Ammonium and glucose amendments stimulate dissolved organic matter mineralization in a Lake Superior tributary

摘要: Dissolved organic matter (DOM) plays an integral role in the biogeochemical cycles of aquatic ecosystems, and rates DOM mineralization can be affected by nitrogen (N) carbon (C) availability water column. To determine if were limited N or C a small tributary Lake Superior, we conducted 28-day laboratory experiments where amended stream with microbial inoculum ammonium (NH4+) and/or glucose full factorial design. We repeated these on four dates (July, October, January, April) because expected nutrient limitation to vary temporal changes sources nutrients. stimulated additions NH4+ three all experiments, even October when inputs via leaf litter greatest. Mean biodegradable dissolved was greater July (40.6% ± 5.4) than (10.2% 0.9) January (9.6% 10.9) but did not differ from April (18.4% 0.7), which suggests composition varies temporally. Our results suggest that is exported this forested nearshore Superior throughout year, both nitrogen. Nutrient enrichment may alter in-stream processing streams, turn reducing export regions Great Lakes it fuels production.