What caused my huge drop in search ranking?

[bioworld]

On February 8th, 2012 my site's non-branded search traffic dropped overnight by over 80%. It appears I've been hit by a Google penalty.

I submitted a reconsideration request and one of Google's staff replied letting me know it was NOT a manual penalty. So it's clearly a result of an algorithm.

What is the cause? I haven't made significant changes to the website in the previous months do to being out of the country and the holidays. I'm extremely careful not to out source SEO so there is no chance of questionable link building strategies, unless my competitor launched an attack on my site.

I've considered these possible causes:

• Duplicate content - My site had some redundancy from a marketing plan before Google Panda launched. Last month, I removed all duplicate content.
• Unnatural link building - I've been moving slowly my site, page by page, from adbio.com to bioworldusa.com after a brand change. Perhaps the 301 redirects triggered a flag in Google's algorithm. I've since removed all redirects to see if that will fix the issue.
• Poor User Experience - I recently upgraded my Drupal CMS and had to change themes. Currently my theme is an ugly, grey theme which may cause a higher than usual bounce rate. I've been trying to compensate by making sure the content is high quality.

The penalty affected these website:

• www.bioworldusa.com (2/8/12)
• blog.bioworldusa.com (2/8/12)
• www.adbio.com (2/17/12)

[TheGrid]

Are you comparing adbio.com to www.bioworldusa.com when you are calculating rankings drop or are you saying traffic to www.bioworldusa.com has dropped?

[Boodreaux]

I gave question a thumbs up.  Sounds scary.  I am looking forward to an answer too.  I will have to look up branded and non-branded but I also had 43 terms go down on me this past week.

[TheGrid]

On first glance I would blame this on the domain migration.

[bioworld]

The domain transfer happened over the last 2 years.

I would transfer a few pages using 301 redirect, wait a few months and track the outcome in ranking.

Before Feb 2012 this was working great. The last major redirect happened on Jul 28, 2011 when I redirected the homepage.

I recently started the Blog on Dec 19th, 2011 by moving irrelevant content that was originally on adbio.com and partially moved to bioworldusa.com. My hunch is the blog got hit by Panda updates for being low-quality. But I thought the Panda update treated sub-domains differently.

[jenadams]

Same here

[bioworld]

I've reversed the domain migration and am waiting for results. Already the old site is starting to gain ranking after 3 days.

How should I go about migrating this content in the future?