Journal articles: 'Coastal carbon cycling'

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Fennel, Katja, Simone Alin, Leticia Barbero, Wiley Evans, Timothée Bourgeois, Sarah Cooley, John Dunne, et al. "Carbon cycling in the North American coastal ocean: a synthesis." Biogeosciences 16, no. 6 (March 27, 2019): 1281–304. http://dx.doi.org/10.5194/bg-16-1281-2019.

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Abstract. A quantification of carbon fluxes in the coastal ocean and across its boundaries with the atmosphere, land, and the open ocean is important for assessing the current state and projecting future trends in ocean carbon uptake and coastal ocean acidification, but this is currently a missing component of global carbon budgeting. This synthesis reviews recent progress in characterizing these carbon fluxes for the North American coastal ocean. Several observing networks and high-resolution regional models are now available. Recent efforts have focused primarily on quantifying the net air–sea exchange of carbon dioxide (CO2). Some studies have estimated other key fluxes, such as the exchange of organic and inorganic carbon between shelves and the open ocean. Available estimates of air–sea CO2 flux, informed by more than a decade of observations, indicate that the North American Exclusive Economic Zone (EEZ) acts as a sink of 160±80 Tg C yr−1, although this flux is not well constrained. The Arctic and sub-Arctic, mid-latitude Atlantic, and mid-latitude Pacific portions of the EEZ account for 104, 62, and −3.7 Tg C yr−1, respectively, while making up 51 %, 25 %, and 24 % of the total area, respectively. Combining the net uptake of 160±80 Tg C yr−1 with an estimated carbon input from land of 106±30 Tg C yr−1 minus an estimated burial of 65±55 Tg C yr−1 and an estimated accumulation of dissolved carbon in EEZ waters of 50±25 Tg C yr−1 implies a carbon export of 151±105 Tg C yr−1 to the open ocean. The increasing concentration of inorganic carbon in coastal and open-ocean waters leads to ocean acidification. As a result, conditions favoring the dissolution of calcium carbonate occur regularly in subsurface coastal waters in the Arctic, which are naturally prone to low pH, and the North Pacific, where upwelling of deep, carbon-rich waters has intensified. Expanded monitoring and extension of existing model capabilities are required to provide more reliable coastal carbon budgets, projections of future states of the coastal ocean, and quantification of anthropogenic carbon contributions.

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Mackenzie, F. T., A. Lerman, and A. J. Andersson. "Past and present of sediment and carbon biogeochemical cycling models." Biogeosciences 1, no. 1 (August 20, 2004): 11–32. http://dx.doi.org/10.5194/bg-1-11-2004.

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Abstract. The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification that still occurs in this region. Furthermore, evidence from the inorganic carbon cycle indicates that deposition and net storage of CaCO3 in sediments exceed inflow of inorganic carbon from land and produce CO2 emissions to the atmosphere. In the shallow-water coastal zone, increase in atmospheric CO2 during the last 300 years of industrial time may have reduced the rate of calcification, and continuation of this trend is an issue of serious environmental concern in the global carbon balance.

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Mackenzie, F. T., A. Lerman, and A. J. Andersson. "Past and present of sediment and carbon biogeochemical cycling models." Biogeosciences Discussions 1, no. 1 (May 24, 2004): 27–85. http://dx.doi.org/10.5194/bgd-1-27-2004.

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Abstract. The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification that still occurs in this region. Furthermore, evidence from the inorganic carbon cycle indicates that deposition and net storage of CaCO3 in sediments exceed inflow of inorganic carbon from land and produce CO2 emissions to the atmosphere. In the shallow-water coastal zone, increase in atmospheric CO2 during the last 300 years of industrial time may have reduced the rate of calcification, and continuation of this trend is an issue of serious environmental concern in the global carbon balance.

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Banerjee, Kakoli, Abhijit Mitra, and Sebastián Villasante. "Carbon Cycling in Mangrove Ecosystem of Western Bay of Bengal (India)." Sustainability 13, no. 12 (June 15, 2021): 6740. http://dx.doi.org/10.3390/su13126740.

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Carbon cycling in the mangrove ecosystem is one of the important processes determining the potential of coastal vegetation (mangroves), sediment, and adjoining waters to carbon absorption. This paper investigates the carbon storage capacity of five dominant mangrove species (Avicenia marina, Avicenia officinalis, Excoecaria agallocha, Rhizophora mucronata, and Xylocarpous granatum) on the east coast of the Indian mangrove along with the role they play in the carbon cycling phenomenon. Soil and water parameters were analyzed simultaneously with Above Ground Biomass (AGB) and Above Ground Carbon (AGC) values for 10 selected stations along. The total carbon (TC) calculated from the study area varied from 51.35 ± 6.77 to 322.47 ± 110.79 tons per hectare with a mean total carbon of 117.89 ± 28.90 and 432.64 ± 106.05 tons of carbon dioxide equivalent (CO2e). The alarm of the Intergovernmental Panel on Climate Change for reducing carbon emissions has been addressed by calculating the amount of carbon stored in biotic (mangroves) and abiotic (soil and water) compartments. This paper focuses on the technical investigations on the factors that control the carbon cycling process in mangroves. This blue carbon will help policymakers to develop a sustainable relationship between marine resource management and coastal inhabitants so that carbon trading markets can be developed, and the ecosystem is balanced.

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Filbee-Dexter, Karen, Colette J. Feehan, Dan A. Smale, Kira A. Krumhansl, Skye Augustine, Florian de Bettignies, Michael T. Burrows, et al. "Kelp carbon sink potential decreases with warming due to accelerating decomposition." PLOS Biology 20, no. 8 (August 4, 2022): e3001702. http://dx.doi.org/10.1371/journal.pbio.3001702.

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Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.

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Alongi, Daniel Michael. "Impacts of Climate Change on Blue Carbon Stocks and Fluxes in Mangrove Forests." Forests 13, no. 2 (January 19, 2022): 149. http://dx.doi.org/10.3390/f13020149.

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Mangroves store blue carbon (693 Mg CORG ha−1) disproportionate to their small area, mainly (74%) in deep soil horizons. Global stock estimates for mangroves (5.23–8.63 Pg CORG) are equivalent to 15–24% of those in the tropical coastal ocean. Carbon burial in mangrove soils averages 184 g CORG m−2 a−1 with global estimates (9.6–15.8 Tg CORG a−1) reflecting their importance in carbon sequestration. Extreme weather events result in carbon stock losses and declines in carbon cycling and export. Increased frequency and ferocity of storms result in increasingly negative responses with increasing strength. Increasing temperatures result in increases in carbon stocks and cycling up to a critical threshold, while positive/negative responses will likely result from increases/decreases in rainfall. Forest responses to sea-level rise (SLR) and rising CO2 are species- and site-specific and complex due to interactive effects with other drivers (e.g., temperature, salinity). The SLR critical threshold is ≈ 6 mm a−1 indicating survival only under very low-low CO2 emissions scenarios. Under low coastal squeeze, landward migration could result in sequestration and CO2 losses of 1.5 and −1.1 Pg C with net stock gains and losses (−0.3 to +0.5 Pg C) and CO2 losses (−3.4 Pg) under high coastal squeeze.

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Zhu, Zhongbin, Robert C. Aller, and John Mak. "Stable carbon isotope cycling in mobile coastal muds of Amapá, Brazil." Continental Shelf Research 22, no. 15 (October 2002): 2065–79. http://dx.doi.org/10.1016/s0278-4343(02)00071-7.

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8

Rowe, Gilbert T., and Ann P. McNichol. "Carbon cycling in coastal sediments: Estimating remineralization in Buzzards Bay, Massachusetts." Geochimica et Cosmochimica Acta 55, no. 10 (October 1991): 2989–91. http://dx.doi.org/10.1016/0016-7037(91)90465-h.

