Dissolved organic carbon (DOC) in aquatic systems derives from two distinct sources; either autochthonous primary production within the system or from allochthonous organic carbon entering the system from the catchment. Allochthonous DOC is one of the largest organic carbon fluxes from catchments to aquatic systems (Hinton et al.1997,1998). Allochthonous DOC through its effects on microbial processes, plays an important role in driving metabolism, decomposition and food web dynamics at the ecosystem scale. Interestingly, the importance of allochthonous DOC in aquatic systems is debated in the literature. Models of aquatic ecosystem function such as the Riverine Continuum Concept (Vannote et al. 1980) and the Riverine Productivity Model (Thorp and Delong 1994) generally do not consider allochthonous sources of carbon as very important to the productivity of lowland rivers. The early work of Cole and co-authors (Cole et al.2002, 2006) in lakes suggested that inputs of terrestrial DOC are often biologically recalcitrant, contributing little to the productivity of higher trophic levels relative to autochthonous carbon sources. Alternatively, other theories such as the Flood Pulse Concept (FPC) of Junket al.(1989)suggest that the movement of terrestrial resources from the floodplain and catchments during flooding and rainfall events may be a significant source of energy to aquatic systems. More recently,paradigms about autochthonous carbon dominating lakes are being questioned (Cole et al. 2011). The significance of allochthonous DOC to aquatic ecosystems is being further recognised with the understanding that terrestrial subsidies are playing a much greater role in some systems than previously thought (Tanentzap et al. 2014).