Biogeochemistry of tropical lakes

Biogeochemical processes are driven jointly by mass flux and metabolism, but biogeochemical contrasts across latitude are more strongly related to metabolism than to mass flux. Metabolism can be expressed in terms of metabolic potential, which is regulated by temperature, irradiance, and chemical feedstocks (nutrients, electron acceptors, organic matter). Metabolic potential of autotrophs in tropical lakes for a given nutrient supply is 2–4 times higher than in lakes of middle latitude, mainly because tropical lakes have a higher rate of nutrient resupply to the mixed layer caused by their higher rates of vertical mass exchange between layers. Hypolimnetic waters of tropical lakes are warm and thus have much higher metabolic potential than hypolimnetic waters of midlatitude lakes. Oxic metabolism often is suppressed by rapid loss of oxygen during stratification in tropical lakes. Prominence of deepwater anoxia in the tropics magnifies the importance of biogeochemical processes involving electron acceptors other than oxygen.