Long-term development of hypolimnetic oxygen depletion rates in the large Lake Constance

Abstract

This study investigates over 30 years of dissolved oxygen dynamics in the deep interior of Lake Constance (max. depth: 250 m). This lake supplies approximately four million people with drinking water and has undergone strong re-oligotrophication over the past decades. We calculated depth-specific annual oxygen depletion rates (ODRs) during the period of stratification and found that 50% of the observed variability in ODR was already explained by a simple separation into a sediment- and volume-related oxygen consumption. Adding a linear factor for water depth further improved the model indicating that oxygen depletion increased substantially along the depth. Two other factors turned out to significantly influence ODR: total phosphorus as a proxy for the lake's trophic state and mean oxygen concentration in the respective depth layer. Our analysis points to the importance of nutrient reductions as effective management measures to improve and protect the oxygen status of such large and deep lakes.

Lake thermal structure drives interannual variability in summer anoxia dynamics in a eutrophic lake over 37 years

“…The volumetric sink in lakes has been found to be strongly dependent on the trophic state of the lake, whereas the sediment sink is not (Rippey and Mc-Sorley, 2009). Eutrophic lakes tend to have high volumetric sinks that reach maxima of about 0.23 g m −3 d −1 (Rippey and McSorley, 2009), similar to the average volumetric sink of 0.16 g m −3 d −1 quantified by the deductive model for Lake Mendota. This finding is confirmed by the works of Conway (1972), who found that the high hypolimnetic oxygen demand of Lake Mendota was driven by algae decomposition originating from the surface layer.…”

“…This is likely due to the historically high autochthony of the eutrophic lake (Hart, 2017), with phytoplankton blooms documented back to the early 1900s (Lathrop, 2007), thereby minimizing the need for external nutrient loads to stimulate phytoplankton production. While biological contributions to volumetric and sediment oxygen demands are well described for a broad range of lakes (Gelda and Auer, 1996;Matzinger et al, 2010;Müller et al, 2012;Rippey and McSorley, 2009;Yuan and Jones, 2019), for eutrophic lakes the control over available organic substrate for hypolimnetic oxygen demand may depend more on internal processing (autochthony) than external subsidies (allochthony).…”

“…These oxygen depletion processes can be quantified as either a volumetric sink (e.g., due to organic matter mineralization in the water column) or as an areal sink (e.g., oxygen demand in the sediments). The depletion rates of oxygen depend on the organic matter pool (Müller et al, 2012(Müller et al, , 2019, the trophic status of the lake (Rhodes et al, 2017;Rippey and McSorley, 2009), the area to volume relationship over depth (Livingstone and Imboden, 1996), and the chemical demand of the water column and sediments (Yin et al, 2011).…”

Using small‐scale measurements to estimate hypolimnetic oxygen depletion in a deep lake

“…This allows for a more accurate description of the vertical structure of oxygen depletion. Rhodes et al () showed that the Livingstone and Imboden () model describes the oxygen depletion in Lake Constance below 150 m well. However, our results show that the highest variability in oxygen depletion can be observed above ∼ 150 m. Müller et al ( a ) describe the AHM based on a box model which takes F red and the SOU in the upper layer of the sediment into account.…”

“…This allows for a more accurate description of the vertical structure of oxygen depletion. Rhodes et al (2017) showed that the Livingstone and Imboden (1996) a is the ratio of sediment surface to water volume.…”