Journal articles: 'Estuarine sediments. Carbon sequestration'

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Van de Broek, Marijn, Stijn Temmerman, Roel Merckx, and Gerard Govers. "Controls on soil organic carbon stocks in tidal marshes along an estuarine salinity gradient." Biogeosciences 13, no. 24 (December 16, 2016): 6611–24. http://dx.doi.org/10.5194/bg-13-6611-2016.

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Abstract. Tidal marshes are sedimentary environments and are among the most productive ecosystems on Earth. As a consequence they have the potential to reduce atmospheric greenhouse gas concentrations by sequestering organic carbon (OC). In the past decades, most research on soil organic carbon (SOC) storage in marsh environments has focused on salt marshes, leaving carbon dynamics in brackish and freshwater marshes largely understudied and neglecting the diversity among tidal marshes. We therefore conducted an extensive sampling campaign to quantify and characterize SOC stock in marshes along a salinity gradient in the Scheldt estuary (Belgium and the Netherlands). We find that SOC stocks vary significantly along the estuary, from 46 in freshwater marshes to 10 kg OC m−2 in salt marshes. Our data also show that most existing studies underestimate total SOC stocks due to shallow soil sampling, which also influences reported patterns in OC storage along estuaries. In all sampled tidal marsh sediments the SOC concentration is more or less constant from a certain depth downward. However, this concentration decreases with increasing salinity, indicating that the amount of stable SOC decreases from the upper estuary towards the coast. Although the net primary production of macrophytes differs along the estuary, our data suggest that the differences in OC storage are caused mainly by variations in suspended sediment concentration and stable particulate OC (POC) content in the water along the estuary. The fraction of terrestrial suspended sediments and POC that is transported downstream of the maximum turbidity zone is very limited, contributing to smaller amounts of long-term OC sequestration in brackish and salt marsh sediments. In addition, high rates of sediment deposition on freshwater tidal marshes in the maximum turbidity zone promote efficient burial of OC in these marsh sediments.

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Lupker, Maarten, Christian France-Lanord, and Bruno Lartiges. "Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes." Earth Surface Dynamics 4, no. 3 (August 12, 2016): 675–84. http://dx.doi.org/10.5194/esurf-4-675-2016.

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Abstract. Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga–Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga–Brahmaputra is estimated ca. 6.5 meq 100 g−1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28 × 109 mol yr−1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga–Brahmaputra is responsible for an additional Ca2+ flux of 23 × 109 mol yr−1, while ca. 27 × 109 mol yr−1 of Na+, 8 × 109 mol yr−1 of Mg2+ and 4 × 109 mol yr−1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment–seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and its main effect is the sequestration of a significant fraction of the riverine Na flux to the oceans. The limited exchange fluxes of the Ganga–Brahmaputra relate to the lower than average CEC of its sediment load that do not counterbalance the high sediment flux to the oceans. This can be attributed to the nature of Himalayan river sediment such as low proportion of clays and organic matter.

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Novak, A. B., M. C. Pelletier, P. Colarusso, J. Simpson, M. N. Gutierrez, A. Arias-Ortiz, M. Charpentier, P. Masque, and P. Vella. "Factors Influencing Carbon Stocks and Accumulation Rates in Eelgrass Meadows Across New England, USA." Estuaries and Coasts 43, no. 8 (May 27, 2020): 2076–91. http://dx.doi.org/10.1007/s12237-020-00754-9.

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Abstract Increasing the protection of coastal vegetated ecosystems has been suggested as one strategy to compensate for increasing carbon dioxide (CO2) in the atmosphere as the capacity of these habitats to sequester and store carbon exceeds that of terrestrial habitats. Seagrasses are a group of foundation species that grow in shallow coastal and estuarine systems and have an exceptional ability to sequester and store large quantities of carbon in biomass and, particularly, in sediments. However, carbon stocks (Corg stocks) and carbon accumulation rates (Corg accumulation) in seagrass meadows are highly variable both spatially and temporally, making it difficult to extrapolate this strategy to areas where information is lacking. In this study, Corg stocks and Corg accumulation were determined at 11 eelgrass meadows across New England, representing a range of eutrophication and exposure conditions. In addition, the environmental factors and structural characteristics of meadows related to variation in Corg stocks were identified. The objectives were accomplished by assessing stable isotopes of δ13C and δ15N as well as %C and %N in plant tissues and sediments, measuring grain size and 210Pb of sediment cores, and through assessing site exposure. Variability in Corg stocks in seagrass meadows is well predicted using commonly measured environmental variables such as grain size distribution. This study allows incorporation of data and insights for the northwest Atlantic, where few studies on carbon sequestration by seagrasses have been conducted.

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Millar, Christina M., Adiza Ama Owusu Aduomih, Brett Still, and Mark H. Stolt. "Estuarine Subaqueous Soil Organic Carbon Accounting: Sequestration and Storage." Soil Science Society of America Journal 79, no. 2 (January 26, 2015): 389–97. http://dx.doi.org/10.2136/sssaj2014.05.0204.

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Gustafsson, Ö. "Sequestration of Black Carbon in Continental Shelf Sediments." Mineralogical Magazine 62A, no. 1 (1998): 555–56. http://dx.doi.org/10.1180/minmag.1998.62a.1.293.

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Waters, Matthew N., William F. Kenney, Mark Brenner, and Benjamin C. Webster. "Organic carbon sequestration in sediments of subtropical Florida lakes." PLOS ONE 14, no. 12 (December 13, 2019): e0226273. http://dx.doi.org/10.1371/journal.pone.0226273.

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Grgic, Marko, Jelena Beljin, Snezana Maletic, Marijana Kragulj-Isakovski, Jelena Trickovic, Tijana Zeremski, and Srdjan Roncevic. "Pentachlorobenzene sequestration in sediment by carbon rich amendment." Chemical Industry 73, no. 1 (2019): 63–73. http://dx.doi.org/10.2298/hemind1811140001g.

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Organic pollutants in sediments are a worldwide problem because sediments act as sinks for hydrophobic, toxic, persistent and bioaccumulative hazardous compoundssuch as penta-chlorobenzene (PeCB). PeCB can be involved in adsorption, desorption and transformation processes and can be made available to benthic organisms through the sediment?water interface. In order to reduce the risk, this study investigates effects of the dose and contact time between sediment and carbon-rich amendments (activated carbon (AC), biochar (BC) and hummus (HC)) on the effectiveness of detoxification. Four doses of carbon-rich amendments (0.5-10 %) and four equilibrations contact times (14 - 180 days) were investigated. The present research highlights the need for further examination and process optimization of different carbon-rich materials used for contaminant removal. Results have shown that the smallest dose (0.5 %) of investigated sorbents was sufficient to reduce the bioavailable fraction of PeCB below 5 %, and the ageing process after 14 days for AC and 30 days for HM and BC negligibly influenced the bioavailable fraction.

