Radioisotope and chemical inhibitor measurements of dimethyl sulfide consumption rates and kinetics in estuarine waters

Abstract

Microbial consumption rates of 1 to 20 nM dimethyl sulfide (DMS) in estuanne wholewater samples from coastal Georgia (USA) were measured by 2 methods production of radiolabeled CO2 and particulates >O 2 pm from ('4CH,)2S, and specific inhibition by addition of 500 FM chloroform The combination and companson of these 2 methods helped overcome some inherent limitations of each one, and both methods gave short turnover times (< 1 d ) at low DMS concentrations (1 to 3 nM) DMS production was often as rapid as its consumption, suggesting very tight cycling However, when exogenous DMS was added to increase concentrations, consumption rates saturated below 20 nM, suggesting high affinities for DMS Kinehcs and rates appeared s m d a r over a several week penod in samples taken from the Duplin River, a coastal tidal nver where DMS concentrations were consistently in the range of 1 to 3 nM In contrast, samples of water whlch had recently flooded the marsh had much higher DMS concentrations, but consumption rates were simllar to those observed in the creek waters before they flooded the marsh The turnover tlmes calculated for the waters over the marsh were on the order of 3 to 7 d The radioisotope method showed that DMS assinillation into cell matenal was approximately equal to that respired as CO2, and confirmed 500 pM CHC13 as an excellent inhibitor of DMS consumption However it appears that chloroform may in some cases increase dissolved DMSP concentrations and hence DMS production, leading to overestimates of DMS consumption rates Two other inhibitors of DMS consumption, dimethyl disulfide (100 nM) and dimethyl ether (30 PM), gave similar but lower consumption rates compared to chloroform, and show promise as specif~c inhibitors for future studies

Temporal patterns of biological dimethylsulfide (DMS) consumption during laboratory-induced phytoplankton bloom cycles

“…3), but no such saturation was evident in the +nutrient carboy. Previous studies have observed saturation of seawater DMS consumption activity at low nanomolar concentrations (Kiene 1992, Wolfe & Kiene 1993. The data collected here suggest that the maximum consumption rates for DMS at a particular DMS concentration were stimulated by the nutrient amendment (and the resulting enhancement of phytoplankton biomass and bacterial production).…”

“…Wolfe & Kiene (1993) used 14 C-labeled DMS in waters from a salt marsh and found that the methyl carbons were assimilated into biomass and respired to CO 2 in roughly equal proportions (i.e. 50% carbon assimilation efficiency).…”

Annual DMSP contribution to S and C fluxes through phytoplankton and bacterioplankton in a NW Mediterranean coastal site

“…Surface waters were incubated for approximately 6 h in the dark at the in situ temperature in acid-rinsed, amber glass bottles (2.5 l) without any amendment (control treatment) and, simultaneously, with dimethyldisulfide (DMDS) addition (260 nmol l -1 final conc., DMDS treatment). Bottles were sampled for DMS at times 0, 2, 4, and 6 h. Assuming that DMDS selectively inhibits DMS consumption (Wolfe & Kiene 1993), the DMS consumption rate was obtained by the difference between the slope of DMS accumulation in the DMDS treatment (gross DMS production) and the slope of the time course of DMS concentration in the control treatment (net DMS produc-tion rate). For further details see Simó et al (2000) and Vila-Costa et al (2008).…”

Differential response of planktonic primary, bacterial, and dimethylsulfide production rates to static vs. dynamic light exposure in upper mixed-layer summer sea waters

“…dimethyldisulfide (Galí et al, 2011), an effective inhibitor of bacterial DMS consumption (Wolfe and Kiene, 1993;Simó et al, 2000). DMS photolysis was measured in 0.2 µm filtered-water incubations in 40 mL Teflon bottles or 50 mL quartz flasks.…”