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9

Alongi, Daniel M., and Sandip K. Mukhopadhyay. "Contribution of mangroves to coastal carbon cycling in low latitude seas." Agricultural and Forest Meteorology 213 (November 2015): 266–72. http://dx.doi.org/10.1016/j.agrformet.2014.10.005.

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Gao, Yang, Tiantian Yang, Yafeng Wang, and Guirui Yu. "Fate of river‐transported carbon in china: implications for carbon cycling in coastal ecosystems." Ecosystem Health and Sustainability 3, no. 3 (March 2017): e01265. http://dx.doi.org/10.1002/ehs2.1265.

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11

Barr, Jordan G., Tiffany G. Troxler, and Raymond G. Najjar. "Understanding Coastal Carbon Cycling by Linking Top-Down and Bottom-Up Approaches." Eos, Transactions American Geophysical Union 95, no. 35 (September 2, 2014): 315. http://dx.doi.org/10.1002/2014eo350004.

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12

Alongi, Daniel M. "Carbon Cycling in the World’s Mangrove Ecosystems Revisited: Significance of Non-Steady State Diagenesis and Subsurface Linkages between the Forest Floor and the Coastal Ocean." Forests 11, no. 9 (September 10, 2020): 977. http://dx.doi.org/10.3390/f11090977.

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Carbon cycling within the deep mangrove forest floor is unique compared to other marine ecosystems with organic carbon input, mineralization, burial, and advective and groundwater export pathways being in non-steady-state, often oscillating in synchrony with tides, plant uptake, and release/uptake via roots and other edaphic factors in a highly dynamic and harsh environment. Rates of soil organic carbon (CORG) mineralization and belowground CORG stocks are high, with rapid diagenesis throughout the deep (>1 m) soil horizon. Pocketed with cracks, fissures, extensive roots, burrows, tubes, and drainage channels through which tidal waters percolate and drain, the forest floor sustains non-steady-state diagenesis of the soil CORG, in which decomposition processes at the soil surface are distinct from those in deeper soils. Aerobic respiration occurs within the upper 2 mm of the soil surface and within biogenic structures. On average, carbon respiration across the surface soil-air/water interface (104 mmol C m−2 d−1) equates to only 25% of the total carbon mineralized within the entire soil horizon, as nearly all respired carbon (569 mmol C m−2 d−1) is released in a dissolved form via advective porewater exchange and/or lateral transport and subsurface tidal pumping to adjacent tidal waters. A carbon budget for the world’s mangrove ecosystems indicates that subsurface respiration is the second-largest respiratory flux after canopy respiration. Dissolved carbon release is sufficient to oversaturate water-column pCO2, causing tropical coastal waters to be a source of CO2 to the atmosphere. Mangrove dissolved inorganic carbon (DIC) discharge contributes nearly 60% of DIC and 27% of dissolved organic carbon (DOC) discharge from the world’s low latitude rivers to the tropical coastal ocean. Mangroves inhabit only 0.3% of the global coastal ocean area but contribute 55% of air-sea exchange, 14% of CORG burial, 28% of DIC export, and 13% of DOC + particulate organic matter (POC) export from the world’s coastal wetlands and estuaries to the atmosphere and global coastal ocean.

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Glud, Ronnie N., and Middelboe Mathias. "Virus and bacteria dynamics of a coastal sediment: Implication for benthic carbon cycling." Limnology and Oceanography 49, no. 6 (November 2004): 2073–81. http://dx.doi.org/10.4319/lo.2004.49.6.2073.

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Burden, A., R. A. Garbutt, C. D. Evans, D. L. Jones, and D. M. Cooper. "Carbon sequestration and biogeochemical cycling in a saltmarsh subject to coastal managed realignment." Estuarine, Coastal and Shelf Science 120 (March 2013): 12–20. http://dx.doi.org/10.1016/j.ecss.2013.01.014.

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Riedel, Andrea, Christine Michel, Michel Gosselin, and Bernard LeBlanc. "Winter–spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean." Journal of Marine Systems 74, no. 3-4 (December 2008): 918–32. http://dx.doi.org/10.1016/j.jmarsys.2008.01.003.

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Tomaszewski, E. J., E. K. Coward, and D. L. Sparks. "Ionic Strength and Species Drive Iron–Carbon Adsorption Dynamics: Implications for Carbon Cycling in Future Coastal Environments." Environmental Science & Technology Letters 8, no. 8 (July 19, 2021): 719–24. http://dx.doi.org/10.1021/acs.estlett.1c00432.

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Semiletov, I. P., N. E. Shakhova, I. I. Pipko, S. P. Pugach, A. N. Charkin, O. V. Dudarev, D. A. Kosmach, and S. Nishino. "Space-time dynamics of carbon stocks and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay of the Laptev Sea." Biogeosciences Discussions 10, no. 2 (February 6, 2013): 2159–204. http://dx.doi.org/10.5194/bgd-10-2159-2013.

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Abstract. This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) by studying the inter-annual, seasonal, and meso-scale variability of carbon stocks and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO2) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, coastal erosion and river discharge serve as predominant drivers of the organic carbon (OC) cycle, determining OC input and transformation, dynamics of nutrients, carbon stocks in the water column, and atmospheric emissions of CO2.

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Shruthi, PK, Ammini Parvathi, Angia Sriram Pradeep Ram, Shyla Hafza, Jose K. Albin, Erathodi Rajagopalan Vignesh, Jaleel Abdul, and Telesphore Sime-Ngando. "Contrasting Impact of Viral Activity on Prokaryotic Populations in the Coastal and Offshore Regions of the Eastern Arabian Sea." Diversity 14, no. 3 (March 21, 2022): 230. http://dx.doi.org/10.3390/d14030230.

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Viral processes in the coastal and offshore regions of the Eastern Arabian Sea (west coast of India) and their contribution of viral lysis to the organic carbon and nitrogen pool was examined. Water samples were collected during the southwest monsoon season at different depths (up to 1000 m) from four transects, with each transect consisting of two sampling points (S1–S8). Abundances of viruses and prokaryotes together with viral mediated prokaryotic mortality (up to 49.7%) were significantly (p < 0.001) higher in eutrophic coastal stations, whereas high percent lysogeny (up to 93%) was observed in the offshore regions. High viral-mediated carbon (Mean ± SD = 67.47 ± 2.0 μM C L−1 d−1) and nitrogen (Mean ± SD = 13.49 ± 14.0 μM N L−1 d−1) release was evident in the surface coastal waters compared to offshore regions. The percentage contributions of carbon and nitrogen released by viral lysis to the total dissolved organic carbon and nitrogen pool were estimated to be 7.4% and 3.9%, respectively, in the coastal surface waters. Our findings suggest that the contribution of viral lysis to DOM production through viral shunt could be crucial for the cycling of major biogeochemical elements and functioning of the studied tropical ecosystem.

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Voss, Maren, Hermann W. Bange, Joachim W. Dippner, Jack J. Middelburg, Joseph P. Montoya, and Bess Ward. "The marine nitrogen cycle: recent discoveries, uncertainties and the potential relevance of climate change." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1621 (July 5, 2013): 20130121. http://dx.doi.org/10.1098/rstb.2013.0121.

