Hydrology and dissolved organic carbon biogeochemistry in an ombrotrophic bog

At the Mer Bleue bog, Ontario, Canada, DOC export measured at the basin out flow was -8.3 +/- 3.7 g C m(-2) yr(-1), and DOC loading via precipitation w as estimated to be 1.5 +/- 0.7 g C m(-2) yr(-1). Discharge and DOC export c alculated using a Dupuit-Forchheimer approximation compared weil (within 1 g C m(-2) yr(-1)) to outflow estimates of DOC export. and confirmed that ou tflow measurements were a suitable proxy for DOC seepage at the peatland ma rgins. DOC export was 12% of the magnitude of the residual carbon sink meas ured at the peatland. The [DOC] across groundwater transects decreased with depth, and [DOC] sampled below 0.75 m depths remained fairly constant over the study period. However, [DOC] exported through the acrotelm (0 to 0.45 m peat depth) was variable, ranging from 40 mg l(-1) after snowmelt to 70 m g l(-1) during the growing season. Fluorescence analysis revealed that expo rted DOC was 'allochthonous-like', whereas DOC in the catotelm (deeper laye rs of peat) became more 'autochthonous-like' with depth. A conceptual model is developed to summarize the hydrological processes and controls which af fect DOC biogeochemistry at the Mer Bleue. Copyright (C) 2001 John Wiley & Sons, Ltd.