RESPIRATORY QUOTIENTS PREDICT INCREASES IN REDUCING PRODUCTS IN THE HYPOLIMNION OF A STRATIFIED LAKE

The benthic respiration of Crystal Lake, Connecticut, was modeled with two respiratory quotients, the volumetric respiratory quotient (VRQ) and the fundamental respiratory quotient (FRQ). The VRQ is defined as the quotient of the increase in dissolved inorganic carbon (DIG) and t he decrease in dissolved oxygen (DO) resulting from respiration at a g iven depth. Those changes are relative to concentrations determined ea rly in spring. The FRQ is the slope of the regression of DIC against D O at all depths not chronically anoxic. Respiratory quotients describe the predominance of anaerobic over aerobic metabolism and should, the refore, predict the accumulation of the products of anaerobic metaboli sm (i.e., Fe2+, H2S). VRQs successfully predicted the increase in redu ced products in the hypolimnion of Crystal Lake. FRQs successfully pre dicted the rate of increase of reduced products early in stratificatio n. FRQ was unsuccessful in predicting the continued accumulation of re ducing products later in the summer, which may reflect a steady state between the production of DIC and reduced products and the diffusion o f oxygen across the thermocline, or may reflect methodological constra ints imposed by the calculation of FRQ. Both models were successful to a limited extent in predicting the accumulation of the products of an aerobic metabolism.