Abstract
Organic matter mineralization rates were measured by the accumulation of DIC + CH 4 in the water overlying intact cores taken from littoral and protimdal sediments of nine Quebec lakes. The variability in areal carbon mineralization is much greater within lakes than among lakes varying in trophic richness. Organic matter mineralization in littoral sediments is more variable and, on average, threefold higher than in the profundal sediments. Sixty percent of the variation in mean summer mineralization rates is explained by site depth, a surrogate variable that incorporates the effect of temperature and may also be reflecting substrate quality and(or) supply. The lakes‐pecific characteristics most strongly correlated to the residuals of the regression with depth are catchment area‐to‐lake area ratio (CA:LA) and water residence time. In lakes with a larger CA:LA and a shorter residence time, the amount and(or) the quality of organic matter settling to the sediments at a given depth may be reduced, resulting in the lower observed mineralization rates. Total mineralization in the sediments is, not surprisingly, greater in larger lakes but the rate per unit area is smaller, reflecting the decreased importance of the littoral zone. More than half (54–100%) of the DIC + CH 4 produced in the sediments is from the littoral zone. Yet, because of the large biomass in epilinmetic waters, the littoral sediments account for