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Teng, Yihua, and Dongxiao Zhang. "Long-term viability of carbon sequestration in deep-sea sediments." Science Advances 4, no. 7 (July 2018): eaao6588. http://dx.doi.org/10.1126/sciadv.aao6588.

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Liu, Wen, Long Ma, Jilili Abuduwaili, Gulnura Issanova, and Galymzhan Saparov. "Sediment Organic Carbon Sequestration of Balkhash Lake in Central Asia." Sustainability 13, no. 17 (September 5, 2021): 9958. http://dx.doi.org/10.3390/su13179958.

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As an important part of the global carbon pool, lake carbon is of great significance in the global carbon cycle. Based on a study of the sedimentary proxies of Balkhash Lake, Central Asia’s largest lake, changes in the organic carbon sequestration in the lake sediments and their possible influence over the past 150 years were studied. The results suggested that the organic carbon in the sediments of Lake Balkhash comes mainly from aquatic plants. The organic carbon burial rate fluctuated from 8.16 to 30.04 g·m−2·a−1 and the minimum appeared at the top of the core. The organic carbon burial rate continues to decline as it has over the past 150 years. Global warming, higher hydrodynamic force, and low terrestrial input have not been conducive to the improvement of organic carbon sequestration in Balkhash Lake; the construction of a large reservoir had a greater impact on the sedimentary proxy of total organic carbon content, which could lead to a large deviation for environmental reconstruction. This is the first study to assess the sediment organic carbon sequestration using the modern sediments of Central Asia’s largest lake, which is of great scientific significance. The results contribute to an understanding of organic carbon sequestration in Central Asia and may provide a scientific basis for carbon balance assessment in regional and global scales.

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Schulte Ostermann, Tilla, Michael Kleyer, Maike Heuner, Elmar Fuchs, Stijn Temmerman, Ken Schoutens, J. Tjeerd Bouma, and Vanessa Minden. "Hydrodynamics affect plant traits in estuarine ecotones with impact on carbon sequestration potentials." Estuarine, Coastal and Shelf Science 259 (September 2021): 107464. http://dx.doi.org/10.1016/j.ecss.2021.107464.

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11

Ouyang, X., and S. Y. Lee. "Carbon accumulation rates in salt marsh sediments suggest high carbon storage capacity." Biogeosciences Discussions 10, no. 12 (December 6, 2013): 19155–88. http://dx.doi.org/10.5194/bgd-10-19155-2013.

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Abstract. Studies on carbon stock in salt marsh sediments are increasing. However, uncertainties exist in estimating global carbon storage in these vulnerable coastal habitats, thus hindering the assessment of their importance. Combining direct data and indirect estimation, this study compiled studies involving 158 sites across the southern and Northern Hemispheres, and estimated the global average carbon accumulation rate (CAR) at 242.2 g C m−2 yr−1 in saltmarsh sediments. Based on region-specific CAR and estimates of salt marsh area in various geographic regions between 40° S to 78.3° N, total CAR in global salt marsh sediments is ~ 10.1 Tg C yr−1. The data indicate that while the capacity for carbon sequestration by salt marsh sediments ranked the first amongst coastal wetland and forested terrestrial ecosystems, their carbon budget was the smallest due to their limited and declining global areal extent. However, there may be uncertainties for our global estimate owing to limited and patchy data availability. CAR of salt marsh sediments changes with latitude, tidal range, halophyte genera and elevation, with considerable variation among different biogeographic regions.

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Strand, Stuart E., and Gregory Benford. "Ocean Sequestration of Crop Residue Carbon: Recycling Fossil Fuel Carbon Back to Deep Sediments." Environmental Science & Technology 43, no. 4 (February 15, 2009): 1000–1007. http://dx.doi.org/10.1021/es8015556.

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Torres-Alvarado, María del Rocío, Francisco José Fernández, Florina Ramírez Vives, and Francisco Varona-Cordero. "Dynamics of the Methanogenic Archaea in Tropical Estuarine Sediments." Archaea 2013 (2013): 1–13. http://dx.doi.org/10.1155/2013/582646.

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Methanogenesis may represent a key process in the terminal phases of anaerobic organic matter mineralization in sediments of coastal lagoons. The aim of the present work was to study the temporal and spatial dynamics of methanogenic archaea in sediments of tropical coastal lagoons and their relationship with environmental changes in order to determine how these influence methanogenic community. Sediment samples were collected during the dry (February, May, and early June) and rainy seasons (July, October, and November). Microbiological analysis included the quantification of viable methanogenic archaea (MA) with three substrates and the evaluation of kinetic activity from acetate in the presence and absence of sulfate. The environmental variables assessed were temperature, pH, Eh, salinity, sulfate, solids content, organic carbon, and carbohydrates. MA abundance was significantly higher in the rainy season (106–107 cells/g) compared with the dry season (104–106 cells/g), with methanol as an important substrate. At spatial level, MA were detected in the two layers analyzed, and no important variations were observed either in MA abundance or activity. Salinity, sulfate, solids, organic carbon, and Eh were the environmental variables related to methanogenic community. A conceptual model is proposed to explain the dynamics of the MA.

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Ezcurra, Paula, Exequiel Ezcurra, Pedro P. Garcillán, Matthew T. Costa, and Octavio Aburto-Oropeza. "Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage." Proceedings of the National Academy of Sciences 113, no. 16 (March 28, 2016): 4404–9. http://dx.doi.org/10.1073/pnas.1519774113.

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Given their relatively small area, mangroves and their organic sediments are of disproportionate importance to global carbon sequestration and carbon storage. Peat deposition and preservation allows some mangroves to accrete vertically and keep pace with sea-level rise by growing on their own root remains. In this study we show that mangroves in desert inlets in the coasts of the Baja California have been accumulating root peat for nearly 2,000 y and harbor a belowground carbon content of 900–34,00 Mg C/ha, with an average value of 1,130 (± 128) Mg C/ha, and a belowground carbon accumulation similar to that found under some of the tallest tropical mangroves in the Mexican Pacific coast. The depth–age curve for the mangrove sediments of Baja California indicates that sea level in the peninsula has been rising at a mean rate of 0.70 mm/y (± 0.07) during the last 17 centuries, a value similar to the rates of sea-level rise estimated for the Caribbean during a comparable period. By accreting on their own accumulated peat, these desert mangroves store large amounts of carbon in their sediments. We estimate that mangroves and halophyte scrubs in Mexico’s arid northwest, with less than 1% of the terrestrial area, store in their belowground sediments around 28% of the total belowground carbon pool of the whole region.