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The ocean's nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation, assimilation, nitrification, anammox and denitrification. Dinitrogen is the most abundant form of nitrogen in sea water but only accessible by nitrogen-fixing microbes. Denitrification and nitrification are both regulated by oxygen concentrations and potentially produce nitrous oxide (N 2 O), a climate-relevant atmospheric trace gas. The world's oceans, including the coastal areas and upwelling areas, contribute about 30 per cent to the atmospheric N 2 O budget and are, therefore, a major source of this gas to the atmosphere. Human activities now add more nitrogen to the environment than is naturally fixed. More than half of the nitrogen reaches the coastal ocean via river input and atmospheric deposition, of which the latter affects even remote oceanic regions. A nitrogen budget for the coastal and open ocean, where inputs and outputs match rather well, is presented. Furthermore, predicted climate change will impact the expansion of the oceans' oxygen minimum zones, the productivity of surface waters and presumably other microbial processes, with unpredictable consequences for the cycling of nitrogen. Nitrogen cycling is closely intertwined with that of carbon, phosphorous and other biologically important elements via biological stoichiometric requirements. This linkage implies that human alterations of nitrogen cycling are likely to have major consequences for other biogeochemical processes and ecosystem functions and services.

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Vargas, CA, and HE González. "Plankton community structure and carbon cycling in a coastal upwelling system. II. Microheterotrophic pathway." Aquatic Microbial Ecology 34 (2004): 165–80. http://dx.doi.org/10.3354/ame034165.

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Anderson, N. J., M. J. Leng, C. L. Osburn, S. C. Fritz, A. C. Law, and S. McGowan. "A landscape perspective of Holocene organic carbon cycling in coastal SW Greenland lake-catchments." Quaternary Science Reviews 202 (December 2018): 98–108. http://dx.doi.org/10.1016/j.quascirev.2018.09.006.

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Butler, James H., John E. Pequegnat, Louis I. Gordon, and Ronald D. Jones. "Cycling of methane, carbon monoxide, nitrous oxide, and hydroxylamine in a meromictic, coastal lagoon." Estuarine, Coastal and Shelf Science 27, no. 2 (August 1988): 181–203. http://dx.doi.org/10.1016/0272-7714(88)90089-3.

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23

Ward, Melissa A., Tessa M. Hill, Chelsey Souza, Tessa Filipczyk, Aurora M. Ricart, Sarah Merolla, Lena R. Capece, et al. "Blue carbon stocks and exchanges along the California coast." Biogeosciences 18, no. 16 (August 18, 2021): 4717–32. http://dx.doi.org/10.5194/bg-18-4717-2021.

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Abstract. Salt marshes and seagrass meadows can sequester and store high quantities of organic carbon (OC) in their sediments relative to other marine and terrestrial habitats. Assessing carbon stocks, carbon sources, and the transfer of carbon between habitats within coastal seascapes are each integral in identifying the role of blue carbon habitats in coastal carbon cycling. Here, we quantified carbon stocks, sources, and exchanges in seagrass meadows, salt marshes, and unvegetated sediments in six bays along the California coast. In the top 20 cm of sediment, the salt marshes contained approximately twice as much OC as seagrass meadows did, 4.92 ± 0.36 kg OC m−2 compared to 2.20 ± 0.24 kg OC m−2, respectively. Both salt marsh and seagrass sediment carbon stocks were higher than previous estimates from this region but lower than global and US-wide averages, respectively. Seagrass-derived carbon was deposited annually into adjacent marshes during fall seagrass senescence. However, isotope mixing models estimate that negligible amounts of this seagrass material were ultimately buried in underlying sediment. Rather, the vast majority of OC in sediment across sites was likely derived from planktonic/benthic diatoms and/or C3 salt marsh plants.

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Cui, Wen Fang, Chang Jing Shao, and Chun Ming Liu. "Corrosion Behavior of New Weathering Steel in the Environment Simulating Coastal Industrial Atmosphere." Advanced Materials Research 479-481 (February 2012): 322–26. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.322.

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The corrosion behavior of low carbon bainitic steel with Cu-P alloying in the environment simulating coastal industrial atmosphere was investigated by using dry-wet cycling corrosion test. 09CuPCrNi steel and low carbon bainitic steel without Cu-P alloying were used as comparative steels. The corrosion kinetics and electrochemical impedance spectra of the steels were measured, respectively. The morphologies of rust layers were observed by SEM and the phase constitutes of the rust layers were analyzed by XRD. Low carbon bainitic steel with Cu-P alloying behaves the lowest corrosion rate and the highest resistance of rust layer. Bainite microstructure is responsible for the uniform corrosion and the formation of dense rust layer. Cu-P alloying accelerates the transformation of gamma-FeOOH and Fe3O4 to thermodynamic stable phase alpha-FeOOH, which improves the protective effect of the rust layer.

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Dang, Duy Minh, Ben Macdonald, Sören Warneke, and Ian White. "Available carbon and nitrate increase greenhouse gas emissions from soils affected by salinity." Soil Research 55, no. 1 (2017): 47. http://dx.doi.org/10.1071/sr16010.

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Sea-level rise and saline water intrusion have caused a shortage of fresh water and affected agricultural areas globally. Besides inundation, the salinity could alter soil nitrogen and carbon cycling in coastal soils. To examine the effect of salinity, an incubation experiment was used to investigate soil nitrogen and carbon cycling from an acid sulfate soil and an alluvial soil with and without additional nitrogen and carbon sources. Four levels of saline solution of 0.03, 10, 16 and 21dSm–1 were used to submerge acid sulfate and alluvial soil samples in a 125-mL jar. The experimental jars were incubated in the dark at 25°C. Gas samples were collected over 4 weeks and analysed for nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4). The results showed that salinity significantly decreased N2O emissions from the acid sulfate soil but did not affect emissions from the alluvial soil. Addition of glucose and nitrate enhanced N2O production in both salt-affected soils. Emissions of CO2 were not different among the salinity treatments, whereas available carbon and nitrate promoted soil respiration. Changes in CH4 fluxes over the 4-week incubation were the same for both soils, and substrate addition did not affect emissions in either soil. The findings indicate that salinity has altered carbon and nitrogen cycles in the acid sulfate soil, and future fertiliser and crop management will need to account for the changed nutrient cycling caused by saline water intrusion and climate change.

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Holt, Jason, James Harle, Roger Proctor, Sylvain Michel, Mike Ashworth, Crispian Batstone, Icarus Allen, et al. "Modelling the global coastal ocean." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1890 (December 16, 2008): 939–51. http://dx.doi.org/10.1098/rsta.2008.0210.

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Shelf and coastal seas are regions of exceptionally high biological productivity, high rates of biogeochemical cycling and immense socio-economic importance. They are, however, poorly represented by the present generation of Earth system models, both in terms of resolution and process representation. Hence, these models cannot be used to elucidate the role of the coastal ocean in global biogeochemical cycles and the effects global change (both direct anthropogenic and climatic) are having on them. Here, we present a system for simulating all the coastal regions around the world (the Global Coastal Ocean Modelling System) in a systematic and practical fashion. It is based on automatically generating multiple nested model domains, using the Proudman Oceanographic Laboratory Coastal Ocean Modelling System coupled to the European Regional Seas Ecosystem Model. Preliminary results from the system are presented. These demonstrate the viability of the concept, and we discuss the prospects for using the system to explore key areas of global change in shelf seas, such as their role in the carbon cycle and climate change effects on fisheries.

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Lipson, D. A., D. Zona, T. K. Raab, F. Bozzolo, M. Mauritz, and W. C. Oechel. "Water table height and microtopography control biogeochemical cycling in an Arctic coastal tundra ecosystem." Biogeosciences Discussions 8, no. 4 (July 6, 2011): 6345–82. http://dx.doi.org/10.5194/bgd-8-6345-2011.

