Seasonal change in microbial sulfur cycling in monomictic Lake Fukami‐ike, Japan

Abstract

Sulfur budgets and seasonal progression of sulfur cycling processes were investigated in Lake Fukami-ike, a small monomictic lake in Japan. The sulfur isotopic mass balance shows that the main sulfur source is groundwater inflow (d 34 S 5 215.0%). The sulfate influx is approximately 20% reduced by microbial sulfate reduction and deposited as sulfide (d 34 S 5 222.2%; 34 kmol yr 21 ); the remaining exits from the outflow channel (d 34 S 5 212.6%). In the water column, microbiological analyses reveal that green sulfur bacteria dominate more than 90% of the population in the anoxic layer. A monthly decrease in sulfate concentration at each depth indicates that sulfate reduction proceeds within the water column as a first-order reaction because of low sulfate concentration (, 600 mmol L 21 ). The isotopic fractionation factor of sulfate reduction is estimated to be 0.980 by the isotopic and concentration data of sulfate and sulfide from April to August. Numerical simulation indicates that the relative contribution of phototrophic sulfide oxidation is over 50 times slower than sulfate reduction from April to August but over two times higher from October to November because of lower sulfate conditions (, 300 mmol L 21 ). Sulfate concentration is the factor for controlling the relative contribution of sulfate reduction and phototrophic sulfide oxidation in monomictic lakes, which contrasts with that observed in permanently stratified lakes.

Sulfur isotope fractionation in modern euxinic systems: Implications for paleoenvironmental reconstructions of paired sulfate–sulfide isotope records

“…(<10&) in Archean sedimentary pyrites was due to the suppression of biologically imparted S isotope fractionation at low sulfate levels (>200 lM; Habicht et al, 2002), subsequent work has shown that MSR can impart substantial S isotope fractionations even at very low sulfate concentrations (Nakagawa et al, 2012;Gomes and Hurtgen, 2013;Crowe et al, 2014). Yet, it is still likely that Archean sulfate levels were low.…”

“…The mean e SR value at Lake Matano was determined by a reactive-diffusion model (Crowe et al, 2014). For Lake McCarrons (Gomes and Hurtgen, 2013) and Lake Fukami-ike (Nakagawa et al, 2012), a Rayleigh fractionation model was used to calculate e SR (after Mariotti et al, 1981). There was not sufficient water column d 34 S data to calculate e SR for Effingham Inlet and Tyro Basin.…”

Degree of high phenotypic plasticity in wild populations of Daphnia in early spring

“…Daphnia temporarily take refuge against Chaoborus larvae and fish in deep water columns or anoxic strata (Hanazato et al, 1989;Salonen and Lehtovaara, 1992;Spaak and Ringelberg, 1997;Vanderploeg et al, 2009;Larsson and Lampert, 2011). In fact, Daphnia in the study lake might also show this defensive behavior with diel vertical migration (DVM), since an anoxic layer was observed in this lake (Nakagawa et al, 2012;Suda et al, 2016). Chaoborus larvae also showed DVM in the lake against fish predation (Nagano et al, 2015).…”

“…The lake is a small monomictic eutrophic lake (Nakagawa et al, 2012;Suda et al, 2016). The circulation and stagnation periods were from November to March and April to October, respectively.…”

Sulfur Isotope Effects of Dissimilatory Sulfite Reductase

“…In laboratory experiments and natural marine and lacustrine systems, volumetric sulfate reduction rates scale primarily as a function of the availability of sulfate relative to common electron donors like organic carbon Goldhaber and Kaplan, 1975;Sim et al, 2011b;Leavitt et al, 2013). Indeed, sulfate can be non-limiting even in environments with as little as µM sulfate (Nakagawa et al, 2012;Gomes and Hurtgen, 2013;Crowe et al, 2014;Bradley et al, 2015), assuming organic matter is more limiting to allow a fractionation to occur (Wing and Halevy, 2014;Bradley et al, 2015). Constrained whole cell (in vivo) laboratory experiments demonstrate that when electron donors are limiting, the magnitude of fractionation between sulfate and sulfide ( 34 ε) carries a nonlinear inverse relationship with cell-specific sulfate reduction rates (Harrison and Thode, 1958;Kaplan and Rittenberg, 1964;Sim et al, 2011b;Leavitt et al, 2013).…”