scholarly journals Evidence for the priming effect in a planktonic estuarine microbial community

2015 ◽  
Author(s):  
Andrew Decker Steen ◽  
Lauren N. M. Quigley ◽  
Alison Buchan
Keyword(s):  
Alkaline Phosphatase ◽  
Organic Matter ◽  
Organic Carbon ◽  
Priming Effect ◽  
Coastal Ocean ◽  
Aquatic Systems ◽  
Residence Times ◽  
Labile Organic Carbon ◽  
Recalcitrant Organic Matter

The "priming effect", in which addition of labile substances changes the remineralization rate of recalcitrant organic matter, has been intensively studied in soils, but is less well-documented in aquatic systems. We investigated the extent to which additions of nutrients or labile organic carbon could influence remineralization rates of 14C-labeled, microbially-degraded, phytoplankton-derived organic matter (OM) in microcosms inoculated with microbial communities drawn from Groves Creek Estuary in coastal Georgia, USA. We found that amendment with labile protein plus phosphorus increased remineralization rates of degraded, phytoplankton-derived OM by up to 100%, whereas acetate slightly decreased remineralization rates relative to an unamended control. Addition of ammonium and phosphate induced a smaller effect, whereas addition of ammonium alone had no effect. Counterintuitively, alkaline phosphatase activities increased in response to the addition of protein under P-replete conditions, indicating that production of enzymes unrelated to the labile priming compound may be a mechanism for the priming effect. The observed priming effect was transient: after 36 days of incubation roughly the same quantity of organic carbon had been mineralized in all treatments including no-addition controls. This timescale is on the order of the typical hydrologic residence times of well-flushed estuaries suggesting that priming in estuaries has the potential to influence whether OC is remineralized in situ or exported to the coastal ocean.

scholarly journals A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

2017 ◽  
Vol 14 (15) ◽  
pp. 3743-3762 ◽  
Author(s):  
Allison A. Oliver ◽  
Suzanne E. Tank ◽  
Ian Giesbrecht ◽  
Maartje C. Korver ◽  
William C. Floyd ◽  
...  
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Organic Carbon ◽  
Stream Water ◽  
Coastal Ocean ◽  
Stream Discharge ◽  
Coastal Margin ◽  
Doc Concentration ◽  
Small Catchments ◽  
Dom Composition

Abstract. The perhumid region of the coastal temperate rainforest (CTR) of Pacific North America is one of the wettest places on Earth and contains numerous small catchments that discharge freshwater and high concentrations of dissolved organic carbon (DOC) directly to the coastal ocean. However, empirical data on the flux and composition of DOC exported from these watersheds are scarce. We established monitoring stations at the outlets of seven catchments on Calvert and Hecate islands, British Columbia, which represent the rain-dominated hypermaritime region of the perhumid CTR. Over several years, we measured stream discharge, stream water DOC concentration, and stream water dissolved organic-matter (DOM) composition. Discharge and DOC concentrations were used to calculate DOC fluxes and yields, and DOM composition was characterized using absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). The areal estimate of annual DOC yield in water year 2015 was 33.3 Mg C km−2 yr−1, with individual watersheds ranging from an average of 24.1 to 37.7 Mg C km−2 yr−1. This represents some of the highest DOC yields to be measured at the coastal margin. We observed seasonality in the quantity and composition of exports, with the majority of DOC export occurring during the extended wet period (September–April). Stream flow from catchments reacted quickly to rain inputs, resulting in rapid export of relatively fresh, highly terrestrial-like DOM. DOC concentration and measures of DOM composition were related to stream discharge and stream temperature and correlated with watershed attributes, including the extent of lakes and wetlands, and the thickness of organic and mineral soil horizons. Our discovery of high DOC yields from these small catchments in the CTR is especially compelling as they deliver relatively fresh, highly terrestrial organic matter directly to the coastal ocean. Hypermaritime landscapes are common on the British Columbia coast, suggesting that this coastal margin may play an important role in the regional processing of carbon and in linking terrestrial carbon to marine ecosystems.

Using diffusive gradients in thin films to probe the kinetics of metal interaction with algal exudates

2011 ◽  
Vol 8 (5) ◽  
pp. 517 ◽  
Author(s):  
Jacqueline Levy ◽  
Hao Zhang ◽  
William Davison ◽  
Rene Groben
Keyword(s):  
Thin Films ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Chlorella Vulgaris ◽  
Metal Speciation ◽  
The Relationship ◽  
Diffusive Gradients ◽  
Kinetics Of