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Abstract. Drained thaw lake basins (DTLB) are the dominant land form of the Arctic coastal plain in northern Alaska. The presence of continuous permafrost prevents drainage and so water tables generally remain close to the soil surface, creating saturated, suboxic soil conditions. However, ice wedge polygons produce microtopographic variation in these landscapes, with raised areas such as polygon rims creating more oxic microenvironments. The peat soils in this ecosystem store large amounts of organic carbon which is vulnerable to loss as arctic regions continue to rapidly warm, and so there is great motivation to understand the controls over microbial activity in these complex landscapes. Here we report the effects of experimental flooding, along with seasonal and spatial variation in soil chemistry and microbial activity in a DTLB. The flooding treatment generally mirrored the effects of natural landscape variation in water table height due to microtopography. Areas in the flooded areas had lower dissolved oxygen, lower oxidation-reduction potential (ORP) and higher pH, as did lower elevation areas of the landscape. Similarly, soil pore water concentrations of dissolved ferric iron (Fe III), organic carbon, and aromatic compounds were higher in flooded and low elevation areas. Dissolved carbon dioxide (CO2) and methane (CH4) concentrations were higher in low elevation areas. In anaerobic laboratory incubations, more CH4 was produced by soils from low and flooded areas, whereas anaerobic CO2 production only responded to flooding in high elevation areas. Seasonal changes in the oxidation state of solid phase Fe minerals showed that significant dissimilatory Fe reduction occurred, especially in topographically low areas. This suite of results can all be attributed to the effect of water table on oxygen availability: flooded conditions promote anoxia, stimulating anaerobic processes, methanogenesis and Fe(III) reduction. Flooding also increased soil temperature, which might account for the higher N mineralization rates and dissolved P concentrations observed in flooded areas, though the latter could also have resulted from solubilization of Fe-P minerals under more reducing conditions. Overall, the results indicate that the microbial community is well-adapted for anaerobic respiration, in particular, dissimilatory Fe(III) reduction, and could have implications for some high Arctic areas where warming and flooding are likely consequences of climate change.

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Reader, H. E., and W. L. Miller. "Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight." Biogeosciences Discussions 9, no. 6 (June 14, 2012): 6947–85. http://dx.doi.org/10.5194/bgd-9-6947-2012.

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Abstract. The photochemical oxidation of oceanic dissolved organic carbon (DOC) to carbon monoxide (CO) and carbon dioxide (CO2) has been estimated to be a significant process with global photoproduction transforming petagrams of DOC to inorganic carbon annually. To further quantify the importance of these two photoproducts in coastal DOC cycling, 38 paired apparent quantum yield (AQY) spectra for CO and CO2 were determined at three locations along the coast of Georgia, USA over the course of one year. The AQY spectra for CO2 were considerably more varied than CO. CO AQY spectra exhibited a seasonal shift in spectrally integrated (260 nm–490 nm) AQY from higher efficiencies in the fall to less efficient photoproduction in the summer. While full-spectrum photoproduction rates for both products showed positive correlation with pre-irradiation UV-B sample absorption (i.e. chromophoric dissolved organic matter, CDOM) as expected, we found no correlation between AQY and CDOM for either product at any site. Molecular size, approximated with pre-irradiation spectral slope coefficients, and aromatic content, approximated by the specific ultraviolet absorption of the pre-irradiated samples, were also not correlated with AQY in either data set. The ratios of CO2 to CO photoproduction determined using both an AQY model and direct production comparisons were 23.2 ± 12.5 and 22.5 ± 9.0, respectively. Combined, both products represent a loss of 2.2 to 2.6 % of the DOC delivered to the estuaries and inner shelf of the South Atlantic Bight yearly, and 5 to 6 % of the total annual degassing of CO2 to the atmosphere. This result suggests that direct photochemical production of CO and CO2 is a small, yet significant contributor to both DOC cycling and CO2 gas exchange in this coastal system.

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Reader, H. E., and W. L. Miller. "Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight." Biogeosciences 9, no. 11 (November 6, 2012): 4279–94. http://dx.doi.org/10.5194/bg-9-4279-2012.

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Abstract. The photochemical oxidation of oceanic dissolved organic carbon (DOC) to carbon monoxide (CO) and carbon dioxide (CO2) has been estimated to be a significant process with global photoproduction transforming petagrams of DOC to inorganic carbon annually. To further quantify the importance of these two photoproducts in coastal DOC cycling, 38 paired apparent quantum yield (AQY) spectra for CO and CO2 were determined at three locations along the coast of Georgia, USA over the course of one year. The AQY spectra for CO2 were considerably more varied than CO. CO AQY spectra exhibited a seasonal shift in spectrally integrated (260 nm–490 nm) AQY from higher efficiencies in the autumn to less efficient photoproduction in the summer. While full-spectrum photoproduction rates for both products showed positive correlation with pre-irradiation UV-B sample absorption (i.e. chromophoric dissolved organic matter, CDOM) as expected, we found no correlation between AQY and CDOM for either product at any site. Molecular size, approximated with pre-irradiation spectral slope coefficients, and aromatic content, approximated by the specific ultraviolet absorption of the pre-irradiated samples, were also not correlated with AQY in either data set. The ratios of CO2 to CO photoproduction determined using both an AQY model and direct production comparisons were 23.2 ± 12.5 and 22.5 ± 9.0, respectively. Combined, both products represent a loss of 2.9 to 3.2% of the DOC delivered to the estuaries and inner shelf of the South Atlantic Bight yearly, and 6.4 to 7.3% of the total annual degassing of CO2 to the atmosphere. This result suggests that direct photochemical production of CO and CO2 is a small, yet significant contributor to both DOC cycling and CO2 gas exchange in this coastal system.

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Burdige, David J., and Christopher S. Martens. "Biogeochemical cycling in an organic-rich coastal marine basin: 10. The role of amino acids in sedimentary carbon and nitrogen cycling." Geochimica et Cosmochimica Acta 52, no. 6 (June 1988): 1571–84. http://dx.doi.org/10.1016/0016-7037(88)90226-8.

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Maxey, Johnathan Daniel, Neil David Hartstein, Aazani Mujahid, and Moritz Müller. "The influence of mesoscale climate drivers on hypoxia in a fjord-like deep coastal inlet and its potential implications regarding climate change: examining a decade of water quality data." Biogeosciences 19, no. 13 (July 4, 2022): 3131–50. http://dx.doi.org/10.5194/bg-19-3131-2022.

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Abstract. Deep coastal inlets are sites of high sedimentation and organic carbon deposition that account for 11 % of the world's organic carbon burial. Australasia's mid- to high-latitude regions have many such systems. It is important to understand the role of climate forcings in influencing hypoxia and organic matter cycling in these systems, but many such systems, especially in Australasia, remain poorly described. We analysed a decade of in situ water quality data from Macquarie Harbour, Tasmania, a deep coastal inlet with more than 180 000 t of organic carbon loading per annum. Monthly dissolved oxygen, total Kjeldahl nitrogen, dissolved organic carbon, and dissolved inorganic nitrogen concentrations were significantly affected by rainfall patterns. Increased rainfall was correlated to higher organic carbon and nitrogen loading, lower oxygen concentrations in deep basins, and greater oxygen concentrations in surface waters. Most notably, the Southern Annular Mode (SAM) significantly influenced oxygen distribution in the system. High river flow (associated with low SAM index values) impedes deep water renewal as the primary mechanism driving basin water hypoxia. Climate forecasting predicts increased winter rainfall and decreased summer rainfall, which may further exacerbate hypoxia in this system. Currently, Macquarie Harbour's basins experience frequent (up to 36 % of the time) and prolonged (up to 2 years) oxygen-poor conditions that may promote greenhouse gas (CH4, N2O) production altering the processing of organic matter entering the system. The increased winter rainfall predicted for the area will likely promote the increased spread and duration of hypoxia in the basins. Further understanding of these systems and how they respond to climate change will improve our estimates of future organic matter cycling (burial vs. export).

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Farías, L., C. Fernández, J. Faúndez, M. Cornejo, and M. E. Alcaman. "Chemolithoautotrophic production mediating the cycling of the greenhouse gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem." Biogeosciences 6, no. 12 (December 17, 2009): 3053–69. http://dx.doi.org/10.5194/bg-6-3053-2009.

