Download or read book Dynamics of Dissolved Organic Matter Composition in Scottish Rivers and Headwater Streams written by Sara Trojahn and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissolved Organic Matter Fluctuations in an Intermittent Headwater Stream written by Alba Guarch Ribot and published by . This book was released on 2017 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Dissolved organic matter (DOM) is an important source of carbon for aquatic microorganisms and it regulates many biogeochemical processes. Therefore, changes in river DOM concentration and properties could notably affect the functioning of fluvial and coastal ecosystems and alter the global carbon cycle. The DOM in headwater streams is strongly influenced by hydrology, as a consequence of the modification of catchment flow paths with high discharges. During storm events, the catchment hillsides are washed and terrigenous DOM is transported to rivers. In the Mediterranean region, the precipitation regime and evapotranspiration strongly modulate fluvial hydrology, which shows low discharges in summer and even flow disappearance. These dry–wet cycles of conditions affect many ecological and biogeochemical processes. In this thesis, I analyse a long time series of discharge and DOM data from Fuirosos, an intermittent headwater stream in NE Spain. My aim is to examine the relationship between DOM and hydrology at different temporal scales. First, I characterise the hydrological regime of this Mediterranean stream. A decrease in discharge was revealed, although trends in temperature and precipitation were not significant. In contrast, I did not find a clear temporal trend in dry period duration. However, rewetting has been significantly delayed, moving from September to October. The frequency of storm events decreased over the interval 1998–2015, showing a significant positive relationship with solar activity with a 2-year lag. Dissolved organic carbon (DOC) concentration saw a slight decrease during the study period, which was opposed to that observed in boreal systems. This pattern might respond to a reduction of terrigenous DOC input from forest hillsides as a consequence of the decrease in flushing episodes. The DOC temporal dynamics during the rewetting was regulated by dry period duration. Discharge oscillations explained up to 50% of total DOC variability during the wet period. Notably, this weight of discharge increased significantly over the years. DOM quality was also explored, and described in terms of absorbance and fluorescence properties. Most of the DOM properties were strongly related to discharge, revealing the input of allochthonous, degraded, aromatic, humic and large-molecular DOM under high flow conditions. However, these relationships were altered during drying and rewetting periods. The DOM responses at the individual storm event scale were highly heterogeneous. Multiple linear regression and commonality analyses showed that, in addition to the magnitude of storm episodes, antecedent hydrological conditions, namely pre-event basal flow and the magnitude of the previous storm event, played a significant role in regulating the trends and shapes of DOM–discharge hysteresis. Finally, I identified the differences and similarities in the DOM–discharge relationships between the intermittent Mediterranean stream analysed herein and a perennial Alpine stream with higher mean discharge (Oberer Seebach). The DOM in Fuirosos was significantly more concentrated, more terrigenous, more degraded, more aromatic and more humified. The sign of the global DOM–discharge response was the same in both streams. However, discharge was a more robust predictor of DOM variability in Oberer Seebach. In fact, low flow and rewetting periods in Fuirosos introduced considerable dispersion into the relationship. During snowmelt in Oberer Seebach the sensitivity to discharge also decreased or disappeared. The flushing/dilution patterns were essentially associated with the magnitude of storm events in Fuirosos. In contrast, the DOM quality change was more coupled to basal flow conditions in Oberer Seebach, while the storms were behind the DOC oscillations. This study attests to the importance of generating and analysing long-term and high-frequency biogeochemical series, which allow relationships between DOM and hydrology to be explored in intermittent headwater streams that are subjected to extreme hydrological regimes." -- TDX.

Download or read book Dissolved Organic Carbon Dynamics in Lakes and Streams in Northern Wisconsin written by Vanessa Czeszynski and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic carbon (DOC) is naturally occurring; however, various aspects of global climate change are increasing anthropogenic DOC in freshwater systems. Here we focus on lakes and streams in the Northern Lakes and Forests region of Wisconsin. This study aimed to 1) determine DOC concentration and composition in these systems, 2) compare DOC dynamics between system types and each month sampled, and 3) determine if relationships exist between DOC and nutrient quantities and microbial community production. This study found that DOC ranged from 2.62 - 61.35 mg/L, with no differences in DOC concentrations between the system types or months sampled. However, DOC composition differed greatly between system type and months, with lakes having more autochthonous carbon and streams having more allochthonous carbon (p

