Short-term fall open system metabolism estimates were conducted in four stream locations in the Dubh Lochan watershed in late October/early November 2025. Methods involved placement of miniDOT dissolved oxygen data loggers in the thalweg of each stream for a minimum of 72 hours. Light was recorded (lux) using submerged data loggers (Hobo Pendant). Reaeration was analyzed empirically using the energy dissipation model. All sites were strongly heterotrophic (mean net daily metabolism and community respiration ranged from -2.4 to -3.8 and -1.3 to -3.7 g O2 m-2 24hr-1, respectively) and gross primary production was negligible. In-stream metabolic activity is almost entirely driven by heterotrophic respiration (e.g., microbial mineralization of organic carbon). This carbon is likely derived from allochthonous input of OM in the form of leaf litter and dissolved organic carbon. The Dubh Lochan outflow and Dubh Lochan downstream sites both were significantly more heterotrophic (p<0.05, ANOVA) relative to inflowing tributaries, likely due to the high concentration of dissolved organic carbon and other refractory dissolved compounds present therein and derived mainly from the dystrophic Dubh Lochan. This outflow consists of highly tanic and "stained" water. Free-water dissolved oxygen measurements taken at 1 and 8 meters below the surface of Dubh Lochan indicated strong heterotrophic conditions. The results of this short-term project indicate that the major tributary feeding Dubh Lochan is heterotrophic, and the accumulation and processing of OM in the Lochan likely drives higher levels of heterotrophy (e.g., CR was greater in the stream receiving Dubh Lochan outflow). Implications and outstanding questions include the following: What is the relative importance of legacy carbon derived from extensive peat formations in the headwaters vs. leaf-litter inputs for aquatic food webs? And how might these carbon sources fluctuate in the context of a changing climate? Site-specific research like this is critical, given that small, dystrophic lakes are common in boreal and subarctic bioregions, but are understudied.