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Abstract. The high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N2O and CH4 cycling associated with aerobic NH4+ (AAO) and CH4 oxidation (AMO). This is the case of the highly productive coastal upwelling area off central Chile (36° S), where we evaluated the importance of total chemolithoautotrophic vs. photoautotrophic production, the specific contributions of AAO and AMO to chemosynthesis and their role in gas cycling. Chemolithoautotrophy was studied at a time-series station during monthly (2007–2009) and seasonal cruises (January 2008, September 2008, January 2009) and was assessed in terms of the natural C isotopic ratio of particulate organic carbon (δ13POC), total and specific (associated with AAO and AMO) dark carbon assimilation (CA), and N2O and CH4 cycling experiments. At the oxycline, δ13POC averaged −22.2‰; this was significantly lighter compared to the surface (−19.7‰) and bottom layers (−20.7‰). Total integrated dark CA in the whole water column fluctuated between 19.4 and 2.924 mg C m−2 d−1, was higher during active upwelling, and contributed 0.7 to 49.7% of the total integrated autotrophic CA (photo plus chemoautotrophy), which ranged from 135 to 7.626 mg C m−2 d−1, and averaged 20.3% for the whole sampling period. Dark CA was reduced by 27 to 48% after adding a specific AAO inhibitor (ATU) and by 24 to 76% with GC7, a specific archaea inhibitor. This indicates that AAO and AMO microbes (most of them archaea) were performing dark CA through the oxidation of NH4+ and CH4. Net N2O cycling rates varied between 8.88 and 43 nM d−1, whereas net CH4 cycling rates ranged from −0.41 to −26.8 nM d−1. The addition of both ATU and GC7 reduced N2O accumulation and increased CH4 consumption, suggesting that AAO and AMO were responsible, in part, for the cycling of these gases. These findings show that chemically driven chemolithoautotrophy (with NH4+ and CH4 acting as electron donors) could be more important than previously thought in upwelling ecosystems, raising new questions concerning its relevance in the future ocean.

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Watson, Elizabeth Burke, Farzana I. Rahman, Andrea Woolfolk, Robert Meyer, Nicole Maher, Cathleen Wigand, and Andrew B. Gray. "High nutrient loads amplify carbon cycling across California and New York coastal wetlands but with ambiguous effects on marsh integrity and sustainability." PLOS ONE 17, no. 9 (September 9, 2022): e0273260. http://dx.doi.org/10.1371/journal.pone.0273260.

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Eutrophic conditions in estuaries are a globally important stressor to coastal ecosystems and have been suggested as a driver of coastal salt marsh loss. Potential mechanisms in marshes include disturbance caused by macroalgae accumulations, enhanced soil sulfide levels linked to high labile carbon inputs, accelerated decomposition, and declines in belowground biomass that contribute to edge instability, erosion, and slumping. However, results of fertilization studies have been mixed, and it is unclear the extent to which local environmental conditions, such as soil composition and nutrient profiles, help shape the response of salt marshes to nutrient exposure. In this study, we characterized belowground productivity and decomposition, organic matter mineralization rates, soil respiration, microbial biomass, soil humification, carbon and nitrogen inventories, nitrogen isotope ratios, and porewater profiles at high and low marsh elevations across eight marshes in four estuaries in California and New York that have strong contrasts in nutrient inputs. The higher nutrient load marshes were characterized by faster carbon turnover, with higher belowground production and decomposition and greater carbon dioxide efflux than lower nutrient load marshes. These patterns were robust across marshes of the Atlantic and Pacific coasts that varied in plant species composition, soil flooding patterns, and soil texture. Although impacts of eutrophic conditions on carbon cycling appeared clear, it was ambiguous whether high nutrient loads are causing negative effects on long-term marsh sustainability in terms of studied metrics. While high nutrient exposure marshes had high rates of decomposition and soil respiration rates, high nutrient exposure was also associated with increased belowground production, and reduced levels of sulfides, which should lead to greater marsh sustainability. While this study does not resolve the extent to which nutrient loads are negatively affecting these salt marshes, we do highlight functional differences between Atlantic and Pacific wetlands which may be useful for understanding coastal marsh health and integrity.

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Qian, ZHANG, LIU Bing-jie, YU Lu, WANG Rui-rui, ZHENG Hao, LUO Xian-xiang, and LI Feng-min. "Effects of biochar amendment on carbon and nitrogen cycling in coastal saline soils: A review." JOURNAL OF NATURAL RESOURCES 34, no. 12 (2019): 2529. http://dx.doi.org/10.31497/zrzyxb.20191204.

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Samui, Gautami, Runa Antony, and Meloth Thamban. "Chemical characteristics of hydrologically distinct cryoconite holes in coastal Antarctica." Annals of Glaciology 59, no. 77 (November 26, 2018): 69–76. http://dx.doi.org/10.1017/aog.2018.30.

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ABSTRACTCryoconite holes play a significant role in the nutrient cycling on glaciers and can be regarded as a storehouse of nutrients that are generated through microbial and photochemical activities. In this work, the chemical characteristics of hydrologically connected and isolated cryoconite holes from three geographically distinct regions of coastal Antarctica, namely Larsemann Hills, Amery Ice Shelf and central Dronning Maud Land were studied. Major ions (Na+, K+, Mg2+, Ca2+, Cl−, SO42−and NO3−) and total organic carbon in the hydrologically isolated, closed cryoconite holes showed significantly higher enrichment (6–26 times and 9 times, respectively) over the conservative tracer ion Cl−possibly due to sediment dissolution and microbial synthesis during isolation period. In contrast, depletion of major ions and organic carbon were observed in the open, hydrologically connected holes due to their discharge from the cryoconite holes through interconnected streams. This study suggests that the contribution of cryoconite holes to the nutrient and microbial transport to downstream environments may vary with the extent of hydrological connectivity by virtue of the fact that nutrients and organic carbon which accumulate in the isolated cryoconite holes during isolation could get washed to downstream environments in the event that they get connected through surface or subsurface melt channels.

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St-Laurent, Pierre, Marjorie A. M. Friedrichs, Raymond G. Najjar, Elizabeth H. Shadwick, Hanqin Tian, and Yuanzhi Yao. "Relative impacts of global changes and regional watershed changes on the inorganic carbon balance of the Chesapeake Bay." Biogeosciences 17, no. 14 (July 22, 2020): 3779–96. http://dx.doi.org/10.5194/bg-17-3779-2020.

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Abstract. The Chesapeake Bay is a large coastal-plain estuary that has experienced considerable anthropogenic change over the past century. At the regional scale, land-use change has doubled the nutrient input from rivers and led to an increase in riverine carbon and alkalinity. The bay has also experienced global changes, including the rise of atmospheric temperature and CO2. Here we seek to understand the relative impact of these changes on the inorganic carbon balance of the bay between the early 1900s and the early 2000s. We use a linked land–estuarine–ocean modeling system that includes both inorganic and organic carbon and nitrogen cycling. Sensitivity experiments are performed to isolate the effect of changes in (1) atmospheric CO2, (2) temperature, (3) riverine nitrogen loading and (4) riverine carbon and alkalinity loading. Specifically, we find that over the past century global changes have increased ingassing by roughly the same amount (∼30 Gg-C yr−1) as has the increased riverine loadings. While the former is due primarily to increases in atmospheric CO2, the latter results from increased net ecosystem production that enhances ingassing. Interestingly, these increases in ingassing are partially mitigated by increased temperatures and increased riverine carbon and alkalinity inputs, both of which enhance outgassing. Overall, the bay has evolved over the century to take up more atmospheric CO2 and produce more organic carbon. These results suggest that over the past century, changes in riverine nutrient loads have played an important role in altering coastal carbon budgets, but that ongoing global changes have also substantially affected coastal carbonate chemistry.

