Previous analyses of larval chironomid δ13C have suggested that methanotrophic contribution to biomass is site-specific within lakes. We determined larval biomass, larval and methane gas stable carbon isotopes, and potential methane production from the sediments underlying different water column depths in Esthwaite Water, UK. Methane production increased whereas larval δ13C values typically became lighter with increasing lake depth. Reduced methane production at 15 m depth and correspondingly less13C-depleted larvae in the second year of study suggests that the rate of methane production influenced larval assimilation of methane-derived biomass. Larval distribution and other site-specific parameters, combined with two-source mixing models, were used to estimate potential methane-mediation via the abundant chironomid biomass to higher predators.