Download or read book Dissolved Organic Matter in Freshwater Ecosystems written by Penny J. Johnes and published by . This book was released on 2023-11-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Riparian Wetlands written by Eleni Geropanagioti and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microbial and Photochemical Cycling of Dissolved Organic Matter in Boreal Headwater Streams written by Doreen Franke and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is a key global energy source and carbon reservoir that links terrestrial and aquatic biogeochemical cycling. Allochthonous organic matter is abundant in boreal headwater streams, and environmental changes such as variation in nutrient availability and changes to watershed landscape composition have great potential for altering the DOM source, its composition and cycling. This dissertation focuses on two of the main drivers of aquatic carbon and nutrient cycling: the photochemical and the microbial processing of DOM in boreal headwater streams; specifically (i) how the photochemical lability of DOM varies between reaches within headwater streams, among headwater streams and an associated large river reach, (ii) how stream biofilm mineralization may be regulated by watershed organic matter source and composition, increased labile carbon, nitrogen, and phosphorus availability, and (iii) whether algal carbon sources are important to supporting stream biofilms and if such sources influence the use of allochthonous DOM in nutrient-enriched streams. The results suggest changes in landscape and nutrient availability have the potential to alter the photochemical and biogeochemical cycling of DOM. DOM photolability was increased upstream relative to downstream and the river DOM. This may be due to differences in DOM source and composition, and suggests losses in photolabile DOM downstream and in the lower reaches of the watershed. The phototransformation of DOM into low molecular weight compounds and nutrients such as ammonium is likely relevant to the carbon and nutrient cycling in boreal watersheds. Results here further suggest that boreal stream biofilm mineralization of DOM is regulated by watershed DOM source and composition. Labile carbon sources, such as algal inputs, may also play an important role in regulating DOM mineralization and the processing of nutrients by these biofilms. In nutrient-impacted streams, where primary production is high relative to nutrientpoor streams, biofilms may be stimulated to incorporate algal carbon sources. Yet in the boreal streams studied here, added labile carbon rarely enhanced the mineralization of extant stream DOM suggesting autotrophic-heterotrophic interactions represent a more important priming effect relative to changing DOM source in boreal streams.

Download or read book Dissolved Organic Matter Dynamics from Rivers to the Shelf Sea in East Anglia UK written by Chiara Cooper and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrologic Dynamics Control Dissolved Organic Matter Export from Watersheds written by Rebecca Anne Bellmore and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is an important component of nutrient cycling and energy transfer within and between ecosystems. Understanding controls over the magnitude and quality of DOM that is transferred from soils to surface water is needed to better characterize the terrestrial-aquatic carbon flux and effects of terrestrial DOM on downstream ecosystems. A meta-analysis of the response of in-stream dissolved organic nitrogen concentration (DON) to high flow events indicates that DON typically increases with flow across a wide range of ecosystem types, likely as novel DOM sources in the landscape are mobilized and transported to streams and rivers. Mechanisms controlling DOM export, including dissolved organic carbon (DOC) and DON concentrations and the quality of DOM, were examined in a small agricultural catchment in eastern Washington State. In the soil column, DOC concentration declined and source of DOM shifted from humic-like and plant-derived to microbially-derived with depth through the profile. Across seasons and years, DOM exported via drain discharge during low flows resembled that found deep in the soil profile, and DOM exported during high flows suggests topsoil and litter sources contribute to export. A simple mixing model suggests that litter leachate can contribute over 50% of DOM during peak flow. Based on modeled contributions of litter, topsoil and subsoil DOM during storm events, DOC concentration is over-predicted, except for peak flows, suggesting removal via sorption and/or microbial decomposition in the soil column control DOC export on the timescale of events. Although the character of exported DOM shifts with flow conditions, laboratory incubations suggest bioavailability to the stream sediment microbial community is consistently low, with a maximum of 7% loss over 6 days, indicating exported DOM is likely transported beyond the immediate stream reach. An analysis of anticipated effects of climate change on the flow regime in the catchment projects the wettest years to become more variable, with non-linear effects on the magnitude of DOC export. Finally I explore how climate change assessments can be incorporated into nonpoint source nutrient management plans, despite current uncertainty about the magnitude and timeframe of climate effects on nutrient loading.

