Download or read book Decomposition of Dissolved Organic Matter in Arctic and Boreal Streams written by Audrey Mutschlecner and published by . This book was released on 2017 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic and boreal rivers connect terrestrial, oceanic, and atmospheric carbon (C) pools by transporting and processing dissolved organic matter (DOM). DOM composition influences its susceptibility to decomposition (biolability), which in turn determines whether the associated C is respired, stored, or exported. High-latitude ecosystems are changing rapidly due to processes such as permafrost thaw, shifts in vegetative communities, and increasing discharge, and each of these processes can influence the composition of DOM reaching rivers. The eventual fate of riverine DOM, whether it is mineralized or exported, shifts the balance of global C pools. Therefore, to understand how changes to high-latitude ecosystems influence the global C cycle, we must be able to connect patterns in DOM composition to its biolability and subsequent fate within the C cycle. The objectives of this study were to describe spatial and temporal patterns in DOM composition and biolability, and to determine links between the composition and biolability of DOM. I sampled DOM from streams along an Arctic-boreal gradient in interior Alaska throughout the year. I measured DOM biolability and nutrient limitation of decomposition in laboratory incubations and characterized DOM composition using optical properties and chemical analysis. I found that temporal patterns in DOM composition corresponded to seasonal trends in the hydrology of high-latitude catchments, linking DOM source to shallow, organic-rich flowpaths in spring and deeper groundwater flows in winter. Biolability was low, indicating that the majority of riverine DOM is recalcitrant to biological decomposition. I observed increased biolability in response to phosphorus (P) addition, particularly during spring, indicating that phosphorus limits DOM decomposition. To further examine the mechanisms driving C processing in streams, I also conducted a series of whole-stream experiments to compare the relative influence of molecular composition and nutrient content of DOM. I added leaf leachate to boreal streams and measured C retention, which represents both biological uptake and sorption. The leachates varied by molecular composition, due to differences in tissue chemistry of plant species, and in nutrient content, because the leaves were collected from plots with different fertilization regimes. Retention was greatest for leachates derived from trees that had been fertilized with P, indicating P-limitation of biological uptake of C or preferential sorption of P-containing organic molecules. Although leachates varied in molecular composition as determined by optical properties, these differences did not correspond to a difference in uptake rates by species. These patterns in DOM retention indicate that nutrient content is a greater constraint on C uptake than molecular composition. Together, the two studies suggest that export is the primary fate of ambient DOM in high-latitude streams, but that C processing is highly sensitive to inputs of bioavailable DOM. The coupling between the P and C cycles observed in both studies highlights the potential for nutrient availability to constrain or promote CO2 emissions from C-rich, high-latitude catchments.

Download or read book Sources Transportation and Utilization of Dissolved Organic Matter in Groundwater and Streams written by P. M. Wallis and published by Canada. Inland Waters Directorate, Water Quality Branch. This book was released on 1979 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: "It has long been recognized that streams in their natural state support a great deal more biomass than can be justified by primary production. This is believed to be the result of energy inputs to streams from terrestrial plants and animals which take the form of either Dissolved Organic Matter (DOM.45μ spherical diameter), or Particulate Organic Matter (POM.45μ)"--Introduction, page 1.

Download or read book Linking Optical and Chemical Properties of Dissolved Organic Matter in Natural Waters written by Christopher L. Osburn and published by Frontiers Media SA. This book was released on 2017-01-17 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: A substantial increase in the number of studies using the optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) as a proxy for its chemical properties in estuaries and the coastal and open ocean has occurred during the last decade. We are making progress on finding the actual chemical compounds or phenomena responsible for DOM’s optical properties. Ultrahigh resolution mass spectrometry, in particular, has made important progress in making the key connections between optics and chemistry. But serious questions remain and the last major special issue on DOM optics and chemistry occurred nearly 10 years ago. Controversies remain from the non-specific optical properties of DOM that are not linked to discrete sources, and sometimes provide conflicting information. The use of optics, which is relatively easier to employ in synoptic and high resolution sampling to determine chemistry, is a critical connection to make and can lead to major advances in our understanding of organic matter cycling in all aquatic ecosystems. The contentions and controversies raised by our poor understanding of the linkages between optics and chemistry of DOM are bottlenecks that need to be addressed and overcome.

