Systems and methods for serving dynamic content (such as advertisements) in response to dynamic content requests are presented. More particularly, systems and methods for serving dynamic content from dynamic content portfolios directed to trending events and/or topics are presented. Upon receiving a dynamic content request, content classifications corresponding to the requested, published content (i.e., the requested content) that included reserved dynamic content space which initiated the dynamic content request are determined. A current trend is identified in a content classification when the dynamic content request volume for the current trend period exceeds the standard/expected dynamic content request volume for the current trend period by at least a threshold amount. When a trend is detected, candidate content portfolios directed to the trending content classification are selected from a set trending content portfolios. A content creative is selected from the candidate content portfolios and returned to the requesting computer user.