Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

Abstract

Understanding how the concentration and chemical quality of dissolved organic matter (DOM) varies in soils is critical because DOM inXuences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation-emission Xuorescence spectroscopy, speciWc UV absorbance (SUVA 254 ) and biodegradable dissolved organic carbon (BDOC) incubations to investigate the chemical quality of DOM in soil water collected from 25 cm piezometers in four diVerent wetland and forest soils: bog, forested wetland, fen and upland forest. There were signiWcant diVerences in soil solution concentrations of dissolved organic C, N, and P, DOC:DON ratios, SUVA 254 and BDOC among the four soil types. Throughout the sampling period, average DOC concentrations in the four soil types ranged from 9-32 mg C l ¡1 and between 23-42% of the DOC was biodegradable. Seasonal patterns in dissolved nutrient concentrations and BDOC were observed in the three wetland types suggesting strong biotic controls over DOM concentrations in wetland soils. PARAFAC modeling of excitation-emission Xuorescence spectroscopy showed that protein-like Xuorescence was positively correlated (r 2 = 0.82; P < 0.001) with BDOC for all soil types taken together. This Wnding indicates that PARAFAC modeling may substantially improve the ability to predict BDOC in natural environments. Coincident measurements of DOM concentrations, BDOC and PARA-FAC modeling conWrmed that the four soil types contain DOM with distinct chemical properties and have unique Xuorescent Wngerprints. DOM inputs to streams from the four soil types therefore have the potential to alter stream biogeochemical processes diVerently by inXuencing temporal patterns in stream heterotrophic productivity.

Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources

“…In accordance with previous studies (Fellman et al, 2008), a similar share of the DOM pool in forest and mire drainage was biodegradable, indicated by the small variation in BCD-DOM across all samples (Table 1). Nonetheless, there was a large difference in the efficiency of carbon incorporation into biomass, with BGE varying fourfold ( Table 1).…”

Fluorescence spectroscopy opens new windows into dissolved organic matter dynamics in freshwater ecosystems: A review

“…Fellman et al (2009b) showed that protein-like fluorescence decreased downstream during soil leachate additions in forested headwater streams, whereas humic-like fluorescence did not change. These observed Stedmon et al (2003).…”

“…Protein-like components have considerable potential for use as biogeochemical tracers, as they have been used to predict DOM lability (Fellman et al 2009a) and to fingerprint DOM derived from microbial sources (Hood et al 2009). Although protein-like fluorescence has great potential for use in a range of ecological applications, much still needs to be learned, particularly in freshwater ecosystems with high DOM concentrations, about the molecular size (Maie et al 2007) and structure of DOM that contributes to protein-like fluorescence ).…”

“…Evaluation of DOM lability and biological activityProtein-like fluorescence has a range of potential applications in ecological studies through tracing its dynamics in the field or in laboratory experiments (Fellman et al 2008;Balcarczyk et al 2009;Lapworth et al 2009). For example, protein-like fluorescence has been correlated with bacterial production, bacterial respiration, and community respiration in southern Quebec lakes (Cammack et al 2004).…”

“…Another application for humic-like and protein-like fluorescence is for evaluating seasonal patterns in the source and composition of DOM (Jaffe et al 2008;Fellman et al 2009b;Miller and McKnight 2010). Jaffe et al (2008) showed that protein-like fluorescence reached its highest relative abundance during the summer in Florida Bay, indicating that primary production is responsible for the peak in protein-like fluorescence (Fig.…”