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DelDuco, Emily M., and Y. Jun Xu. "Dissolved Carbon Transport and Processing in North America’s Largest Swamp River Entering the Northern Gulf of Mexico." Water 11, no. 7 (July 7, 2019): 1395. http://dx.doi.org/10.3390/w11071395.

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Transport and transformation of riverine dissolved carbon is an important component of global carbon cycling. The Atchafalaya River (AR) flows 189 kilometers through the largest bottomland swamp in North America and discharges ~25% of the flow of the Mississippi River into the Gulf of Mexico annually, providing a unique opportunity to study the floodplain/wetland impacts on dissolved carbon. The aim of this study is to determine how dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the AR change spatially and seasonally, and to elucidate which processes control the carbon cycling in this intricate swamp-river system. From May 2015 to May 2016, we conducted monthly river sampling from the river’s inflow to its outflow, analyzing samples for concentrations and δ13C stable isotope composition of DOC and DIC. We found that DIC concentrations in the AR were three times higher than the DOC concentrations on average, and showed more pronounced downstream changes than the DOC. During the study period, the river discharged a total of 5.35 Tg DIC and a total of 2.34 Tg DOC into the Gulf of Mexico. Based on the mass inflow–outflow balance, approximately 0.53 Tg (~10%) of the total DIC exported was produced within the floodplain/wetland system, while 0.24 Tg (~10%) of the DOC entering the basin was removed. The AR’s water was consistently oversaturated with CO2 partial pressure (pCO2) above the atmospheric pCO2 (with pCO2 varying from 551 µatm to 6922 µatm), indicating a large source of DIC from river waters to the atmosphere as well as to the coastal margins. Largest changes in carbon constituents occurred during periods of greatest inundation of the swamp-river basin and corresponded with shifts in isotopic composition. This effect was particularly pronounced during the initial flood stages, supporting the hypothesis that subtropical floodplains can act as effective enhancers of the biogeochemical cycling of dissolved carbon.

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Lipson, D. A., D. Zona, T. K. Raab, F. Bozzolo, M. Mauritz, and W. C. Oechel. "Water-table height and microtopography control biogeochemical cycling in an Arctic coastal tundra ecosystem." Biogeosciences 9, no. 1 (January 31, 2012): 577–91. http://dx.doi.org/10.5194/bg-9-577-2012.

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Abstract. Drained thaw lake basins (DTLB's) are the dominant land form of the Arctic Coastal Plain in northern Alaska. The presence of continuous permafrost prevents drainage and so water tables generally remain close to the soil surface, creating saturated, suboxic soil conditions. However, ice wedge polygons produce microtopographic variation in these landscapes, with raised areas such as polygon rims creating more oxic microenvironments. The peat soils in this ecosystem store large amounts of organic carbon which is vulnerable to loss as arctic regions continue to rapidly warm, and so there is great motivation to understand the controls over microbial activity in these complex landscapes. Here we report the effects of experimental flooding, along with seasonal and spatial variation in soil chemistry and microbial activity in a DTLB. The flooding treatment generally mirrored the effects of natural landscape variation in water-table height due to microtopography. The flooded portion of the basin had lower dissolved oxygen, lower oxidation-reduction potential (ORP) and higher pH, as did lower elevation areas throughout the entire basin. Similarly, soil pore water concentrations of organic carbon and aromatic compounds were higher in flooded and low elevation areas. Dissolved ferric iron (Fe(III)) concentrations were higher in low elevation areas and responded to the flooding treatment in low areas, only. The high concentrations of soluble Fe(III) in soil pore water were explained by the presence of siderophores, which were much more concentrated in low elevation areas. All the aforementioned variables were correlated, showing that Fe(III) is solubilized in response to anoxic conditions. Dissolved carbon dioxide (CO2) and methane (CH4) concentrations were higher in low elevation areas, but showed only subtle and/or seasonally dependent effects of flooding. In anaerobic laboratory incubations, more CH4 was produced by soils from low and flooded areas, whereas anaerobic CO2 production only responded to flooding in high elevation areas. Seasonal changes in the oxidation state of solid phase Fe minerals showed that net Fe reduction occurred, especially in topographically low areas. The effects of Fe reduction were also seen in the topographic patterns of pH, as protons were consumed where this process was prevalent. This suite of results can all be attributed to the effect of water table on oxygen availability: flooded conditions promote anoxia, stimulating dissolution and reduction of Fe(III), and to some extent, methanogenesis. However, two lines of evidence indicated the inhibition of methanogenesis by alternative e- acceptors such as Fe(III) and humic substances: (1) ratios of CO2:CH4 evolved from anaerobic soil incubations and dissolved in soil pore water were high; (2) CH4 concentrations were negatively correlated with the oxidation state of the soluble Fe pool in both topographically high and low areas. A second set of results could be explained by increased soil temperature in the flooding treatment, which presumably arose from the increased thermal conductivity of the soil surface: higher N mineralization rates and dissolved P concentrations were observed in flooded areas. Overall, these results could have implications for C and nutrient cycling in high Arctic areas where warming and flooding are likely consequences of climate change.

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Pedrazas, Micaela N., M. Bayani Cardenas, Cansu Demir, Jeffery A. Watson, Craig T. Connolly, and James W. McClelland. "Absence of ice-bonded permafrost beneath an Arctic lagoon revealed by electrical geophysics." Science Advances 6, no. 43 (October 2020): eabb5083. http://dx.doi.org/10.1126/sciadv.abb5083.

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Relict permafrost is ubiquitous throughout the Arctic coastal shelf, but little is known about it near shore. The presence and thawing of subsea permafrost are vital information because permafrost stores an atmosphere’s worth of carbon and protects against coastal erosion. Through electrical resistivity imaging across a lagoon on the Alaska Beaufort Sea coast in summer, we found that the subsurface is not ice-bonded down to ~20 m continually from within the lagoon, across the beach, and underneath an ice-wedge polygon on the tundra. This contrasts with the broadly held idea of a gently sloping ice-bonded permafrost table extending from land to offshore. The extensive unfrozen zone is a marine talik connected to on-land cryopeg. This zone is a potential source and conduit for water and dissolved organic matter, is vulnerable to physical degradation, and is liable to changes in biogeochemical processes that affect carbon cycling and climate feedbacks.

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Soulet, Guillaume, Liviu Giosan, Clément Flaux, and Valier Galy. "Using Stable Carbon Isotopes to Quantify Radiocarbon Reservoir Age Offsets in the Coastal Black Sea." Radiocarbon 61, no. 1 (July 18, 2018): 309–18. http://dx.doi.org/10.1017/rdc.2018.61.

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AbstractConstraining radiocarbon (14C) reservoir age offsets is critical to deriving accurate calendar-age chronologies from 14C dating of materials which did not draw carbon directly from the atmosphere. The application of 14C dating to such materials is severely limited in hydrologically sensitive environments like the Black Sea because of the difficulty to quantify reservoir age offsets, which can vary quickly and significantly through time, due to the dynamics of the biogeochemical cycling of carbon. Here we reconstruct 14C reservoir age offsets (Rshell-atm) of Holocene bivalve shells from the coastal Black Sea relatively to their contemporaneous atmosphere. We show that the 14C reservoir age offset and the stable carbon isotope composition of bivalve shells are linearly correlated in this region. From a biogeochemical standpoint, this suggests that inorganic stable carbon isotope and 14C compositions of Black Sea coastal waters are controlled by the balance between autochthonous primary productivity and heterotrophic respiration of allochthonous pre-aged terrestrial organic matter supplied by rivers. This provided an important implication for Black Sea geochronology as the reservoir age offset of 14C-dated bivalve shell can be inferred from its stable carbon isotope composition. Our results provide a fundamental and inexpensive geochemical tool which will considerably improve the accuracy of Holocene calendar age chronologies in the Black Sea.

