Comparison of a Simplified Cupric Oxide oxidation HPLC Method with the Traditional GC-MS Method for Characterization of Lignin Phenolics in Environmental Samples (vol 13, pg 1, 2015)

In our article entitled “Comparison of a simplified cupric oxide oxidation HPLC method with the traditional GC-MS method for characterization of lignin phenolics in environmental samples” (Limnol. Oceanogr.: Methods 13, 2015, 1–52), doi: 10.1002/lom3.10001, we would like to correct the errors in Fig. 2 and Table 2 as mentioned below. The label to Fig. 2(a) needs to be transposed as indicated in the corrected Fig. 2 image below

Effects of poisons and preservatives on the fluxes and elemental compositions of sediment trap materials

Bulk particle fluxes and organic elemental compositions were compared among sediment traps treated with different poisons and preservatives. The traps (3:1 open cylinders) were deployed for 1–2 months at 30 and 60 m depths in a coastal marine environment. The tested treatments included mercuric chloride, mixed antibiotics, sodium azide, formalin, chloroform, and salt, along with untreated controls. Fluxes of bulk particulate material and weight percentages of organic carbon measured for differently treated traps deployed simultaneously at the same depth both varied by an average of ±8% of the mean value. Great numbers of large (\u3e850 μm) zooplankton swimmers were removed by sieving from bulk sediment trap samples treated with formalin and mercuric chloride, and to a lesser extent from those treated with azide and chloroform. The \u3c850 μm “sediment” fractions of the formalin- and mercuric chloride-treated samples were characterized by slightly elevated %OC concentrations and lowered (C/N) ratios, apparently resulting from smaller swimmers that were not separated by sieving. Overall, problems involved with sample and treatment washout, and swimmer artifacts in poisoned traps affected measured fluxes and elemental compositions more than differences that could be clearly attributed to microbial degradation

Temporal Controls on Dissolved Organic Matter and Lignin Biogeochemistry in a Pristine Tropical River, Democratic Republic of Congo

Dissolved organic carbon (DOC), lignin biomarkers, and the optical properties of dissolved organic matter (DOM) were measured in the Epulu River (northeast Democratic Republic of Congo) with the aim of investigating temporal controls on the quantity and chemical composition of DOM in a tropical rainforest river. Three different periods defined by stages of the hydrologic regime of the region, (1) post dry flushing period, (2) intermediary period, and (3) start of the dry period/post flush, were sampled. Temporal variability in DOM quantity and quality was observed with highest DOC, lignin concentration (Σ8) and carbon‐normalized (Λ8) values during the flushing period attributed to greater surface runoff and leaching of organic‐rich horizons, with lowest values in the dry period/post flush once source materials were well leached. Chromophoric DOM (CDOM) was strongly correlated to DOC and Σ8 (r2 = 0.85 and 0.83, respectively; p \u3c 0.001), and CDOM quality measurements (SUVA254, spectral slope ratio and fluorescence index) were strongly correlated to Λ8 values (r2 = 0.77, 0.69, and 0.75, respectively; p \u3c 0.001), demonstrating the ability to derive DOC and lignin export and to track DOM quality in tropical riverine systems from simple optical measurements. This study demonstrates similar effects in the variability of DOM quantity and quality due to changing hydrologic inputs for a tropical river as has been previously reported for temperate and northern high‐latitude rivers. Therefore, flushing periods in tropical rivers warrant further study, as they are critical toward understanding ecosystem biogeochemistry as maximal export of freshly leached plant material occurs during this time period

Photochemical Degradation of Dissolved Organic Matter and Dissolved Lignin Phenols from the Congo River