Download or read book Dissolved Organic Matter in Arctic Watersheds and Coastal Waters written by Craig Thomas Connolly and published by . This book was released on 2019 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic warming is already affecting the movement of freshwater and dissolved organic matter (DOM) from watersheds to the coastal ocean in the Arctic. Improved understanding of DOM in freshwater sources and linkages to DOM characteristics in Arctic coastal waters is needed to assess responses to and feedbacks with climate change. This work focuses on DOM characteristics that couple watershed and coastal systems in the Arctic, with specific considerations of river and groundwater inputs to lagoon ecosystems along the eastern Alaska Beaufort Sea coast. We found that spring and summer river-borne concentrations of dissolved organic carbon and nitrogen (DOC and DON) are strongly linked to variations in watershed slope and soil organic matter coverage across space and scale in the Arctic. The quantities and composition of DOM in lagoons of the eastern Alaska Beaufort Sea coast vary markedly between seasons. Specifically, lagoons experience a shift from high to low DOC and DON concentrations between the late spring sea ice break-up and winter ice-covered periods, but these concentrations are more variable during the summer open water period. Distinct seasonal transitions in ice coverage, runoff from land, and water exchange with the Beaufort Sea strongly influence the availability of lagoon DOM. During the summer, concentrations of DOC and DON in supra-permafrost groundwater (SPGW) inputs to lagoons are much higher than those found in local rivers and lagoons. Late-summer fluxes of SPGW DOM to the northern Alaska coastline are substantial and may be the principal source of DOM to lagoons without river inputs. This SPGW DOM is sourced from readily leachable organic matter in surface soils and deeper soil horizons that likely extend into thawing permafrost. SPGW DOM contains aromatic carbon compounds that are largely resistant to microbial degradation on the order of days to months. While nearby river and lagoon water DOM has a similar composition and degradability, SPGW contains a portion of bioavailable and reactive DOM that is not present in river and lagoon waters. Inputs of SPGW DOM provide a potentially important source of energy for lagoon food webs along the Alaskan Beaufort Sea coast during the late summer

Download or read book Influence of Climate Change on the Changing Arctic and Sub Arctic Conditions written by Jacques Nihoul and published by Springer. This book was released on 2009-01-25 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years. The melting is accelerating, and researchers were unable to identify natural processes that might slow the deicing of the Arctic. Such substantial additional melting of Arctic and Antarctic glaciers and ice sheets would raise the sea level worldwide, flooding the coastal areas where many of the world's population lives. Studies, led by scientists at the National Center for Atmospheric Research (NCAR) and the University of Arizona, show that greenhouse gas increases over the next century could warm the Arctic by 3-5°C in summertime. Thus, Arctic summers by 2100 may be as warm as they were nearly 130,000 years ago, when sea levels eventually rose up to 6 m higher than today.

Download or read book Dissolved Organic Matter in Wetland Soils and Streams of Southeast Alaska written by Jason B. Fellman and published by . This book was released on 2008 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Dissolved organic matter (DOM) transported from terrestrial to aquatic ecosystems is an important source of C, N and energy for the metabolism of aquatic heterotrophic bacteria. I examined the concentration and chemical quality of DOM exported from coastal temperate watersheds in southeast Alaska to determine if wetland soils are an important source of biodegradable dissolved organic carbon (BDOC) to aquatic ecosystems. I addressed this question through a combination of high resolution temporal and spatial field measurements in three watersheds near Juneau, Alaska by using a replicated experimental design that characterized DOM export from three different soil types (bog, forested wetland and upland forest) within each of the watersheds. PARAFAC modeling of fluorescence excitation-emission spectroscopy and BDOC incubations were used to evaluate the chemical quality and lability of DOM. Overall, my findings show that wetland soils contribute substantial biodegradable DOM to streams and the response in BDOC delivery to streams changes seasonally, with soil type, and during episodic events such as stormflows. In particular, the chemical quality of DOM in streamwater and soil solution was similar during the spring runoff and fall wet season, as demonstrated by the similar contribution of protein-like fluorescence in soil solution and in streams. These findings indicate a tight coupling between wetland DOM source pools and streams is responsible for the export of BDOC from terrestrial ecosystems. Thus, seasonal changes in soil-stream linkages can have a major influence on watershed biogeochemistry with important implications for stream metabolism and the delivery of labile DOM to coastal ecosystems. Soil DOM additions in small streams draining the three soil types showed that DOM leached from watershed soils is readily used as a substrate by stream heterotrophs and at the same time modified in composition by the selective degradation of the proteinaceous fraction of DOM. These findings indicate terrestrial DOM inputs to streams are an important source of C to support stream heterotrophic production. Thus, the production of protein-rich, labile DOM and subsequent loss in stream runoff has the potential to be an important loss of C and N from coastal temperate watersheds"--Leaf iii.

Download or read book Aquatic Organic Matter Fluorescence written by Paula G. Coble and published by Cambridge University Press. This book was released on 2014-07-14 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: A core text on principles, laboratory/field methodologies, and data interpretation for fluorescence applications in aquatic science, for advanced students and researchers.

Download or read book Aquatic Ecosystems Interactivity of Dissolved Organic Matter written by Stuart Findlay and published by Academic Press. This book was released on 2003 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: Overviews of the source, supply and variability of DOM, surveys of the processes that mediate inputs to microbial food webs, and syntheses consolidating research findings provide a comprehensive review of what is known of DOM in freshwater. This book will be important to anyone interested in understanding the fundamental factors associated with DOM that control aquatic ecosystems."--BOOK JACKET.

