Hydrogen, carbon monoxide, and methane dynamics in Lake Constance

Abstract

The vertical distributions of dissolved H,, CO, and CH, and bacterial production (thymidine incorporation) were measured throughout 1987 in Lake Constance (Bodensee) and again in 1988 at a station in a small bight in the lake. Lake waters were supersaturated with respect to atmospheric H,, CO, and CH4, especially in the epilimnion; concentrations in the surface water showed a significant (P < 0.05) positive correlation with either autotrophic picoplankton, primary production, Chl a, pheophytin, or bacterial production. Dissolved H, and CO did not exhibit a distinct seasonal pattern, but dissolved CH, regularly increased during stratification and decreased in winter. Vertical profiles showed that surface maxima of CH, were not due to diffusion from methanogenic profundal sediment. Lateral transects and epilimnetic mass balance indicated that CH, may have originated from methanogenic littoral sediments along the shoreline and may also have been produced in oxic epilimnetic water by unknown processes. The water samples contained microbes able to oxidize HZ, CO, and CH4, but threshold concentrations required to sustain oxidation usually were higher than actual in situ concentrations of these gases. We therefore inferred that epilimnetic production of the gases was balanced by evasion to the atmosphere. With the stagnant film model, we determined that the mean residence times of the gases in the epilimniom were on the-order of 2-16 d.Hydrogen, carbon monoxide, and methane are reduced trace gases formed by anaerobic bacteria living in anoxic zones of aquatic environments. In contrast to the oceans, H2 and CO have been little studied in freshwater lakes (Conrad et al. 1983a,b;Dahm et al. 1983; Schiitz et al. 1988), and studies on CH, have concentrated on anoxic hypolimnions and anoxic-oxic interfaces of water columns (Rudd and Taylor 1980). The concentrations, origin, and turnover of these trace gases in the oxic epilimnia of lakes are largely unknown.Our laboratory has reported supersaturation of CH4, HZ, and CO in Lake Constance (Schuler et al. 1990). Here, we extend these observations considerably, providing a more complete picture of the vertical and seasonal

Dynamics of dissolved methane and methane oxidation in dimictic Lake Nojiri during winter

“…Compared with emission rates reported in other literature (5.4 mg m-* d-l in summer and 12 1.6 during fall overturn at Lake 227, Rudd and Hamilton 1978;31.3 in summer and 38.4 during fall overturn at Lake Mendota, Fallon et al 1980), Lake Nojiri fluxes during overturn period appear to be low. The diffusive fluxes in this study were comparable to or slightly lower than those measured by Schmidt and Conrad (1993) for Lake Constance, by de Angelis and Lilley (1987) for Oregon rivers, and by de Angelis and Scranton (1993) for the Hudson River.…”

“…The distribution of CH, and CH, oxidation activity has been studied in several eutrophic (e.g. Jannasch 1975;Rudd et al 1974;Rudd and Hamilton 1978;Harrits and Hanson 1980;Iversen et al 1987) and oligotrophic lakes (Lidstrom and Somers 1984;Lilley et al 1988;Schmidt and Conrad 1993). Most reports have focused on dimictic lakes that have a seasonally formed anaerobic layer in the hypolimnion, and the studies have been done during the period of summer stratification.…”

Oxic water column methanogenesis as a major component of aquatic CH4 fluxes

“…The relationship between CH 4 and phytoplankton observed here (Fig. 2) has been hypothesized before to explain both the presence of metabolically active methanogens, and the recurrent metalimnetic and near-surface CH 4 peaks in oxic lake 9,10,18,19 and marine [13][14][15][16][17] environments. We confirm this link experimentally, and further show that it generates a significant out flux of CH 4 from the mesocosms to the atmosphere (Fig.…”

“…This assumption certainly holds for small, shallow ecosystems where the surface layers are in relatively close contact with sediments. Yet CH 4 supersaturation is also prevalent in large, deep lakes 3,5,[7][8][9][10][11][12] and oceanic surface waters [13][14][15][16][17] , where deeper water columns result in significantly reduced surface water exchange with anoxic sediments. Studies of CH 4 dynamics in surface waters of oceans and large lakes have indeed concluded that pelagic CH 4 supersaturation cannot be sustained either by lateral inputs from the littoral or from benthic inputs alone 9,10,[13][14][15][17][18][19] .…”

“…At the same time, marine studies suggest that the microbial decomposition of methylated compounds such as methanethiol 15 and methylphosphonate 16,[23][24][25] could be an important source of CH 4 in surface waters of the open ocean. Further, metalimnetic peaks of CH 4 are a recurrent feature in many ecosystems, which correlate positively with dissolved O 2 (DO), algal biomass and production [8][9][10]14,15,18,19 . However, despite past efforts, the ecological and biogeochemical significance of oxic water column methanogenesis remain speculative, and we have yet to determine the dominant biochemical pathway, its controls, and its contribution to diffusive CH 4 emissions from aquatic ecosystems.…”