Photochemical degradation of Congo River dissolved organic matter (DOM) was investigated to examine the fate of terrigenous DOM derived from tropical ecosystems. Tropical riverine DOM receives greater exposure to solar radiation, particularly in large river plumes discharging directly into the open ocean. Initial Congo River DOM exhibited dissolved organic carbon (DOC) concentration and compositional characteristics typical of organic rich blackwater systems. During a 57 day irradiation experiment, Congo River DOM was shown to be highly photoreactive with a decrease in DOC, chromophoric DOM (CDOM), lignin phenol concentrations (Σ8) and carbon-normalized yields (Λ8), equivalent to losses of ~45, 85–95, \u3e95 and \u3e95% of initial values, respectively, and a +3.1 % enrichment of the δ13C-DOC signature. The loss of Λ8 and enrichment of δ13C-DOC during irradiation was strongly correlated (r = 0.99, p \u3c 0.01) indicating tight coupling between these biomarkers. Furthermore, the loss of CDOM absorbance was correlated to the loss of Λ8 (e.g., a355 versus Λ8; r = 0.98, p \u3c 0.01) and δ13C-DOC (e.g., a355 versus δ13C; r = 0.97, p \u3c 0.01), highlighting the potential of CDOM absorbance measurements for delineating the photochemical degradation of lignin and thus terrigenous DOM. It is apparent that these commonly used measurements for examination of terrigenous DOM in the oceans have a higher rate of photochemical decay than the bulk DOC pool. Further process-based studies are required to determine the selective removal rates of these biomarkers for advancement of our understanding of the fate of this material in the ocean

Assessing the drivers of dissolved organic matter export from two contrasting lowland catchments, U.K

AbstractTwo lowland catchments in the U.K. were sampled throughout 2010–11 to investigate the dominant controls on dissolved organic matter quantity and composition. The catchments had marked differences in terms of nutrient status, land cover and contrasting lithologies resulting in differences in the dominant flow pathways (groundwater vs. surface water dominated). The Upper Wylye is a chalk stream with a baseflow index of 0.98, draining a catchment dominated by intensive agricultural production. Millersford Brook is a lowland peat catchment with a baseflow index of 0.43, draining a semi-natural catchment with heather moorland and coniferous forest. Samples were collected weekly between October 2010 and September 2011 from eleven sampling locations. Samples were analysed to determine dissolved organic carbon, nitrogen and phosphorus fractions with DOM composition evaluated via the DOC:DON ratio, DOC:DOP ratio, specific UV absorption at 254nm, absorbance ratio (a250:a365) and the spectral slope parameter between 350 and 400nm (S350–400). Significant differences were observed in all determinands between the catchments, over time, and spatially along nutrient enrichment and geoclimatic gradients. Seasonal variation in preferential flow pathways mobilising groundwater-derived DOM were identified as likely controls on the delivery of DOM in the permeable chalk dominated catchment. Steeper S350–400 values and elevated a250:a365 ratios in this catchment suggest material of a lower bulk aromatic C content and molecular weight delivered during the winter months when compared to the summer. DOC:DON ratios were markedly lower in the chalk catchment than the peatland catchment, reflecting the paucity of organic matter within the mineral soils of the chalk landscape, and higher fertiliser application rates. This manuscript highlights that DOM composition varies according to catchment landscape character and hydrological function