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Wang, Huaibin, Xiao Xu, Zhihui Wang, Rui Cao, Bingqian Zheng, Siyu Song, Yurui Jiang, Qianyu Zhu, and Wanqin Yang. "Abnormal Litter Induced by Typhoon Disturbances Had Higher Rates of Mass Loss and Carbon Release than Physiological Litter in Coastal Subtropical Urban Forest Ecosystems." Forests 13, no. 11 (November 1, 2022): 1819. http://dx.doi.org/10.3390/f13111819.

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The decomposition of abnormal litter caused by extreme weather events might play an increasingly important role in carbon and nutrient cycling in forest ecosystems under climate change scenarios, which needs to be fully investigated. In August 2020, the abnormal foliar litter of the goldenrain tree (Koelreuteria bipinnata var. Integrifoliola), the camphor tree (Cinnamomum camphora), and the weeping willow (Salix babylonica) after Typhoon Hagupit disturbance were collected and incubated on the soil surface at the Plant Ecology Research Base at Taizhou University, which is located on the eastern coast of China. Simultaneously, the physiological foliar litter of these three trees collected in the spring litter peak was incubated at the same site. The abnormal litter had higher concentrations of carbon (C), nitrogen (N), and phosphorus (P) and lower concentrations of lignin and cellulose than the physiological litter. The accumulative mass loss rates of abnormal litter in the goldenrain tree, the camphor tree, and the weeping willow during the incubation period increased by 7.72%, 29.78%, and 21.76% in comparison with physiological litter, and the corresponding carbon release increased by 9.10%, 24.15% and 19.55%, respectively. The autumn litter peak period and plum-rain season had higher rates of litter mass loss and carbon release, while the winter nongrowing season had lower rates. Accumulative mass loss, accumulative carbon release, daily mass loss and the daily carbon release of foliar litter were significantly and positively correlated with temperature and initial P concentrations, and significantly and negatively correlated with the initial C/P ratio, lignin/N ratio, and lignin/P ratio (p < 0.05). Compared with the physiological litter, abnormal litter had higher initial substrate quality, which may be the most important factor contributing to their high rates of mass loss and carbon release. The results imply that increasing tropical cyclones under climate change scenarios will facilitate carbon cycling in coastal urban forest ecosystems.

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Martin, Patrick, Nagur Cherukuru, Ashleen S. Y. Tan, Nivedita Sanwlani, Aazani Mujahid, and Moritz Müller. "Distribution and cycling of terrigenous dissolved organic carbon in peatland-draining rivers and coastal waters of Sarawak, Borneo." Biogeosciences 15, no. 22 (November 16, 2018): 6847–65. http://dx.doi.org/10.5194/bg-15-6847-2018.

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Abstract. South-East Asia is home to one of the world's largest stores of tropical peatland and accounts for roughly 10 % of the global land-to-sea dissolved organic carbon (DOC) flux. We present the first ever seasonally resolved measurements of DOC concentration and chromophoric dissolved organic matter (CDOM) spectra for six peatland-draining rivers and coastal waters in Sarawak, north-western Borneo. The rivers differed substantially in DOC concentration, ranging from 120–250 µmol L−1 (Rajang River) to 3100–4400 µmol L−1 (Maludam River). All rivers carried high CDOM concentrations, with a350 in the four blackwater rivers between 70 and 210 m−1 and 4 and 12 m−1 in the other two rivers. DOC and CDOM showed conservative mixing with seawater except in the largest river (the Rajang), where DOC concentrations in the estuary were elevated, most likely due to inputs from the extensive peatlands within the Rajang Delta. Seasonal variation was moderate and inconsistent between rivers. However, during the rainier north-east monsoon, all marine stations in the western part of our study area had higher DOC concentrations and lower CDOM spectral slopes, indicating a greater proportion of terrigenous DOM in coastal waters. Photodegradation experiments revealed that riverine DOC and CDOM in Sarawak are photolabile: up to 25 % of riverine DOC was lost within 5 days of exposure to natural sunlight, and the spectral slopes of photo-bleached CDOM resembled those of our marine samples. We conclude that coastal waters of Sarawak receive large inputs of terrigenous DOC that is only minimally altered during estuarine transport and that any biogeochemical processing must therefore occur mostly at sea. It is likely that photodegradation plays an important role in the degradation of terrigenous DOC in these waters.

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Leng, Melanie J., Bernd Wagner, N. John Anderson, Ole Bennike, Ewan Woodley, and Simon J. Kemp. "Deglaciation and catchment ontogeny in coastal south-west Greenland: implications for terrestrial and aquatic carbon cycling." Journal of Quaternary Science 27, no. 6 (May 10, 2012): 575–84. http://dx.doi.org/10.1002/jqs.2544.

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Wang, Shuai, Mingyi Zhou, Qianlai Zhuang, and Liping Guo. "Prediction Potential of Remote Sensing-Related Variables in the Topsoil Organic Carbon Density of Liaohekou Coastal Wetlands, Northeast China." Remote Sensing 13, no. 20 (October 14, 2021): 4106. http://dx.doi.org/10.3390/rs13204106.

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Wetland ecosystems contain large amounts of soil organic carbon. Their natural environment is often both at the junction of land and water with good conditions for carbon sequestration. Therefore, the study of accurate prediction of soil organic carbon (SOC) density in coastal wetland ecosystems of flat terrain areas is the key to understanding their carbon cycling. This study used remote sensing data to study SOC density potentials of coastal wetland ecosystems in Northeast China. Eleven environmental variables including normalized difference vegetation index (NDVI), difference vegetation index (DVI), soil adjusted vegetation index (SAVI), renormalization difference vegetation index (RDVI), ratio vegetation index (RVI), topographic wetness index (TWI), elevation, slope aspect (SA), slope gradient (SG), mean annual temperature (MAT), and mean annual precipitation (MAP) were selected to predict SOC density. A total of 193 soil samples (0–30 cm) were divided into two parts, 70% of the sampling sites data were used to construct the boosted regression tree (BRT) model containing three different combinations of environmental variables, and the remaining 30% were used to test the predictive performance of the model. The results show that the full variable model is better than the other two models. Adding remote sensing-related variables significantly improved the model prediction. This study revealed that SAVI, NDVI and DVI were the main environmental factors affecting the spatial variation of topsoil SOC density of coastal wetlands in flat terrain areas. The mean (±SD) SOC density of full variable models was 18.78 (±1.95) kg m−2, which gradually decreased from northeast to southwest. We suggest that remote sensing-related environmental variables should be selected as the main environmental variables when predicting topsoil SOC density of coastal wetland ecosystems in flat terrain areas. Accurate prediction of topsoil SOC density distribution will help to formulate soil management policies and enhance soil carbon sequestration.

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Stuart, Rhona K., Chris L. Dupont, D. Aaron Johnson, Ian T. Paulsen, and Brian Palenik. "Coastal Strains of Marine Synechococcus Species Exhibit Increased Tolerance to Copper Shock and a Distinctive Transcriptional Response Relative to Those of Open-Ocean Strains." Applied and Environmental Microbiology 75, no. 15 (June 5, 2009): 5047–57. http://dx.doi.org/10.1128/aem.00271-09.

