Hypolimnetic oxygen depletion rates in deep lakes: Effects of trophic state and organic matter accumulation

Abstract

This study investigated the consumption of oxygen (O 2) in 11 European lakes ranging from 48 m to 372 m deep. In lakes less than~100 m deep, the main pathways for O 2 consumption were organic matter (OM) mineralization at the sediment surface and oxidation of reduced compounds diffusing up from the sediment. In deeper lakes, mineralization of OM transported through the water column to the sediment represented a greater proportion of O 2 consumption. This process predominated in the most productive lakes but declined with decreasing total phosphorous (TP) concentrations and hence primary production, when TP concentrations fell below a threshold value of~10 mg P m −3. Oxygen uptake by the sediment and the flux of reduced compounds from the sediment in these deep lakes were 7.9-10.6 and 0.6-3.6 mmol m −2 d −1 , respectively. These parameters did not depend on the lake's trophic state but did depend on sedimentation rates for the primarily allochthonous or already degraded OM. These results indicate that in lakes deeper than~100 m, mineralization of autochthonous OM is mostly complete by the time of sedimentary burial. This explains why hypolimnetic O 2 concentrations improve more rapidly following TP load reduction in deeper lakes relative to shallower lakes, where larger sediment-based O 2 consumption by settled OM and release of reduced substances may inhibit the restoration of hypolimnetic O 2 concentrations.

Trophic status and local conditions affect microbial potential for denitrification versus internal nitrogen cycling in lake sediments

“…Due to bottom water aeration, the O 2 concentration remained high in this lake. The rapid depletion of O 2 , NO 3 - , NO 2 - and SO 4 2- and the increasing concentration of NH 4 + with sediment depth indicated a high level of respiration activity, which is in line with previous reports 20, 42, 62 . Lake Sarnen, in contrast, showed similar sediment porewater profiles as other oligotrophic lakes, e.g., Lakes Lucerne 42 , Brienz, or Thun 62 .…”

“…The rapid depletion of O 2 , NO 3 - , NO 2 - and SO 4 2- and the increasing concentration of NH 4 + with sediment depth indicated a high level of respiration activity, which is in line with previous reports 20, 42, 62 . Lake Sarnen, in contrast, showed similar sediment porewater profiles as other oligotrophic lakes, e.g., Lakes Lucerne 42 , Brienz, or Thun 62 . However, compared to these lakes, the N compound concentrations in Lake Sarnen were lower, the O 2 and SO 4 2 concentrations, and O 2 penetration depth higher, which could be a sign of lower respiratory activity (Fig.…”

Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

“…The structural equation model shows a significant positive effect 503 between HRT and autochthonous POC, which can be explained by an increase in 504 phytoplankton photosynthesis (Crawford et al, 2016). Previous investigations have shown that autochthonous POC in lake reservoirs with depths greater than 100 m was completely mineralized before carbon burial (Steinsberger et al, 2020). Autochthonous POC can be rapidly used to produce CH4, while the decomposition of terrestrial POC was slower (Grasset et al, 2018;Isidorova et al, 2019 S10).…”

Loads of Pollution to Lake Toba and Their Impacts

“…The input of organic material is often not be considered in relation to the observation of lake waters condition. Meanwhile, as is known, organic material could have an impact on oxygen availability [25], especially in the hypolimnion zone, and the catchment area also contributes to the hypolimnion condition [26]. Thus, organic materials, which are indicators of domestic pollution, are important to be considered.…”