Download or read book Dissolved Organic Matter Dynamics and Benthic Microbial Densities in the Upper Salmon River Idaho written by John R. Moeller and published by . This book was released on 1980 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissolved Organic Carbon Dynamics in Tallgrass Prairie Streams written by Sophie Alexandra Higgs and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Contrary to the previous notion that a stream acts primarily as the transporter of materials from land to oceans, research has shown that in-stream processing of organic matter and nutrients is significant and relevant at a global scale. Dissolved organic carbon (DOC) is the most abundant form of organic carbon in streams and has been demonstrated as an important source of energy supporting stream food webs. Understanding the dynamics of DOC in streams is, therefore, important in determining the contribution of flowing waters to global carbon storage and release. However, DOC exists as many different compounds, varying in source, composition, and quality. The composition of DOC that ends up in streams is partly controlled by the surrounding watershed, and landscape effects on DOC quality and quantity in streams have been observed. In the North American Tallgrass prairie, woody encroachment has led to changes in riparian vegetation, potentially altering the DOC received by the stream, and making it important to understand rates of DOC transformation as landscape alterations continue. The heterogeneity of the DOC pool makes it difficult to fully describe its components and to measure transformation rates. DOC uptake, or biological use, has been estimated through several methods including in-stream additions of various DOC sources and bottle incubations of stream water and sediments. One problem with addition methods for calculating uptake is that the DOC pool is difficult to replicate and additions of simple compounds or organic leachates do not represent total dissolved organic carbon (TDOC) dynamics. Another potential issue is that additions of a labile compound could potentially alter microbial activity through a priming effect and therefore distort ambient DOC uptake estimates. Finally, uptake parameters are mostly calculated assuming benthic uptake while recent studies have shown that planktonic uptake of DOC can also be significant. We conducted this study with these three considerations in mind. In the first chapter, we describe our use of in situ additions of glucose and bur oak leaf leachate in prairie stream reaches and concentrations of specific components to determine uptake dynamics of various specific DOC components, from a simple sugar to more complex plant compounds. We calculated uptake parameters of glucose and two different oak leaf components. We found that using glucose concentrations rather than TDOC concentrations, as has been done in previous studies, to measure uptake parameters resulted in higher uptake rates, indicating the importance of measuring the specific component added. Through leaf leachate additions, we found that an amino acid like component was consistently taken up faster than a humic-like component. The second chapter addresses the questions of uptake location and priming through a series of recirculating chamber incubations. We found that benthic uptake of leaf leachate was more important than that in the water column. Finally, elevated uptake of one leaf leachate component in the presence of glucose indicated a priming effect on microbial DOC uptake.

Download or read book Pulse of the Stream written by Catherine Grace Winters and published by . This book was released on 2016 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biotic and abiotic factors both play critical roles in the cycling of organic matter and nutrients in aquatic ecosystems. Understanding the relative control of these factors on solute fate and transport in fluvial systems is important for understanding how climatic changes can affect water quality. Many processes that control solute cycling in streams occur at sub-daily scales, making high-frequency, in situ, sub-hourly measurements important for capturing the response of dissolved organic matter and nutrients to changes in the strength of controlling processes. The tightly coupled aquatic and terrestrial environments present in headwater streams make them particularly useful systems for studying high-frequency changes in water chemistry. In this study, we examined the patterns of dissolved organic carbon, nitrate, dissolved oxygen, temperature, dissolved organic matter fluorescence, and stream discharge using in-stream measurements at sub-hourly to monthly time scales to understand the daily and seasonal controls of aquatic organic matter and nutrient processing. We also conducted a laboratory incubation to measure the effects of dissolved organic carbon and nutrient treatments on consumption of carbon and nitrogen in our system. Our main objectives were to identify: 1) the relative controls of diel biotic and abiotic processes on stream dissolved organic carbon and nitrate-N; and 2) the mechanisms controlling rapid autumnal changes in dissolved organic carbon and nitrate-N in stream runoff. We found that hydrology plays a key role in transporting solutes to a forested headwater stream in the Piedmont Region, Maryland; however, once solutes reach the stream biotic controls dominate the stream solute patterns. Biology is an important regulator of diel patterns of streamwater dissolved organic carbon and nitrate concentrations during springtime and autumn leaf fall. Diel cycling is most apparent during the spring prior to leaf out when the water temperature is increasing. Where patterns were evident, nitrate (annual average in second order stream: 17:00) and discharge (17:28) reached their minimums during the afternoon within a few hours of the peaks in dissolved oxygen (13:16), temperature (15:17), dissolved organic carbon (16:06), and dissolved organic matter fluorescence (17:23). Larger amplitudes of dissolved oxygen, nitrate, dissolved organic carbon, and dissolved organic matter fluorescence correspond with larger daily temperature changes. Laboratory incubations showed increased consumption of nitrogen in the presence of labile carbon, but not in the presence of labile carbon plus nutrients, which indicates our system is carbon limited. Autumn dissolved organic carbon and nitrate dynamics also indicate our system is carbon limited. Increased rates of leaf litter fall corresponded with increased consumption of stream nitrate leading to a late October depression, or annual minimum, in nitrate concentration. Storm events accelerated the recovery of stream nitrate to early autumn concentrations as nitrate was mobilized and transported from soils to the stream. Hydrology is important for solute transport to and export from the stream. Autotrophic activity dominates on the daily scale, while heterotrophic activity controls seasonal responses in organic matter and nutrient cycling in this forested watershed. Carbon and nitrogen dynamics have been studied in other forested systems, as well, but the controlling processes vary among these watershed. Our results highlight the importance of understanding controlling processes within specific watersheds when making large scale predictions of the potential export of carbon and nitrogen from forested systems.

