Hydrology influences carbon flux through metabolic pathways in the hypolimnion of a Mediterranean reservoir

Abstract Global change is modifying meteorological and hydrological factors that influence the thermal regime of water bodies. These modifications can lead to longer stratification periods with enlarged hypolimnetic anoxic periods, which promote heterotrophic anaerobic processes alter reservoir carbon cycling. Here, we quantified aerobic (aerobic respiration, denitrification, iron manganese reduction, sulfate methanogenesis) on dissolved inorganic (DIC) production in hypolimnion a Mediterranean (El Gergal, Spain) under two contrasting conditions: wet year heavy direct rainfall frequent inputs from upstream reservoirs, dry scarce negligible inputs. During year, induced low column stability earlier turnover. By contrast, was more stable during year. conditions, observed lower DIC accumulation hypolimnion, mainly due weaker reduction methanogenesis. promoted higher accumulation, resulting enhanced methanogenesis thus increasing methane emissions impairing quality. Aerobic denitrification metal produced similar amount studied years. All all, biological geochemical (calcite dissolution) explained most regardless but there still ~ 30% cannot be by contemplated this study assumptions made.