Molecular-level chemical characterization and bioavailability of dissolved organic matter in stream water using electrospray-ionization mass spectrometry

Abstract

We used electrospray‐ionization mass spectrometry (ESI‐MS) to characterize, at the compound level, dissolved organic matter (DOM) composition and bioavailability in two streams. There was considerable consistency in the composition of the DOM between the two streams (unit mass resolution): ≫70% of the masses detected occurred in both streams. Approximately 40–50% of the bulk dissolved organic carbon in the stream water was bioavailable during a 12‐d microbial decomposition experiment. ESI‐MS compound level analysis identified which masses were used, which were not, and their patterns of utilization. In both streams, ~40% of the masses decreased in concentration, ~55% did not change, and ≪5% increased. Despite the complex system (≫1,500 DOM compounds and a natural consortia of bacteria), there was a high degree of similarity in which masses were used and the amount of each mass used between replicate flasks for a stream. There was also good agreement between the two streams in which masses were used and the amount of each mass used. This suggests that the selection by the microbial consortia of organic compounds in the complex and heretofore largely uncharacterized DOM pool is repeatable and, therefore, ultimately predictable.

Dynamics and Characterization of Refractory Dissolved Organic Matter Produced by a Pure Bacterial Culture in an Experimental Predator-Prey System

“…All compound-level analyses were performed using an Agilent 1100 liquid chromatography (LC) mass spectrometer equipped with an ESI source and a quadrupole mass selective detector (30,32). An autosampler introduced 20 l of individual sample into the LC mobile phase that went directly to the ESI source (no LC column was used).…”

“…Terrestrial and marine DOM pools have been characterized by ESI-MS (15,16,20,21). ESI-MS has also been used to gain insights into changes in DOM due to protozoan grazing (19), for characterization of DOM in rainwater (32), and to discriminate between possible refractory and labile DOM compounds in freshwater samples (30).…”

Bioavailability of dissolved organic nitrogen and carbon from nine rivers in the eastern United States

“…New techniques like electrosprayionization mass spectrometry show promise in providing the detailed molecular analysis needed for examining DOM dynamics. A recent study demonstrated that similar DOM masses from rivers with comparable land covers were consumed by bacteria during bioassay experiments (Seitzinger et al 2005). The next research step would be to determine if these DOM masses comprise the bioavailable DOM in rivers with different land-cover types.…”

Bioreactivity of estuarine dissolved organic matter: A combined geochemical and microbiological approach

“…While recent methodological advances have enhanced our ability to characterize dissolved OM (DOM) (Hansell and Carlson 2002 and references therein;Seitzinger et al 2005), such information only allows biologically reactive versus refractory components to be inferred across different, and often uncoupled, time and space scales. In contrast, microbial ecological studies have traditionally ignored DOM characterization at the molecular and substrate levels and relied instead on bioassays to predict the reactivity and availability of heterogeneous pools such as bulk OM to natural microbial populations (Benner 2003 and references therein; Sobczak et al 2002).…”