In situ dissolved organic carbon (DOC) release by submerged macrophyte-epiphyte communities in southern Quebec lakes

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte-epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C.m(-2).h(-1). Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C.m(-2).h(-1) (standard deviation (SD), +/- 0.65) or 56 mu g C.g dry weight(-1).h(-1) (SD, +/- 8), which we suggest can be used for extrapolations at the lake scale.