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ABSTRACT Copper appears to be influencing the distribution and abundance of phytoplankton in marine environments, and cyanobacteria are thought to be the most sensitive of the phytoplankton groups to copper toxicity. By using growth assays of phylogenetically divergent clades, we found that coastal strains of marine Synechococcus species were more tolerant to copper shock than open-ocean strains. The global transcriptional response to two levels of copper shock were determined for both a coastal strain and an open-ocean strain of marine Synechococcus species using whole-genome expression microarrays. Both strains showed an osmoregulatory-like response, perhaps as a result of increasing membrane permeability. This could have implications for marine carbon cycling if copper shock leads to dissolved organic carbon leakage in Synechococcus species. The two strains additionally showed a common reduction in levels of photosynthesis-related gene transcripts. Contrastingly, the open-ocean strain showed a general stress response, whereas the coastal strain exhibited a more specifically oxidative or heavy-metal acclimation response that may be conferring tolerance. In addition, the coastal strain activated more regulatory elements and transporters, many of which are not conserved in other marine Synechococcus strains and may have been acquired by horizontal gene transfer. Thus, tolerance to copper shock in some marine Synechococcus strains may in part be a result of a generally increased ability to sense and respond in a more stress-specific manner.

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Sun, Feifei, Xiaoli Zhang, Qianqian Zhang, Fanghua Liu, Jianping Zhang, and Jun Gong. "Seagrass (Zostera marina) Colonization Promotes the Accumulation of Diazotrophic Bacteria and Alters the Relative Abundances of Specific Bacterial Lineages Involved in Benthic Carbon and Sulfur Cycling." Applied and Environmental Microbiology 81, no. 19 (July 24, 2015): 6901–14. http://dx.doi.org/10.1128/aem.01382-15.

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ABSTRACTSeagrass colonization changes the chemistry and biogeochemical cycles mediated by microbes in coastal sediments. In this study, we molecularly characterized the diazotrophic assemblages and entire bacterial community in surface sediments of aZostera marina-colonized coastal lagoon in northern China. Higher nitrogenase gene (nifH) copy numbers were detected in the sediments from the vegetated region than in the sediments from the unvegetated region nearby. ThenifHphylotypes detected were mostly affiliated with theGeobacteraceae,Desulfobulbus,Desulfocapsa, andPseudomonas. Redundancy analysis based on terminal restriction fragment length polymorphism analysis showed that the distribution ofnifHgenotypes was mostly shaped by the ratio of total organic carbon to total organic nitrogen, the concentration of cadmium in the sediments, and the pH of the overlying water. High-throughput sequencing and phylogenetic analyses of bacterial 16S rRNA genes also indicated the presence ofGeobacteraceaeandDesulfobulbaceaephylotypes in these samples. A comparison of these results with those of previous studies suggests the prevalence and predominance of iron(III)-reducingGeobacteraceaeand sulfate-reducingDesulfobulbaceaediazotrophs in coastal sedimentary environments. Although the entire bacterial community structure was not significantly different between these two niches,Desulfococcus(Deltaproteobacteria) andAnaerolineae(Chloroflexi) presented with much higher proportions in the vegetated sediments, andFlavobacteriaceae(Bacteroidetes) occurred more frequently in the bare sediments. These data suggest that the high bioavailability of organic matter (indicated by relatively lower carbon-to-nitrogen ratios) and the less-reducing anaerobic condition in vegetated sediments may favorDesulfococcusandAnaerolineaelineages, which are potentially important populations in benthic carbon and sulfur cycling in the highly productive seagrass ecosystem.

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Zhou, Yongli, Patrick Martin, and Moritz Müller. "Composition and cycling of dissolved organic matter from tropical peatlands of coastal Sarawak, Borneo, revealed by fluorescence spectroscopy and parallel factor analysis." Biogeosciences 16, no. 13 (July 12, 2019): 2733–49. http://dx.doi.org/10.5194/bg-16-2733-2019.

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Abstract. Southeast Asian peatlands supply ∼10 % of the global flux of dissolved organic carbon (DOC) from land to the ocean, but the biogeochemical cycling of this peat-derived DOC in coastal environments is still poorly understood. Here, we use fluorescence spectroscopy and parallel factor (PARAFAC) analysis to distinguish different fractions of dissolved organic matter (DOM) in peat-draining rivers, estuaries and coastal waters of Sarawak, Borneo. The terrigenous fractions showed high concentrations at freshwater stations within the rivers, and conservative mixing with seawater across the estuaries. The autochthonous DOM fraction, in contrast, showed low concentrations throughout our study area at all salinities. The DOM pool was also characterized by a high degree of humification in all rivers and estuaries up to salinities of 25. These results indicate a predominantly terrestrial origin of the riverine DOM pool. Only at salinities > 25 did we observe an increase in the proportion of autochthonous relative to terrestrial DOM. Natural sunlight exposure experiments with river water and seawater showed high photolability of the terrigenous DOM fractions, suggesting that photodegradation may account for the observed changes in the DOM composition in coastal waters. Nevertheless, based on our fluorescence data, we estimate that at least 20 %–25 % of the DOC at even our most marine stations (salinity > 31) was terrestrial in origin, indicating that peatlands likely play an important role in the carbon biogeochemistry of Southeast Asian shelf seas.

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Wu, Liyou, Laurie Kellogg, Allan H. Devol, James M. Tiedje, and Jizhong Zhou. "Microarray-Based Characterization of Microbial Community Functional Structure and Heterogeneity in Marine Sediments from the Gulf of Mexico." Applied and Environmental Microbiology 74, no. 14 (May 30, 2008): 4516–29. http://dx.doi.org/10.1128/aem.02751-07.

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ABSTRACT Marine sediments of coastal margins are important sites of carbon sequestration and nitrogen cycling. To determine the metabolic potential and structure of marine sediment microbial communities, two cores were collected each from the two stations (GMT at a depth of 200 m and GMS at 800 m) in the Gulf of Mexico, and six subsamples representing different depths were analyzed from each of these two cores using functional gene arrays containing ∼2,000 probes targeting genes involved in carbon fixation; organic carbon degradation; contaminant degradation; metal resistance; and nitrogen, sulfur, and phosphorous cycling. The geochemistry was highly variable for the sediments based on both site and depth. A total of 930 (47.1%) probes belonging to various functional gene categories showed significant hybridization with at least 1 of the 12 samples. The overall functional gene diversity of the samples from shallow depths was in general lower than those from deep depths at both stations. Also high microbial heterogeneity existed in these marine sediments. In general, the microbial community structure was more similar when the samples were spatially closer. The number of unique genes at GMT increased with depth, from 1.7% at 0.75 cm to 18.9% at 25 cm. The same trend occurred at GMS, from 1.2% at 0.25 cm to 15.2% at 16 cm. In addition, a broad diversity of geochemically important metabolic functional genes related to carbon degradation, nitrification, denitrification, nitrogen fixation, sulfur reduction, phosphorus utilization, contaminant degradation, and metal resistance were observed, implying that marine sediments could play important roles in biogeochemical cycling of carbon, nitrogen, phosphorus, sulfate, and various metals. Finally, the Mantel test revealed significant positive correlations between various specific functional genes and functional processes, and canonical correspondence analysis suggested that sediment depth, PO4 3−, NH4 +, Mn(II), porosity, and Si(OH)4 might play major roles in shaping the microbial community structure in the marine sediments.

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Klootwijk, Anouk T., Andrew K. Sweetman, Silvia Hess, Elisabeth Alve, Kathrine M. Dunlop, and Paul E. Renaud. "Benthic foraminiferal carbon cycling in coastal zone sediments: The influence of the assemblage structure and jellyfish detritus." Estuarine, Coastal and Shelf Science 261 (October 2021): 107535. http://dx.doi.org/10.1016/j.ecss.2021.107535.

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Lugomela, C. "Plankton composition and cycling of carbon during the rainy season in a tropical coastal ecosystem, Zanzibar, Tanzania." Journal of Plankton Research 23, no. 10 (October 1, 2001): 1121–36. http://dx.doi.org/10.1093/plankt/23.10.1121.

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Journal articles on the topic 'Coastal carbon cycling'

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