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Kao, S. J., R. G. Hilton, K. Selvaraj, M. Dai, F. Zehetner, J. C. Huang, S. C. Hsu, et al. "Preservation of terrestrial organic carbon in marine sediments offshore Taiwan: mountain building and atmospheric carbon dioxide sequestration." Earth Surface Dynamics 2, no. 1 (March 4, 2014): 127–39. http://dx.doi.org/10.5194/esurf-2-127-2014.

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Abstract. Geological sequestration of atmospheric carbon dioxide (CO2) can be achieved by the erosion of organic carbon (OC) from the terrestrial biosphere and its burial in long-lived marine sediments. Rivers on mountain islands of Oceania in the western Pacific have very high rates of OC export to the ocean, yet its preservation offshore remains poorly constrained. Here we use the OC content (Corg, %), radiocarbon (Δ 14Corg) and stable isotope (δ13Corg) composition of sediments offshore Taiwan to assess the fate of terrestrial OC, using surface, sub-surface and Holocene sediments. We account for rock-derived OC to assess the preservation of OC eroded from the terrestrial biosphere and the associated CO2 sink during flood discharges (hyperpycnal river plumes) and when river inputs are dispersed more widely (hypopycnal). The Corg, Δ14Corg and δ 13Corg of marine sediment traps and cores indicate that during flood discharges, terrestrial OC can be transferred efficiently down submarine canyons to the deep ocean and accumulates offshore with little evidence for terrestrial OC loss. In marine sediments fed by dispersive river inputs, the Corg, Δ14Corg and δ 13Corg are consistent with mixing of terrestrial OC with marine OC and suggest that efficient preservation of terrestrial OC (>70%) is also associated with hypopycnal delivery. Sub-surface and Holocene sediments indicate that this preservation is long-lived on millennial timescales. Re-burial of rock-derived OC is pervasive. Our findings from Taiwan suggest that erosion and offshore burial of OC from the terrestrial biosphere may sequester >8 TgC yr−1 across Oceania, a significant geological CO2 sink which requires better constraint. We postulate that mountain islands of Oceania provide a strong link between tectonic uplift and the carbon cycle, one moderated by the climatic variability which controls terrestrial OC delivery to the ocean.

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Zhang, Jing. "Effect of Black Carbon in Soil and Sediment on Organic Chemical Sorption and Carbon Sequestration." Advanced Materials Research 668 (March 2013): 194–98. http://dx.doi.org/10.4028/www.scientific.net/amr.668.194.

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Environmental black carbon (BC) in soils and sediments has received increasing attention due to the sorption for organic chemicals and the potentials for carbon sequestration. In this work, pyrene sorption to humic acid and BC fractions in sediment was investigated by using extracted humic acid and preheated sediment, respectively. Thermally labile organic matter was removed during preheating and the remaining fraction of organic carbon (OC) is recognized as BC. The comparison results highlighted the important role of BC in pyrene sorption, especially at low concentrations. In addition, the micro-porosity of pristine and preheated sediments was analyzed by CO2 sorption. The blocking effect of associated humic substances on the micro-pores of BC for CO2 sorption was not observed. On the contrary, the probed micro-pore volume was higher in the case of pristine sediment, which implies the sorption of CO2 molecules by humic substances.

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Macreadie, Peter I., Katie Allen, Brendan P. Kelaher, Peter J. Ralph, and Charles G. Skilbeck. "Paleoreconstruction of estuarine sediments reveal human‐induced weakening of coastal carbon sinks." Global Change Biology 18, no. 3 (November 23, 2011): 891–901. http://dx.doi.org/10.1111/j.1365-2486.2011.02582.x.

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Plummer, Patrick, Craig Tobias, and David Cady. "Nitrogen reduction pathways in estuarine sediments: Influences of organic carbon and sulfide." Journal of Geophysical Research: Biogeosciences 120, no. 10 (October 2015): 1958–72. http://dx.doi.org/10.1002/2015jg003057.

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Duarte, Carlos M. "Reviews and syntheses: Hidden forests, the role of vegetated coastal habitats in the ocean carbon budget." Biogeosciences 14, no. 2 (January 23, 2017): 301–10. http://dx.doi.org/10.5194/bg-14-301-2017.

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Abstract. Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr−1, representing between 3 % and 1∕3 of oceanic CO2 uptake. Up to 1∕2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

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Adhikari, Subhendu, Rattan Lal, and Bharat Chandra Sahu. "Carbon sequestration in the bottom sediments of aquaculture ponds of Orissa, India." Ecological Engineering 47 (October 2012): 198–202. http://dx.doi.org/10.1016/j.ecoleng.2012.06.007.

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Boyd, Claude E., C. Wesley Wood, Philip L. Chaney, and Julio F. Queiroz. "Role of aquaculture pond sediments in sequestration of annual global carbon emissions." Environmental Pollution 158, no. 8 (August 2010): 2537–40. http://dx.doi.org/10.1016/j.envpol.2010.04.025.

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Yu, Shuman, and Shun Uchida. "Geomechanical effects of carbon sequestration as CO2 hydrates and CO2-N2 hydrates on host submarine sediments." E3S Web of Conferences 205 (2020): 11003. http://dx.doi.org/10.1051/e3sconf/202020511003.

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Over the past 10 years, more than 300 trillion kg of carbon dioxide (CO2) have been emitted into the atmosphere, deemed responsible for climate change. The capture and storage of CO2 has been therefore attracting research interests globally. CO2 injection in submarine sediments can provide a way of CO2 sequestration as solid hydrates in sediments by reacting with pore water. However, CO2 hydrate formation may occur relatively fast, resulting decreasing CO2 injectivity. In response, nitrogen (N2) addition has been suggested to prevent potential blockage through slower CO2-N2 hydrate formation process. Although there have been studies to explore this technique in methane hydrate recovery, little attention is paid to CO2 storage efficiency and geomechanical responses of host marine sediments. To better understand carbon sequestration efficiency via hydrate formation and related sediment geomechanical behaviour, this study presents numerical simulations for single well injection of pure CO2 and CO2-N2 mixture into submarine sediments. The results show that CO2-N2 mixture injection improves the efficiency of CO2 storage while maintaining relatively small deformation, which highlights the importance of injectivity and hydrate formation rate for CO2 storage as solid hydrates in submarine sediments.

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Amano, Koji, and Takehiko Fukushima. "On the Longitudinal and Vertical Changes in Lake Estuarine Sediments." Water Science and Technology 20, no. 6-7 (June 1, 1988): 143–53. http://dx.doi.org/10.2166/wst.1988.0198.

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In order to obtain environmental information about lake water and watersheds, the vertical and longitudinal distributions of physical and chemical properties in lake sediments were investigated. The concentrations of several substances (e.g., nutrients, metals, and chemicals) in the sediments were determined at fifty sampling sites in sixteen shallow lakes in Japan. The vertical profiles of particle size, particle organic carbon, particle organic nitrogen, total phosphorus, some metals (Ti, Mn, Fe, Zn, and Cu), and LAS were analysed. Various sediment properties, such as the sedimentation conditions and the redox conditions, were related to the vertical profiles observed, and traces of historical changes in the water and watersheds were found in the sediments. Longitudinal changes in the sediments between the mouths of the rivers and the deepest points of the lakes were clearly observed, and it was expected that these changes would correlate with one of the estuarine characteristics since they reflect the spatial variation in average composition of the particulate matter and in the average water quality. Some significant relationships between the lake sediments and the lake or watershed type were observed, indicating the possibility that lake sediments may be one of the most important indices for understanding lake environments.

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Simone, Michelle N., Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre. "Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean." Biogeosciences 18, no. 5 (March 16, 2021): 1823–38. http://dx.doi.org/10.5194/bg-18-1823-2021.

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Abstract. Relative to their surface area, estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors of temperature change (from Δ−3 to Δ+5 ∘C compared to ambient mean temperatures) and ocean acidification (OA, ∼ 2× current CO2 partial pressure, pCO2) was investigated ex situ. Warming alone increased sediment heterotrophy, resulting in a proportional increase in sediment DOC uptake; sediments became net sinks of DOC (3.5 to 8.8 mmol C m−2 d−1) at warmer temperatures (Δ+3 and Δ+5 ∘C, respectively). This temperature response changed under OA conditions, with sediments becoming more autotrophic and a greater sink of DOC (up to 4× greater than under current pCO2 conditions). This response was attributed to the stimulation of heterotrophic bacteria with the autochthonous production of labile organic matter by microphytobenthos. Extrapolating these results to the global area of unvegetated subtidal estuarine sediments, we find that the future climate of warming (Δ+3 ∘C) and OA may decrease estuarine export of DOC by ∼ 80 % (∼ 150 Tg C yr−1) and have a disproportionately large impact on the global DOC budget.

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Bartoli, Marco, Sara Benelli, Monia Magri, Cristina Ribaudo, Paula Carpintero Moraes, and Giuseppe Castaldelli. "Contrasting Effects of Bioturbation Studied in Intact and Reconstructed Estuarine Sediments." Water 12, no. 11 (November 7, 2020): 3125. http://dx.doi.org/10.3390/w12113125.

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Macrofauna can produce contrasting biogeochemical effects in intact and reconstructed sediments. We measured benthic fluxes of oxygen, inorganic carbon, and nitrogen and denitrification rates in intact sediments dominated by a filter and a deposit feeder and in reconstructed sediments added with increasing densities of the same organisms. Measurements in reconstructed sediments were carried out 5 days after macrofauna addition. The degree of stimulation of the measured fluxes in the intact and reconstructed sediments was then compared. Results confirmed that high densities of bioturbating macrofauna produce profound effects on sediment biogeochemistry, enhancing benthic respiration and ammonium recycling by up to a factor of ~3 and ~9, respectively, as compared to control sediments. The deposit feeder also increased total denitrification by a factor of ~2, whereas the filter feeder activity did not stimulate nitrogen removal. Moreover, the effects of deposit feeders on benthic fluxes were significantly higher (e.g., on respiration and ammonium recycling) or different (e.g., on denitrification) when measured in intact and reconstructed sediments. In intact sediments, deposit feeders enhanced the denitrification coupled to nitrification and had no effects on the denitrification of water column nitrate, whereas in reconstructed sediments, the opposite was true. This may reflect active burrowing in reconstructed sediments and the long time needed for slow growing nitrifiers to develop within burrows. Results suggest that, in bioturbation studies, oversimplified experimental approaches and insufficient preincubation time might lead to wrong interpretation of the role of macrofauna in sediment biogeochemistry, far from that occurring in nature.

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Sánchez-García, Laura, Ingemar Cato, and Örjan Gustafsson. "The sequestration sink of soot black carbon in the Northern European Shelf sediments." Global Biogeochemical Cycles 26, no. 1 (January 6, 2012): n/a. http://dx.doi.org/10.1029/2010gb003956.

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Dicen, Gerald P., Ian A. Navarrete, Roland V. Rallos, Severino G. Salmo, and Maria Carmela A. Garcia. "The role of reactive iron in long-term carbon sequestration in mangrove sediments." Journal of Soils and Sediments 19, no. 1 (June 13, 2018): 501–10. http://dx.doi.org/10.1007/s11368-018-2051-y.

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Kao, S. J., R. G. Hilton, K. Selvaraj, M. Dai, F. Zehetner, J. C. Huang, S. C. Hsu, et al. "Preservation of terrestrial organic carbon in marine sediments off shore Taiwan: mountain building and atmospheric carbon dioxide sequestration." Earth Surface Dynamics Discussions 1, no. 1 (July 17, 2013): 177–206. http://dx.doi.org/10.5194/esurfd-1-177-2013.

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Abstract. Geological sequestration of atmospheric carbon dioxide (CO2) can be achieved by the erosion of organic carbon (OC) from the terrestrial biosphere and its burial in long-lived marine sediments. Rivers on mountain islands of Oceania in the western Pacific have very high rates of OC export to the ocean, yet its preservation offshore remains poorly constrained. Here we use the OC content (Corg, %), radiocarbon (Δ14Corg) and stable isotope (δ13Corg) composition of sediments offshore Taiwan to assess the fate of terrestrial OC. We account for rock-derived fossil OC to assess the preservation of OC eroded from the terrestrial biosphere (non-fossil OC) during flood discharges (hyperpycnal river plumes) and when river inputs are dispersed more widely (hypopycnal). The Corg, Δ14Corg and δ13Corg of marine sediment traps and cores indicate that during flood discharges, terrestrial OC is transferred efficiently to the deep ocean and accumulates offshore with little evidence for terrestrial OC loss. In marine sediments fed by dispersive river inputs, the Corg, Δ14Corg and δ13Corg are consistent with mixing of marine OC and terrestrial OC and suggest that efficient preservation of terrestrial OC (> 70%) is also associated with hypopycnal delivery. Re-burial of fossil OC is pervasive. Our findings from Taiwan suggest that erosion and marine burial of terrestrial non-fossil OC may sequester > 8 TgC yr−1 across Oceania, a significant geological CO2 sink which requires better constraint. We postulate that mountain islands of Oceania provide strong link between tectonic uplift and the carbon cycle, one moderated by the climatic variability that controls terrestrial OC delivery to the ocean.

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Adame, M. F., N. S. Santini, C. Tovilla, A. Vázquez-Lule, L. Castro, and M. Guevara. "Carbon stocks and soil sequestration rates of tropical riverine wetlands." Biogeosciences 12, no. 12 (June 23, 2015): 3805–18. http://dx.doi.org/10.5194/bg-12-3805-2015.

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Abstract. Riverine wetlands are created and transformed by geomorphological processes that determine their vegetation composition, primary production and soil accretion, all of which are likely to influence C stocks. Here, we compared ecosystem C stocks (trees, soil and downed wood) and soil N stocks of different types of riverine wetlands (marsh, peat swamp forest and mangroves) whose distribution spans from an environment dominated by river forces to an estuarine environment dominated by coastal processes. We also estimated soil C sequestration rates of mangroves on the basis of soil C accumulation. We predicted that C stocks in mangroves and peat swamps would be larger than marshes, and that C, N stocks and C sequestration rates would be larger in the upper compared to the lower estuary. Mean C stocks in mangroves and peat swamps (784.5 ± 73.5 and 722.2 ± 63.6 MgC ha−1, respectively) were higher than those of marshes (336.5 ± 38.3 MgC ha−1). Soil C and N stocks of mangroves were highest in the upper estuary and decreased towards the lower estuary. C stock variability within mangroves was much lower in the upper estuary (range 744–912 MgC ha−1) compared to the intermediate and lower estuary (range 537–1115 MgC ha−1) probably as a result of a highly dynamic coastline. Soil C sequestration values were 1.3 ± 0.2 MgC ha−1 yr−1 and were similar across sites. Estimations of C stocks within large areas need to include spatial variability related to vegetation composition and geomorphological setting to accurately reflect variability within riverine wetlands.

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Moens, Tom, Steven Bouillon, and Fabiane Gallucci. "Dual stable isotope abundances unravel trophic position of estuarine nematodes." Journal of the Marine Biological Association of the United Kingdom 85, no. 6 (November 9, 2005): 1401–7. http://dx.doi.org/10.1017/s0025315405012580.

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The role and quantitative importance of free-living nematodes in marine and estuarine soft sediments remain enigmatic for lack of empirical evidence on the feeding habits and trophic position of most nematode species. Here we use natural abundances of carbon and nitrogen stable isotopes of some abundant nematode species/genera from estuarine intertidal sediments to assess their trophic level and major food sources. In all stations, δ15N of different dominant nematode species/genera spanned a range of 3.6 to 6.3 ppt, indicating that at least two trophic levels were represented. The large nematodes Enoplus brevis, Enoploides longispiculosus and Adoncholaimus fuscus consistently had high δ15N, in line with mouth-morphology based predictions and empirical evidence on their predacious feeding modes. Daptonema sp., Metachromadora remanei, Praeacanthonchus punctatus and ‘Chromadoridae’ (dominated by Ptycholaimellus ponticus) had comparatively lower δ15N, and δ13C suggesting that microphytobenthos (MPB) is their major carbon source, although freshly sedimented particulate organic matter may also contribute to their nutrition in silty sediments. The trophic position of Sphaerolaimus sp., a genus with documented predacious feeding mode, was ambiguous. Ascolaimus elongatus had δ15N signatures indicating a predacious ecology, which is at variance with expectations from existing feeding type classifications. Our study shows that—despite limitations imposed by the biomass requirements for EA-IRMS (elemental analyser—isotope ratio mass spectrometry)—natural isotope abundances of carbon and nitrogen are powerful tools to unravel trophic structure within nematode communities. At the same time, the prominence of different trophic levels results in a large span of δ15N, largely invalidating the use of nitrogen isotope abundances to assess food sources and trophic level of whole nematode communities.

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Ouyang, X., and S. Y. Lee. "Updated estimates of carbon accumulation rates in coastal marsh sediments." Biogeosciences 11, no. 18 (September 19, 2014): 5057–71. http://dx.doi.org/10.5194/bg-11-5057-2014.

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Abstract. Studies on carbon stock in salt marsh sediments have increased since the review by Chmura et al. (2003). However, uncertainties exist in estimating global carbon storage in these vulnerable coastal habitats, thus hindering the assessment of their importance. Combining direct data and indirect estimation, this study compiled studies involving 143 sites across the Southern and Northern hemispheres, and provides an updated estimate of the global average carbon accumulation rate (CAR) at 244.7 g C m−2 yr−1 in salt marsh sediments. Based on region-specific CAR and estimates of salt marsh area in various geographic regions between 40° S to 69.7° N, total CAR in global salt marsh sediments is estimated at ~10.2 Tg C yr−1. Latitude, tidal range and elevation appear to be important drivers for CAR of salt marsh sediments, with considerable variation among different biogeographic regions. The data indicate that while the capacity for carbon sequestration by salt marsh sediments ranked the first amongst coastal wetland and forested terrestrial ecosystems, their carbon budget was the smallest due to their limited and declining global areal extent. However, some uncertainties remain for our global estimate owing to limited data availability.

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Faux, Jessica F., Laura L. Belicka, and H. Rodger Harvey. "Organic sources and carbon sequestration in Holocene shelf sediments from the western Arctic Ocean." Continental Shelf Research 31, no. 11 (August 2011): 1169–79. http://dx.doi.org/10.1016/j.csr.2011.04.001.

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Faust, Johan C., Mark A. Stevenson, Geoffrey D. Abbott, Jochen Knies, Allyson Tessin, Isobel Mannion, Ailbe Ford, Robert Hilton, Jeffrey Peakall, and Christian März. "Does Arctic warming reduce preservation of organic matter in Barents Sea sediments?" Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2181 (August 31, 2020): 20190364. http://dx.doi.org/10.1098/rsta.2019.0364.

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Over the last few decades, the Barents Sea experienced substantial warming, an expansion of relatively warm Atlantic water and a reduction in sea ice cover. This environmental change forces the entire Barents Sea ecosystem to adapt and restructure and therefore changes in pelagic–benthic coupling, organic matter sedimentation and long-term carbon sequestration are expected. Here we combine new and existing organic and inorganic geochemical surface sediment data from the western Barents Sea and show a clear link between the modern ecosystem structure, sea ice cover and the organic carbon and CaCO 3 contents in Barents Sea surface sediments. Furthermore, we discuss the sources of total and reactive iron phases and evaluate the spatial distribution of organic carbon bound to reactive iron. Consistent with a recent global estimate we find that on average 21.0 ± 8.3 per cent of the total organic carbon is associated to reactive iron (fOC-Fe R ) in Barents Sea surface sediments. The spatial distribution of fOC-Fe R , however, seems to be unrelated to sea ice cover, Atlantic water inflow or proximity to land. Future Arctic warming might, therefore, neither increase nor decrease the burial rates of iron-associated organic carbon. However, our results also imply that ongoing sea ice reduction and the associated alteration of vertical carbon fluxes might cause accompanied shifts in the Barents Sea surface sedimentary organic carbon content, which might result in overall reduced carbon sequestration in the future. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning’.

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Alavaisha, Edmond, and Mwita M. Mangora. "Carbon Stocks in the Small Estuarine Mangroves of Geza and Mtimbwani, Tanga, Tanzania." International Journal of Forestry Research 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/2068283.

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Mangrove forests offer important ecosystem services, including their high capacity for carbon sequestration and stocking. However, they face rapid degradation and loss of ecological resilience particularly at local scales due to human pressure. We conducted inventory of mangrove forests to characterise forest stand structure and estimate carbon stocks in the small estuarine mangroves of Geza and Mtimbwani in Tanga, Tanzania. Forest structure, above-ground carbon (AGC), and below-ground carbon (BGC) were characterised. Soil carbon was estimated to 1 m depth using loss on ignition procedure. Six common mangrove species were identified dominated byAvicennia marina(Forsk.) Vierh. andRhizophora mucronataLamarck. Forest stand density and basal area were 1740 stems ha−1and 17.2 m2 ha−1for Geza and 2334 stems ha−1and 30.3 m2 ha−1for Mtimbwani. Total ecosystem carbon stocks were 414.6 Mg C ha−1for Geza and 684.9 Mg C ha−1for Mtimbwani. Soil carbon contributed over 65% of these stocks, decreasing with depth. Mid zones of the mangrove stands had highest carbon stocks. These data demonstrate that studied mangroves are potential for carbon projects and provide the baseline for monitoring, reporting, and verification (MRV) to support the projects.

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Corbett, D. R. "Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary." Biogeosciences 7, no. 10 (October 26, 2010): 3289–300. http://dx.doi.org/10.5194/bg-7-3289-2010.

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Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research initiated in the past several years have addressed the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or winds, may also have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.

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Corbett, D. R. "Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary." Biogeosciences Discussions 7, no. 2 (April 16, 2010): 2767–98. http://dx.doi.org/10.5194/bgd-7-2767-2010.

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Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research studies initiated in the past several years have addressed the complex nutrient cycles in this system. Most of this research, however, is concerned with the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or wind-generated waves, may have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in porewater and bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.

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Callegary, James B., Laura M. Norman, Christopher J. Eastoe, Joel B. Sankey, and Ann Youberg. "Preliminary Assessment of Carbon and Nitrogen Sequestration Potential of Wildfire-Derived Sediments Stored by Erosion Control Structures in Forest Ecosystems, Southwest USA." Air, Soil and Water Research 14 (January 2021): 117862212110017. http://dx.doi.org/10.1177/11786221211001768.

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The role of pyrogenic carbon (PyC) in the global carbon cycle is still incompletely characterized. Much work has been done to characterize PyC on landforms and in soils where it originates or in “terminal” reservoirs such as marine sediments. Less is known about intermediate reservoirs such as streams and rivers, and few studies have characterized hillslope and in-stream erosion control structures (ECS) designed to capture soils and sediments destabilized by wildfire. In this preliminary study, organic carbon (OC), total nitrogen (N), and stable isotope parameters, δ13C and δ15N, were compared to assess opportunities for carbon and nitrogen sequestration in postwildfire sediments (fluvents) deposited upgradient of ECS in ephemeral- and intermittent-stream channels. The variability of OC, N, δ13C, and δ15N were analyzed in conjunction with fire history, age of captured sediments, topographic position, and land cover. Comparison of samples in 2 watersheds indicates higher OC and N in ECS with more recently captured sediments located downstream of areas with higher burn severity. This is likely a consequence of (1) higher burn severity causing greater runoff, erosion, and transport of OC (organic matter) to ECS and (2) greater cumulative loss of OC and N in older sediments stored behind older ECS. In addition, C/N, δ13C, and δ15N results suggest that organic matter in sediments stored at older ECS are enriched in microbially processed biomass relative to those at newer ECS. We conservatively estimated the potential mean annual capture of OC by ECS, using values from the watershed with lower levels of OC, to be 3 to 4 metric tons, with a total potential storage of 293 to 368 metric tons in a watershed of 7.7 km2 and total area of 2000 ECS estimated at 2.6 ha (203-255 metric tons/ha). We extrapolated the OC results to the regional level (southwest USA) to estimate the potential for carbon sequestration using these practices. We estimated a potential of 0.01 Pg, which is significant in terms of ecosystem services and regional efforts to promote carbon storage.

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Guo, Yanyan, Cui Lai, Guangming Zeng, Jilai Gong, Chang Su, Chunping Yang, and Piao Xu. "Sequestration of HCHs and DDTs in sediments in Dongting Lake of China with multiwalled carbon nanotubes: implication for in situ sequestration." Environmental Science and Pollution Research 24, no. 8 (January 26, 2017): 7726–39. http://dx.doi.org/10.1007/s11356-017-8468-9.

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39

Haynes, Kelly, Tanja A. Hofmann, Cindy J. Smith, Andrew S. Ball, Graham J. C. Underwood, and A. Mark Osborn. "Diatom-Derived Carbohydrates as Factors Affecting Bacterial Community Composition in Estuarine Sediments." Applied and Environmental Microbiology 73, no. 19 (August 3, 2007): 6112–24. http://dx.doi.org/10.1128/aem.00551-07.

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ABSTRACT Microphytobenthic biofilms in estuaries, dominated by epipelic diatoms, are sites of high primary productivity. These diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides and glycoproteins, providing a substantial pool of organic carbon available to heterotrophs within the sediment. In this study, sediment slurry microcosms were enriched with either colloidal carbohydrates or colloidal EPS (cEPS) or left unamended. Over 10 days, the fate of these carbohydrates and changes in β-glucosidase activity were monitored. Terminal restriction fragment length polymorphism (T-RFLP), DNA sequencing, and quantitative PCR (Q-PCR) analysis of 16S rRNA sequences were used to determine whether sediment bacterial communities exhibited compositional shifts in response to the different available carbon sources. Initial heterotrophic activity led to reductions in carbohydrate concentrations in all three microcosms from day 0 to day 2, with some increases in β-glucosidase activity. During this period, treatment-specific shifts in bacterial community composition were not observed. However, by days 4 and 10, the bacterial community in the cEPS-enriched sediment diverged from those in colloid-enriched and unamended sediments, with Q-PCR analysis showing elevated bacterial numbers in the cEPS-enriched sediment at day 4. Community shifts were attributed to changes in cEPS concentrations and increased β-glucosidase activity. T-RFLP and sequencing analyses suggested that this shift was not due to a total community response but rather to large increases in the relative abundance of members of the γ-proteobacteria, particularly Acinetobacter-related bacteria. These experiments suggest that taxon- and substrate-specific responses within the bacterial community are involved in the degradation of diatom-derived extracellular carbohydrates.