Environmental context Interaction of metals with dissolved organic matter is one of the key processes defining metal bioavailability in water. The technique of diffusive gradients in thin films was used to investigate the kinetics of the interaction between metals and dissolved organic matter released by algae. For most metals the rate at which they were released from the organic matter was fast, but release of iron was kinetically limited. AbstractThe interaction of metals with organic matter is one of the key processes determining metal speciation and bioavailability in water. Fulvic acid tends to dominate dissolved organic carbon (DOC) in freshwaters, but organic carbon produced in situ, e.g. exudates released by algae and bacteria, is also significant. The technique of diffusive gradients in thin films (DGT) was used to investigate the lability of metal–exudate complexes using a kinetic signature approach. Exudates were harvested from three cultured freshwater alga (Chlorella vulgaris, Cryptomonas pyrenoidifera, Anabaena flos-aquae) and the filtered media supplemented with trace metals. DGT-labile metal concentrations and kinetic signatures were determined (24-h deployment). The relationship between Fe and DOC was a defining feature of the kinetic signatures. Iron was the most kinetically limited metal followed by Al and Cu, whereas Co, Ni and Pb were effectively completely labile. Exudates from Chlorella vulgaris produced the most DOC and the most marked kinetic limitation.

In Situ Observations of the Occlusion of a Clay-Sugar Compound within Calcite

2022 ◽  
Author(s):  
Jialin Chi ◽  
Chonghao Jia ◽  
Wenjun Zhang ◽  
Christine V Putnis ◽  
Lijun Wang
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Global Climate Change ◽  
Global Climate ◽  
Ecological Systems ◽  
In Situ Observations ◽  
The Stability

The stability of soil organic matter (SOM) plays a key role in controlling global climate change as soil stores a large amount of organic carbon, compared with other ecological systems....

scholarly journals Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

2014 ◽  
Vol 11 (15) ◽  
pp. 4173-4190 ◽  
Author(s):  
B. P. Koch ◽  
G. Kattner ◽  
M. Witt ◽  
U. Passow
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Priming Effect ◽  
Control Variable ◽  
Ion Cyclotron Resonance ◽  
Potential Contribution ◽  
Transparent Exopolymer Particles ◽  
Degradation Rates ◽  
Algal Exudates

Abstract. The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5–9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L−1 year−1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L−1 d−1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our results led to several conclusions: (i) based on our experimental setup, higher substrate concentration resulted in a higher concentration of non-labile DOC; (ii) TEP, generated by bacteria, degrade rapidly, thus limiting their potential contribution to carbon sequestration; (iii) the molecular signatures of DOM derived from algal exudates and glucose after 70 days of incubation differed strongly from refractory DOM. After 2 years, however, the molecular patterns of DOM in glucose incubations were more similar to deep ocean DOM whereas the degraded exudate was still different.

Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass Spectrometry

Radiocarbon ◽  
2018 ◽  
Vol 61 (2) ◽  
pp. 395-413 ◽  
Author(s):  
Rui Bao ◽  
Ann P McNichol ◽  
Jordon D Hemingway ◽  
Mary C Lardie Gaylord ◽  
Timothy I Eglinton
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Organic Carbon ◽  
Acid Treatment ◽  
Inorganic Carbon ◽  
River Sediments ◽  
Labile Organic Carbon ◽  
Underlying Causes ◽  
High Carbonate ◽  
Acid Treatments

ABSTRACTIn practice, obtaining radiocarbon (14C) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting14C content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on14C content of sedimentary OM, we examine the variability in14C content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (RinseHCl) and HCl fumigation (FumeHCl)], we demonstrate that the two acid-treatments can affect14C content differentially. Our findings suggest that, for low-carbonate samples, RinseHClaffects the Fm values due to loss of young labile organic carbon (OC). FumeHClmakes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during RinseHCl, causing the Fm values of remaining OC to increase. FumeHClcan remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix.

scholarly journals Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)

2012 ◽  
Vol 9 (6) ◽  
pp. 2045-2062 ◽  
Author(s):  
S. Bouillon ◽  
A. Yambélé ◽  
R. G. M. Spencer ◽  
D. P. Gillikin ◽  
P. J. Hernes ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Seasonal Variations ◽  
Dissolved Inorganic Carbon ◽  
Low Flow ◽  
Tropical Rivers ◽  
Particulate Nitrogen ◽  
Congo River

Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions, consistent with major seasonal variations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q < 1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~30% higher and bicarbonate fluxes were ~35% lower than previous reports. DIC represented 58% of the total annual C flux, and under the assumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~50% of terrestrial-derived riverine C transport.