Download or read book Controls on Microbial Processing of Dissolved Organic Matter in Boreal Forest Streams written by Marie Schmidt and published by . This book was released on 2020 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the boreal forest, permafrost thaw is resulting in changes in vegetation and deepening of watershed flowpaths. Caribou-Poker Creeks Research Watershed contains sub-catchments underlain with varying permafrost extents (4-53% cover), providing the opportunity to study how permafrost extent affects water chemistry and nutrient cycling. I measured nitrogen (N), phosphorous (P), and carbon (C) processing ectoenzyme activity in the water column and sediment of headwater streams, and related ectoenzyme activity to nutrient and dissolved organic carbon (DOC) concentration. Additionally, I used nutrient diffusing substrata (NDS) to grow biofilms with enhanced inorganic N and P and labile C alone and in combination and measured ectoenzyme activity and respiration of biofilms in response to resource amendments. High P-processing enzyme activity across streams of the CPCRW indicated microbial P limitation. Respiration and organic matter processing enzymes of biofilms grown on NDS increased with labile C or labile C in combination with nutrient additions, implying that labile C limited or co-limited rates of DOM processing. Our results suggest that as climate warming and subsequent permafrost thaw alters terrestrial inputs of dissolved organic matter (DOM) and inorganic nutrients into streams, changes in inorganic P and labile C availability will control microbial processing of DOM.

Download or read book Organic Matter Decomposition Rates in Arctic Soils written by L. A. & J. C. F. Tedrow Douglas and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Changes to Modern and Aged Dissolved Organic Matter Inputs Into the Kolyma River written by Jennifer A. Rogers and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is radically altering the Arctic. These alterations are expected to have immense and cascading implications on the carbon cycling of the region. In particular, our interest lies in the Kolyma River (KR) as it is the largest Arctic watershed entirely lined below with continuous organic-rich permafrost and is equally subject to shrubification. On one hand, it appears that permafrost is predicted to thaw with the potential to release large quantities of ancient organic carbon. On the other hand, nutrient liberation, increased moisture, and warming allow vegetation to colonize more effectively increasing modern sources of organic carbon. The decomposition of permafrost soil organic matter has been postulated to release permafrost-derived dissolved organic matter (DOM) into stream and riverine networks that is exceptionally old and aliphatic in nature. We aimed to improve the evaluation of permafrost dissolved organic carbon (DOC) inputs and fate by implementing ramped pyrolysis oxidation (RPO) and isotopic analysis coupled with ultrahigh-resolution mass spectrometry. Bioincubation analyses were fundamental in replicating the transformations that occur to DOM during riverine transport. We found that highly aliphatic molecular formulae identified in undegraded permafrost DOM contrasts with the comparatively aliphatic-poor composition of KR DOM, suggesting that limited quantities of undegraded permafrost DOM are present in the KR. RPO radiocarbon analysis of KR DOC fractions exhibited no "hidden" aged component indicative of permafrost influence. Consistent with radiocarbon results, thermostability analysis indicated limited biodegraded permafrost DOC in the KR. A mixing model allowed us to estimate permafrost inputs to the KR DOC. Ultimately, our findings highlight that export of modern terrestrial DOM is currently overwhelming any permafrost DOM signature in the KR. This emphasizes the important ramifications of vegetation changes on the composition and biolability of transported DOM in this region with increasing shrubs dominance over herbaceous vegetation and bare ground. To investigate this, we subjected leachates of representative vegetation and soils both to biodegradation incubations and analysis using ultrahigh-resolution mass spectrometry. Biolability was seen to primarily be driven by lower relative abundances of highly unsaturated and phenolic compounds and higher relative abundances of aliphatic compounds and an overall low nominal oxidation state of carbon. In particular, DOC derived from shrubs has a lower biolability when compared to non-woody vegetation, containing on average nearly half as much %BDOC. This indicates that this DOC may persist in the water column which may have large implications as we continue attempts to quantify a permafrost DOC flux. It may be that studies will need to appraise the role vegetation cover plays in altering the age and composition of DOM of a region before investigating inputs of aged sources.

Download or read book Pathways of Anaerobic Organic Matter Decomposition in Tundra Soils from Barrow Alaska written by and published by . This book was released on 2015 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation of tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at -2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. As a result, the decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.

Download or read book Geochemical Drivers of Organic Matter Decomposition in Arctic Tundra Soils written by and published by . This book was released on 2015 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns of dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.

Download or read book Dissolved Organic Matter Dynamics in an Arctic Catchment written by Kristin Eulene Judd and published by . This book was released on 2004 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissolved Organic Matter in Streams written by D.L. Lush and published by . This book was released on 1970 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Terrestrial and coloured dissolved organic matter in arctic waters written by and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissolved Organic Carbon written by Laura A. Garrett and published by . This book was released on 2001 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: