This Zotero Group explores the relationships, patterns and roles of mutualistic symbioses in creating, structuring and facilitating both naturally present and human-modified ecosystems of the Potomac River Valley -- on land, in the water and through the air. The site is a product of a semester-long seminar course developed in Spring 2010 by a dozen graduate students and an alumnus (now professor) of Environmental Science and Policy at George Mason University in Fairfax, Virginia.