Impact of Riparian and Stream Restoration on Denitrification in Geomorphic Features of Agricultural Streams

2020 ◽  
Vol 63 (5) ◽  
pp. 1157-1167
Author(s):  
Molly K. Welsh ◽  
Sara K. McMillan ◽  
Philippe G. Vidon
Keyword(s):  
Organic Matter ◽  
Enzyme Activity ◽  
Organic Carbon ◽  
Riparian Vegetation ◽  
Dry Mass ◽  
Residence Times ◽  
Sediment Texture ◽  
Agricultural Streams ◽  
Geomorphic Features ◽  
Restoration Strategies

HighlightsDenitrification enzyme activity (DEA) was measured in stream sediments of restored and unrestored agricultural streams.Nitrate, sediment characteristics, riparian vegetation, and geomorphology influenced DEA.Pools at restored sites had lower organic carbon, coarser sediment textures, and lower denitrification potential.Restoration strategies should increase organic carbon and residence times through complex flowpaths.Abstract. Agricultural land use, channel modifications, and riparian vegetation composition can affect instream denitrification by altering geomorphic features, such as sediment texture, organic matter, retention time, and hyporheic exchange. Stream and riparian restoration is widely implemented in agricultural watersheds to mitigate excess nutrient export to sensitive downstream waters; however, the cumulative impact of channel reconstruction and altered channel and near-stream morphology on nitrogen dynamics remains poorly understood. We measured denitrification enzyme activity (DEA) and environmental variables (e.g., water chemistry, sediment texture, and organic matter) in different geomorphic features in agriculturally influenced streams in North Carolina with varied channel and riparian zone characteristics. Our results indicate that denitrification is primarily influenced by increased transport of nitrate (NO3-) to the streams in wetter months. Secondarily, structural factors, including riparian vegetation and stream geomorphology, impact denitrification by controlling the distribution of sediment texture and organic carbon. In the newly restored stream, we observed coarser streambed sediments and low sediment organic carbon, especially in scour pools constructed downstream from cross-vanes. Lower DEA was observed in restored pools (39.1 ng N g-1 dry mass h-1) compared to naturally occurring pools (70.7 to 278.1 ng N g-1 dry mass h-1). These results highlight the need for restoration strategies to be directed at increasing organic carbon and residence times through complex flowpaths (e.g., meanders, root wads, artificial woody debris dams). Keywords: Denitrification, Freshwater, Nitrogen, Restoration, Riparian, Stream, Water quality.

scholarly journals Temporal changes in photoreactivity of dissolved organic carbon and implications for aquatic carbon fluxes from peatlands

2017 ◽  
Vol 14 (7) ◽  
pp. 1793-1809 ◽  
Author(s):  
Amy E. Pickard ◽  
Kate V. Heal ◽  
Andrew R. McLeod ◽  
Kerry J. Dinsmore
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Samples ◽  
Stream Water ◽  
Direct Conversion ◽  
Aquatic Systems ◽  
Residence Times ◽  
Terrestrial Environment ◽  
Rainfall Events ◽  
Fluorescence Characteristics

Abstract. Aquatic systems draining peatland catchments receive a high loading of dissolved organic carbon (DOC) from the surrounding terrestrial environment. Whilst photo-processing is known to be an important process in the transformation of aquatic DOC, the drivers of temporal variability in this pathway are less well understood. In this study, 8 h laboratory irradiation experiments were conducted on water samples collected from two contrasting peatland aquatic systems in Scotland: a peatland stream and a reservoir in a catchment with high percentage peat cover. Samples were collected monthly at both sites from May 2014 to May 2015 and from the stream system during two rainfall events. DOC concentrations, absorbance properties and fluorescence characteristics were measured to investigate characteristics of the photochemically labile fraction of DOC. CO2 and CO produced by irradiation were also measured to determine gaseous photoproduction and intrinsic sample photoreactivity. Significant variation was seen in the photoreactivity of DOC between the two systems, with total irradiation-induced changes typically 2 orders of magnitude greater at the high-DOC stream site. This is attributed to longer water residence times in the reservoir rendering a higher proportion of the DOC recalcitrant to photo-processing. During the experimental irradiation, 7 % of DOC in the stream water samples was photochemically reactive and direct conversion to CO2 accounted for 46 % of the measured DOC loss. Rainfall events were identified as important in replenishing photoreactive material in the stream, with lignin phenol data indicating mobilisation of fresh DOC derived from woody vegetation in the upper catchment. This study shows that peatland catchments produce significant volumes of aromatic DOC and that photoreactivity of this DOC is greatest in headwater streams; however, an improved understanding of water residence times and DOC input–output along the source to sea aquatic pathway is required to determine the fate of peatland carbon.

Quantifying fluxes and characterizing compositional changes of dissolved organic matter in aquatic systems in situ using combined acoustic and optical measurements

2009 ◽  
Vol 7 (1) ◽  
pp. 119-131 ◽  
Author(s):  
Bryan D. Downing ◽  
Emmanuel Boss ◽  
Brian A. Bergamaschi ◽  
Jacob A. Fleck ◽  
Megan A. Lionberger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aquatic Systems ◽  
Optical Measurements ◽  
Compositional Changes
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