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Megens, Luc, Johannes Van Der Plicht, and Jan W. De Leeuw. "Molecular, Radioactive and Stable Carbon Isotope Characterization of Estuarine Particulate Organic Matter." Radiocarbon 40, no. 2 (1997): 985–90. http://dx.doi.org/10.1017/s0033822200018956.

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Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger than the bulk sample and have a somewhat higher δ13C value. Lipids and the final residue are considerably older and have lower δ13C values. The final residue, ca. 17% of the total carbon, consists mainly of aliphatic macromolecules that could be derived from algae or terrestrial plants. The δ13C value points to a marine origin.

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Arienzo, Michele, Francesco Bolinesi, Giuseppe Aiello, Diana Barra, Carlo Donadio, Corrado Stanislao, Luciano Ferrara, et al. "The Environmental Assessment of an Estuarine Transitional Environment, Southern Italy." Journal of Marine Science and Engineering 8, no. 9 (August 19, 2020): 628. http://dx.doi.org/10.3390/jmse8090628.

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A multidisciplinary survey was carried out on the quality of water and sediments of the estuary of the Sele river, an important tributary of the Tyrrhenian Sea, to assess anthropogenic pressures and natural variability. Nine sediment sites were monitored and analyzed for granulometry, morphoscopy, benthic foraminifera and ostracod assemblages, heavy metals, and polycyclic aromatic hydrocarbons. Surface water was assayed for ionic composition and phytoplankton biomass. Total organic carbon (TOC) and total nitrogen (TN) in sediments were higher in the inner part of the estuary (IE), up to 12.7 and 0.7% because of anthropic influence. In waters, N-NH4, N-NO3, and Ptot. were high, with loads of Ptot in IE exceeding ~fourfold the limit. Here, it was also observed that the highest primary production was Chl-a, 95.70 µg/L, with cryptophytes, 37.6%, and diatoms, 33.8%, being the main phytoplanktonic groups. The hierarchical analysis split the estuary into two areas, with marked differences in anthropic pollution. Waters were classified as poor–bad level with respect to the content of nutrients. Sedimentological assay reveals littoral erosion and poor supply of river sandy sediments. The erosion environment is confirmed by the presence of meiobenthic recent marine forms intrusion inside the river. All these data reveal the fragility of the estuary and the need of urgent remediation actions.

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42

He, B., M. Dai, W. Huang, Q. Liu, H. Chen, and L. Xu. "Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions." Biogeosciences 7, no. 10 (October 28, 2010): 3343–62. http://dx.doi.org/10.5194/bg-7-3343-2010.

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Abstract. Organic matter in surface sediments from the upper reach of the Pearl River Estuary and Lingdingyang Bay, as well as the adjacent northern South China Sea shelf was characterized using a variety of techniques, including elemental (C and N) ratio, bulk stable organic carbon isotopic composition (δ13C), and carbohydrate composition analyses. Total organic carbon (TOC) content was 1.21±0.45% in the upper reach, down to 1.00±0.22% in Lingdingyang Bay and to 0.80±0.10% on the inner shelf and 0.58±0.06% on the outer shelf. δ13C values ranged from −25.1‰ to −21.3‰ in Lingdingyang Bay and the South China Sea shelf, with a trend of enrichment seawards. The spatial trend in C/N ratios mirrored that of δ13C, with a substantial decrease in C/N ratio offshore. Total carbohydrate yields ranged from 22.1 to 26.7 mg (100 mg OC)−1, and typically followed TOC concentrations in the estuarine and shelf sediments. Total neutral sugars, as detected by the nine major monosaccharides (lyxose, rhamnose, ribose, arabinose, fucose, xylose, galactose, mannose, and glucose), were between 4.0 and 18.6 mg (100 mg OC)−1 in the same sediments, suggesting that significant amounts of carbohydrates were not neutral aldoses. Using a two end-member mixing model based on δ13C values and C/N ratios, we estimated that the terrestrial organic carbon contribution to the surface sediment TOC was ca. 78±11% for Lingdingyang Bay, 34±4% for the inner shelf, and 5.5±1% for the outer shelf. The molecular composition of the carbohydrate in the surface sediments also suggested that the inner estuary was rich in terrestrially derived carbohydrates but that their contribution decreased offshore. A relatively high abundance of deoxyhexoses in the estuary and shelf indicated a considerable bacterial source of these carbohydrates, implying that sediment organic matter had undergone extensive degradation and/or transformation during transport. Sediment budget based on calculated regional accumulation rates showed that only ~50% of the influxes of terrestrial organic carbon were accumulated in the estuary. This relatively low accumulation efficiency of terrestrial organic matter as compared to the total suspended solids (accumulation efficiency ~73%) suggested significant degradation of the terrestrial organic carbon within the estuarine system after its discharge from the river. This study demonstrated that the combination of the bulk organic matter properties together with the isotopic composition and molecular-level carbohydrate compositions can be an efficient way to track down the source and fate of organic matter in highly dynamic estuarine and coastal systems. The predominance of terrestrially originated organic matter in the sediment and its generally low accumulation efficiency within the estuary is not surprising, and yet it may have important implications in light of the heavy anthropogenic discharges into the Pearl River Estuary during the past thirty years.

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Woulds, Clare, Steven Bouillon, Gregory L. Cowie, Emily Drake, Jack J. Middelburg, and Ursula Witte. "Patterns of carbon processing at the seafloor: the role of faunal and microbial communities in moderating carbon flows." Biogeosciences 13, no. 15 (August 4, 2016): 4343–57. http://dx.doi.org/10.5194/bg-13-4343-2016.

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Abstract. Marine sediments, particularly those located in estuarine and coastal zones, are key locations for the burial of organic carbon (C). However, organic C delivered to the sediment is subjected to a range of biological C-cycling processes, the rates and relative importance of which vary markedly between sites, and which are thus difficult to predict. In this study, stable isotope tracer experiments were used to quantify the processing of C by microbial and faunal communities in two contrasting Scottish estuarine sites: a subtidal, organic C rich site in Loch Etive with cohesive fine-grained sediment, and an intertidal, organic C poor site on an Ythan estuary sand flat with coarse-grained permeable sediments. In both experiments, sediment cores were recovered and amended with 13C labelled phytodetritus to quantify whole community respiration of the added C and to trace the isotope label into faunal and bacterial biomass. Similar respiration rates were found in Loch Etive and on the Ythan sand flat (0.64 ± 0.04 and 0.63 ± 0.12 mg C m−2h−1, respectively), which we attribute to the experiments being conducted at the same temperature. Faunal uptake of added C over the whole experiment was markedly greater in Loch Etive (204 ± 72 mg C m−2) than on the Ythan sand flat (0.96 ± 0.3 mg C m−2), and this difference was driven by a difference in both faunal biomass and activity. Conversely, bacterial C uptake over the whole experiment in Loch Etive was much lower than that on the Ythan sand flat (1.80 ± 1.66 and 127 ± 89 mg C m−2, respectively). This was not driven by differences in biomass, indicating that the bacterial community in the permeable Ythan sediments was particularly active, being responsible for 48 ± 18 % of total biologically processed C. This type of biological C processing appears to be favoured in permeable sediments. The total amount of biologically processed C was greatest in Loch Etive, largely due to greater faunal C uptake, which was in turn a result of higher faunal biomass. When comparing results from this study with a wide range of previously published isotope tracing experiments, we found a strong correlation between total benthic biomass (fauna plus bacteria) and total biological C processing rates. Therefore, we suggest that the total C-cycling capacity of benthic environments is primarily determined by total biomass.

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Chuan, Chee Hoe, John Barry Gallagher, Swee Theng Chew, and M. Zanuri Norlaila Binti. "Blue carbon sequestration dynamics within tropical seagrass sediments: long-term incubations for changes over climatic scales." Marine and Freshwater Research 71, no. 8 (2020): 892. http://dx.doi.org/10.1071/mf19119.

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Determination of blue carbon sequestration in seagrass sediments over climatic time scales (>100 years) relies on several assumptions, including no loss of particulate organic carbon (POC) after 1–2 years, tight coupling between POC loss and CO2 emissions, no dissolution of carbonates, and removal of the recalcitrant black carbon (BC) contribution. We tested these assumptions via 500-day anoxic decomposition and mineralisation experiments to capture centennial parameter decay dynamics from two sediment horizons robustly dated as 2 and 18 years old. No loss of BC was detected, and decay of POC was best described for both horizons by near-identical reactivity continuum models. The models predicted average losses of 49 and 51% after 100 years of burial for the surface and 20–22-cm horizons respectively. However, the loss rate of POC was far greater than the release rate of CO2, even after accounting for CO2 from particulate inorganic carbon (PIC) production, possibly as siderite. The deficit could not be attributed to dissolved organic carbon or dark CO2 fixation. Instead, evidence based on δ13CO2, acidity and lack of sulfate reduction suggested methanogenesis. The results indicated the importance of centennial losses of POC and PIC precipitation and possibly methanogenesis in estimating carbon sequestration rates.

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Gerritse, Robert G. "Sulphur, organic carbon and iron relationships in estuarine and freshwater sediments: effects of sedimentation rate." Applied Geochemistry 14, no. 1 (January 1999): 41–52. http://dx.doi.org/10.1016/s0883-2927(98)00041-9.

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Zhao, B., P. Yao, T. S. Bianchi, M. R. Shields, X. Q. Cui, X. W. Zhang, X. Y. Huang, C. Schröeder, J. Zhao, and Z. G. Yu. "The Role of Reactive Iron in the Preservation of Terrestrial Organic Carbon in Estuarine Sediments." Journal of Geophysical Research: Biogeosciences 123, no. 12 (December 2018): 3556–69. http://dx.doi.org/10.1029/2018jg004649.

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Lazar, Cassandre Sara, Brett J. Baker, Kiley Seitz, Andrew S. Hyde, Gregory J. Dick, Kai-Uwe Hinrichs, and Andreas P. Teske. "Genomic evidence for distinct carbon substrate preferences and ecological niches of Bathyarchaeota in estuarine sediments." Environmental Microbiology 18, no. 4 (January 18, 2016): 1200–1211. http://dx.doi.org/10.1111/1462-2920.13142.

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Ren, Liang-Liang, Min Jiang, Ling-Ban Wang, Yi-Jian Zhu, Zhi Li, Chang-Yu Sun, and Guang-Jin Chen. "Gas hydrate exploitation and carbon dioxide sequestration under maintaining the stiffness of hydrate-bearing sediments." Energy 194 (March 2020): 116869. http://dx.doi.org/10.1016/j.energy.2019.116869.

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Anderson, N. J., A. J. Heathcote, and D. R. Engstrom. "Anthropogenic alteration of nutrient supply increases the global freshwater carbon sink." Science Advances 6, no. 16 (April 2020): eaaw2145. http://dx.doi.org/10.1126/sciadv.aaw2145.

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Lakes have a disproportionate effect on the global carbon (C) cycle relative to their area, mediating C transfer from land to atmosphere, and burying organic-C in their sediments. The magnitude and temporal variability of C burial is, however, poorly constrained, and the degree to which humans have influenced lake C cycling through landscape alteration has not been systematically assessed. Here, we report global and biome specific trajectories of lake C sequestration based on 516 lakes and show that some lake C burial rates (i.e., those in tropical forest and grassland biomes) have quadrupled over the last 100 years. Global lake C-sequestration (~0.12 Pg year−1) has increased by ~72 Tg year−1 since 1900, offsetting 20% of annual CO2 freshwater emissions rising to ~30% if reservoirs are included and contributing to the residual continental C sink. Nutrient availability explains ~70% of the observed increase, while rising temperatures have a minimal effect.

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Kadlec, V., O. Holubík, E. Procházková, J. Urbanová, and M. Tippl. "Soil organic carbon dynamics and its influence on the soil erodibility factor." Soil and Water Research 7, No. 3 (July 10, 2012): 97–108. http://dx.doi.org/10.17221/3/2012-swr.

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The effect of erosion and erosion control measures on changes in the amount of organic matter in soil was studied. We investigated the influence of organic matter inputs into the soil on surface runoff, soil erosion and soil erodibility (K-factor), including the monitoring of carbon dynamics, as a result of torrential rains. The research was conducted on experimental plots in Třebsín site. Erosion leads to soil carbon loss and subsequently to increasing concentrations of carbon in sediments (enrichment ratio). We can conclude from the results that the input of organic matter into the soil (especially farmyard manure) significantly contributes to a decrease in surface runoff and soil loss and also to a reduction of carbon leaching into sediments; so it contributes to carbon sequestration into the soil.

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Journal articles on the topic 'Estuarine sediments. Carbon sequestration'

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