Download or read book Dissolved Organic Matter Bioavailability and Composition in Streams Draining Catchments with Discontinuous Permafrost written by Kelly L. Balcarczyk and published by . This book was released on 2008 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: "We examined the influence of permafrost on dissolved organic matter (DOM) in Caribou Poker Creeks Research Watershed (CPCRW). We analyzed long-term data from watersheds underlain with varying degrees of permafrost, sampled springs and thermo karsts to capture the range of DOM concentration and quality, used fluorescence spectroscopy to examine DOM composition, and measured DOM bioavailabity. Permafrost hydrology influenced DOM patterns, with the stream draining the high permafrost watershed having the highest dissolved organic carbon and nitrogen (DOC and DON) concentrations, higher DOC:DON, and greater specific ultraviolet absorbance (SUVA). Streams, springs, and thermokarsts exhibited a wide range of DOC and DON concentrations (1.5 - 37.5 mgC/L and 0.14 - 1.26 mgN/L), DOC:DON (7.08 - 42.8), and SUVA (1.5 - 4.7 L mgC−1 m−1). All sites had fluorescence index values (1.3 - 1.4) consistent with DOM derived from terrestrial sources. Principal components analysis revealed distinct groups in our fluorescence data determined by diagenetic processing and DOM source. Bioavailability of DOM ranged from 2 - 35% and was correlated with the proportion of tyrosine and tryptophan. Our results indicate that the degradation of permafrost in CPCR W will result in a decrease in DOC and DON concentrations, a decline in DOC:DON, and a reduction in SUVA, accompanied by a change in bioavailability"--Leaf iii.

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 Quantity and Composition of Stream Dissolved Organic Matter in the Watershed of Conesus Lake New York written by Morgan Bida and published by . This book was released on 2013 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The watershed of Conesus Lake, New York is drained by more than 18 unique streams and several smaller tributaries and has multiple land uses, varying from highly agricultural to primarily wooded, making the lake an ideal study site for analysis of the effects of land use on various water quality parameters. Previous water quality and watershed-health studies at Conesus Lake have focused on the delivery of inorganic nutrients to the lake. We know much less, however, about the effects of watershed land use on the quantity and composition of dissolved organic matter (DOM) exported to the lake. We sought to determine how stream DOM quantity and composition varied with space and time within the watershed during 2011. The concentrations of dissolved organic carbon and inorganic and organic nitrogen and phosphorus were measured seasonally in 7 streams, with a more detailed analysis of water chemistry in 12 streams during the growing season. The composition of DOM entering Conesus Lake was assessed with a suite of optical indices and with fluorescence excitation-emission matrices (EEMs) with parallel factor analysis (PARAFAC), a chemometric technique for the decomposition of characteristic fluorescence peaks. A 4-component PARAFAC model showed one allochthonous, humic-like component (C1), one semi-labile component with allochthonous and/or autochthonous origin (C2), and two autochthonous, protein-like components (C3 & C4). We showed seasonality in the composition and quantity of DOM that is consistent with abiotic seasonal controls and principal components analyses (PCA) suggest that agriculturally-dominated streams are associated with increased nitrate and phosphate, a greater proportion of protein-like PARAFAC components (C3 & C4), and that the DOM tends to be less humified. These results imply that a) seasonal controls on DOM govern the abundance of protein-like DOM and can alter the quantity of bulk DOM, b) agricultural land use may augment autochthonous production in a stream, particularly in the spring and summer, thus creating a more labile pool of DOM that is exported to the lake, and c) stream order can alter DOM quantity and composition, possibly through instream processing and variations in light availability."--Abstract.

Download or read book Tracing the Dynamics of Dissolved Organic Matter in Marine Systems Exposed to Natuarl an D Experimental Perturbations written by Francisco Luis Aparicio-Bernat and published by . This book was released on 2016 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Understanding the Molecular Composition of Dissolved Organic Matter and Its Reactivity in the Environment written by Rajaa Mesfioui and published by . This book was released on 2014 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: