, this tag will pull in your subscriber's unique id into the campaign content and can be used to create unique links for subscribers.
To learn more about using Merge Tags with Mailchimp take a look at: