Dependence of Hypolimnetic Oxygen Consumption on Ambient Oxygen Concentration: Fact or Artifact?

Abstract

Ten lakes studied in this investigation and the data presented by previous authors are all consistent with the hypothesis that rates of oxygen depletion in the hypolimnion of lakes do not depend upon the ambient oxygen concentration over the range of concentrations from 12 mg/L to 1.0 mg/L. By definition, aerobic respiration must stop when there is no more oxygen present. Therefore the hypolimnetic oxygen deficit can be modeled as a zero‐order chemical process that is independent of oxygen concentration. Predictions of seasonal changes in hypolimnetic oxygen concentrations can be made by estimating the slope of the linear regression of oxygen concentration against the Julian day when the sample was collected.

Long‐term changes in the areal hypolimnetic oxygen deficit (AHOD) of Onondaga Lake: Evidence of sediment feedback

“…In multilake studies of oxygen depletion, Lasenby (1975) and Cornett and Rigler (1984) observed that hypolimnetic DO concentrations decreased linearly with time, suggesting that the process of hypolimnetic oxygen depletion is independent of the ambient DO concentration. However, evidence also exists that DO concentrations Ͻ2-3 mg L Ϫ1 cause lower depletion rates (Cornett and Rigler 1984;Campbell and Rigler 1986). Burns (1995) recommends that hypolimnetic oxygen depletion rates should not be calculated for hypolimnia with DO concentrations Ͻ2-3 mg L Ϫ1 .…”

“…Some authors reported that decomposition of organic material occurs more efficiently in the water column than at the sediment-water interface (Cornett and Rigler 1979;Charlton 1980b). This may contribute to the observation of Cornett and Rigler (1979) that lakes with thick hypolimnia have relatively high DO depletion rates, which is more of a concern in cross-sectional studies with lakes of widely different depths or when tracking a single system in which large differences in the volume of the hypolimnion occur one year to the next. It is not a noteworthy issue for Onondaga Lake because the thickness of the hypolimnion exhibited only modest variation during the 1978-2002 interval (mean 9.8 m, C.V. 0.14).…”

“…However, the strength of the cause and effect relationship between primary production and AHOD has been questioned (Cornett andRigler 1979, 1980;Charlton 1980a). A number of factors, unaccounted for in the traditional AHOD calculation (Wetzel and Likens 2000), have been identified that could affect hypolimnetic DO concentrations and limit the utility of AHOD as a comparative measure of primary production among lakes, including differences in (1) vertical density gradients within the metalimnion and related effects on the fraction of organic matter decomposed in the hypolimnion (Gliwicz 1979), (2) contributions of allochthonous organic material (Brezonik 1994), (3) thickness of the hypolimnion (Cornett andRigler 1979, 1980;Charlton 1980a), (4) temperature of the hypolimnion (Cornett andRigler 1979, 1980;Charlton 1980b), and (5) DO inputs to the hypolimnion from vertical mixing (Stauffer 1987). Burns (1995) expanded this listing of factors that can affect VHOD (or AHOD) to nine and included the delayed decomposition of organic material in sediments.…”

Using hypolimnetic dissolved oxygen depletion rates for monitoring lakes

“…Campbell & Rigler (1986) investigated the dependence of AT S on oxygen concentrations and they concluded that A" s was independent of ambient oxygen concentration above 3 g m~3, but that K^ varied with oxygen concentration below that level with the dependence showing up more strongly below 2 g m 3 . In experiments on the dependence of K w on ambient oxygen levels, Cornett & Rigler (1984) found dependence existed only below 2 g m~3.…”

“…However, there is much evidence to the contrary indicating that low DO concentrations cause low depletion rates (i.e., depletion rates are proportional to concentration and are thus first-order with respect to DO concentrations. ) Cornett & Rigler (1984) studied oxygen depletion in 10 lakes in Quebec, Canada, and observed the DO concentrations to decrease linearly with time while oxygen was present in adequate concentration. From this they concluded that "hypolimnetic oxygen deficit can be modelled as a zero-order chemical process that is independent of oxygen concentration".…”