“…protein-like fluorescence is likely derived from a mixture of dissolved amino acids and other organic materials with similar fluorescence characteristics (Maie et al 2007). …”
The biochemical composition of dissolved organic matter (DOM) strongly influences its biogeochemical role in freshwater ecosystems, yet DOM composition measurements are not routinely incorporated into ecological studies. To date, the majority of studies of freshwater ecosystems have relied on bulk analyses of dissolved organic carbon and nitrogen to obtain information about DOM cycling. The problem with this approach is that the biogeochemical significance of DOM can only partially be elucidated using bulk analyses alone because bulk measures cannot detect most carbon and nitrogen transformations. Advances in fluorescence spectroscopy provide an alternative to traditional approaches for characterizing aquatic DOM, and allow for the rapid and precise characterization of DOM necessary to more comprehensively trace DOM dynamics. It is within this context that we discuss the use of fluorescence spectroscopy to provide a novel approach to tackling a longstanding problem: understanding the dynamics and biogeochemical role of DOM. We highlight the utility of fluorescence characterization of DOM and provide examples of the potential range of applications for incorporating DOM fluorescence into ecological studies in the hope that this rapidly evolving technique will further our understanding of the biogeochemical role of DOM in freshwater ecosystems.
“…protein-like fluorescence is likely derived from a mixture of dissolved amino acids and other organic materials with similar fluorescence characteristics (Maie et al 2007). …”
The biochemical composition of dissolved organic matter (DOM) strongly influences its biogeochemical role in freshwater ecosystems, yet DOM composition measurements are not routinely incorporated into ecological studies. To date, the majority of studies of freshwater ecosystems have relied on bulk analyses of dissolved organic carbon and nitrogen to obtain information about DOM cycling. The problem with this approach is that the biogeochemical significance of DOM can only partially be elucidated using bulk analyses alone because bulk measures cannot detect most carbon and nitrogen transformations. Advances in fluorescence spectroscopy provide an alternative to traditional approaches for characterizing aquatic DOM, and allow for the rapid and precise characterization of DOM necessary to more comprehensively trace DOM dynamics. It is within this context that we discuss the use of fluorescence spectroscopy to provide a novel approach to tackling a longstanding problem: understanding the dynamics and biogeochemical role of DOM. We highlight the utility of fluorescence characterization of DOM and provide examples of the potential range of applications for incorporating DOM fluorescence into ecological studies in the hope that this rapidly evolving technique will further our understanding of the biogeochemical role of DOM in freshwater ecosystems.
“…Lignins ) and tannins (Maie et al, 2007) are measurable components in DOM that are thought to be important contributors to the humic-like fluorescence. Aromatic amino acids (Yamashita and Tanoue, 2003a) and phenolic structures (Maie et al, 2007;Stedmon and Nelson, 2015) within macromolecules such as lignins and tannins are potential contributors to the protein-like fluorescence. Tannins are highly reactive (Maie et al, 2006, thereby suggesting that lignins and aromatic amino acids are the major contributors to the humic-like and protein-like fluorescence, respectively.…”
Excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) is commonly used to investigate the dynamics of dissolved organic matter (DOM). However, a lack of direct comparisons with known biomolecules makes it difficult to substantiate the molecular composition of specific fluorescent components. Here, coincident surface-water measurements of EEMs, dissolved lignin, and total dissolved amino acids (TDAA) acquired in the northern Gulf of Mexico were used to investigate the relationships between specific fluorescent components and DOM biomolecules. Two terrestrial humic-like components identified by EEM-PARAFAC using samples obtained from river to offshore waters were strongly linearly correlated with dissolved lignin concentrations. In addition, changes in terrestrial humiclike abundance were correlated with those in lignin phenol composition, suggesting such components are largely derived from lignin and its alteration products. By applying EEM-PARAFAC to offshore samples, two protein-like components were obtained. The tryptophan-like component was strongly correlated with TDAA concentrations, corroborating the suggested protein/peptide origin of this component. The ratios of tryptophan-like component to tyrosine-like component or dissolved organic carbon (DOC) concentrations were also correlated with DOC-normalized yields of TDAA, suggesting these proxies are useful indicators of the bioavailability of DOM in marine waters of the studied ecosystem.
“…Several techniques exist to fractionate DOM based on size and one of the most commonly used one is size exclusion chromatography (SEC) (Chin et al 1997;Maie et al 2007;Woods et al 2010). HPLC based SEC has the advantage of providing chromatographic peaks of the chromophoric DOM (CDOM) and requires small sample size compared with other techniques such as tangential-flow ultrafiltration (Cai 1999).…”
Section: Molecular Size Based Characterization Ofmentioning
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