Presentation by Dr. Jonathan J. Cole, Cary Institute of Ecosystem Studies Starting in its earliest development, limnology has tended to view lakes as rather isolated from their terrestrial watersheds. This view of lakes as microcosms (Forbes 1887) proved useful in some ways, but it failed to help explain phenomena such as eutrophication which is driven by the external input of nutrients. While the study of limiting nutrients has fully embraced the watershed for decades, the study of C cycling in lakes has maintained a somewhat microcosm viewpoint. This is a viewpoint in which organic C is envisioned as being formed almost entirely by photosynthesis within the system (autochthonous sources); exogenous sources are largely ignored, downplayed, or assumed to be refractory. A number of disparate research threads in recent decades have completely overturned this view.