Tannin geochemistry of natural systems: method development and application

Thesis (Ph. D.)--University of Washington, 1999Polyphenolic tannin comprises a significant proportion of the leaves, needles, and barks of vascular plant tissues---all major contributors to terrigenous organic matter cycling in aquatic systems. However, virtually nothing is known at the molecular level about tannin diagenesis despite the increased sensitivity and unambiguity of molecular characterizations vs. bulk techniques. Due to the analytical challenges in measuring tannin molecularly, there has been little crossover to ecology from the large body of research in natural products. This thesis presents the development of a new method for molecular-level condensed tannin analysis, a survey of source tissues, and a geochemical application focussed on mangrove leaf diagenesis in a tropical estuary.The developed method consists of acid hydrolysis (HCl) of samples in acetone, water, and phloroglucinol as a nucleophile for carbocation capture. Analytes are partitioned into ethyl acetate, dried, trimethylsilyl derivatized, and quantified by gas chromatography. The method reproducibly yields intact terminal units and phloroglucinol-adducted extender units, in addition to flavones, flavanones, triterpenoids, and carboxylic acids.Molecular tannin signatures were obtained from 117 source tissues, including leaves, needles, woods, and barks from tropical and temperate forests, coasts, and grasslands. Conifer needles were distinguished by high prodelphinidin content while dicotyledon leaves alone yielded both triterpenoids and flavones. Barks were distinguished by flavanones and tetracosanoic acid.Molecular tannin in a degradation sequence of mangrove leaves ( Rhizophora mangle) revealed several important trends not evident by bulk techniques. Degree of polymerization (average chain length) highlighted early leaching processes and a subsequent shift toward abiotic or microbially-mediated chemical reactions. An increased degree of hydroxylation corresponded to increased degradation rate, a trend that may be indicative of changes in redox or pH conditions leading to quinone formation. The apparent inverse correlation between basic amino acids and molecular tannin might signal Schiff base reactions partially responsible for nitrogen immobilization. Measured molecular tannin was second in abundance only to carbohydrates in the senescent yellow leaves entering the estuarine system. Leaching losses of 30% tannin highlight the potential importance of tannin in dissolved organic matter.Based on these studies, molecular level tannin shows great promise as a tool for geochemical studies

Transport and Diagenesis of Dissolved and Particulate Terrigenous Organic Matter in the North Pacific Ocean

Lignin measurements were made on suspended particulate organic matter (POM), total dissolved organic matter (DOM), high-molecular-weight (HMW) DOM, and low-molecular-weight (LMW) DOM in the North Pacific at Station Aloha. Carbon-normalized yields of lignin and d13C measurements indicate that while terrigenous organic matter accounts only for B1 % of DOM in seawater, submicron POM has a substantial terrigenous component. The apparent size distribution and terrigenous nature of the particles is consistent with an aerosol source, but these particles could also be delivered to the ocean via rivers. Ratios of syringyl to vanillyl phenols as well as the fraction of dissolved lignin in HMWDOM provide molecular evidence of photochemical oxidation. Several differences in lignin composition and concentrations were evident between water masses. In particular, concentrations in North Pacific Intermediate Water were a factor of two greater than at all other depths. This is likely a reflection of higher riverine input via the Sea of Okhotsk. These trends suggest that lignin could serve as a general circulation tracer in addition to tracing riverine input and diagenetic processing of terrigenous organic matter in the ocean

The Transformation and Export of Organic Carbon Across an Arctic River‐Delta‐Ocean Continuum

The Arctic Ocean is surrounded by land that feeds highly seasonal rivers with water enriched in high concentrations of dissolved and particulate organic carbon (DOC and POC). Explicit estimates of the flux of organic carbon across the land-ocean interface are difficult to quantify and many interdependent processes makes source attribution difficult. A high-resolution 3-D biogeochemical model was built for the lower Yukon River and coastal ocean to estimate biogeochemical cycling across the land-ocean continuum. The model solves for complex reactions related to organic carbon transformation, including mechanistic photodegradation and multi-reactivity microbial processing, DOC-POC flocculation, and phytoplankton dynamics. The baseline DOC and POC flux out of the delta from April to September 2019, was 977 and 536 Gg C (∼80% of the annual total), but only 50% of the DOC and 25% of the POC exited the plume across the 10 m isobath. Microbial breakdown of DOC accounted for a net loss of 168 Gg C (17% of delta export) within the plume and photodegradation accounted for a net loss of 46.6 Gg C DOC (5% of delta export) in 2019. Flocculation decreased the total organic carbon flux by only 6.4 Gg C (∼1%), while POC sinking accounted for 63.3 Gg C (10%) settling in the plume. The loss of chromophoric dissolved organic matter due to photodegradation increased the light available for phytoplankton growth throughout the coastal ocean, demonstrating the secondary effects that organic carbon reactions can have on biological processes and the net coastal carbon flux