Geochemical conditions for the preservation of recent aragonite-rich sediments in Mediterranean karstic marine lakes (Mljet Island, Adriatic Sea, Croatia)

2010 ◽  
Vol 61 (1) ◽  
pp. 119 ◽  
Author(s):  
Sonja Lojen ◽  
Ivan Sondi ◽  
Mladen Juracic
Keyword(s):  
Pore Water ◽  
Inorganic Carbon ◽  
Adriatic Sea ◽  
Dissolved Inorganic Carbon ◽  
Carbonate Content ◽  
Carbonate Dissolution ◽  
Saturation State ◽  
Organic Debris ◽  
Geochemical Parameters ◽  
Marine Lakes

Conditions for the preservation of recent aragonite-rich sediments during early diagenesis in two semi-enclosed Mediterranean karstic seawater lakes on the island of Mljet (Adriatic Sea) were examined. The concentrations and stable isotope compositions of carbonate and sedimentary organic matter, as well as the geochemical parameters in pore water were measured. It was found that the smaller lake (Malo Jezero) receives considerably more terrestrial detritus than the larger lake (Veliko Jezero). A decrease in carbonate δ13C values with depth indicated a rather intensive transfer of organically derived C into the carbonate pool by diagenetic recrystallisation, masking the changes in carbonate δ13C caused by increasing amounts of aragonite. Dissolution of calcite as a result of CO2 released from the decomposition of organic debris and the upward diffusive flux of dissolved inorganic carbon were together responsible for up to 24% of the dissolved inorganic carbon added to the pore water. This indicated locally occurring carbonate dissolution, irrespective of its saturation state in the bulk sediment. Despite the larger input of terrigenous material into Malo Jezero, the carbonate content in the sediment was much higher than in Veliko Jezero, indicating greater authigenic aragonite production. As magnesium calcite accounted for most of the carbonate dissolution, aragonite preservation in the sediment is favoured.

scholarly journals Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany

2008 ◽  
Vol 5 (6) ◽  
pp. 1615-1623 ◽  
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Calcareous Fens ◽  
Essential Components ◽  
The Individual

Abstract. Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of calcareous fens under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO2 in all forms of DIC appears to be an important part of peatland C-balance.

scholarly journals Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

2017 ◽  
Author(s):  
Jacoba Mol ◽  
Helmuth Thomas ◽  
Paul G. Myers ◽  
Xianmin Hu ◽  
Alfonso Mucci
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Beaufort Sea ◽  
Total Alkalinity ◽  
The Arctic ◽  
Surface Mixed Layer ◽  
Saturation State ◽  
Carbon Transfer ◽  
Mackenzie Shelf

Abstract. The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries inorganic carbon and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world oceans. Upwelling carries dissolved inorganic carbon (DIC) and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of inorganic carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of inorganic carbon are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf is analyzed and the resulting influence on the carbonate system, including the saturation state of waters with respect to aragonite and pH, is investigated. TA and the oxygen isotope ratio of water (δ18O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

Ocean acidification as a multiple driver: how interactions between changing seawater carbonate parameters affect marine life

2020 ◽  
Vol 71 (3) ◽  
pp. 263 ◽  
Author(s):  
Catriona L. Hurd ◽  
John Beardall ◽  
Steeve Comeau ◽  
Christopher E. Cornwall ◽  
Jonathan N Havenhand ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Multiple Stressors ◽  
Rapid Expansion ◽  
Coralline Algae ◽  
Carbonate System ◽  
Saturation State ◽  
Marine Life ◽  
Key Terms

‘Multiple drivers’ (also termed ‘multiple stressors’) is the term used to describe the cumulative effects of multiple environmental factors on organisms or ecosystems. Here, we consider ocean acidification as a multiple driver because many inorganic carbon parameters are changing simultaneously, including total dissolved inorganic carbon, CO2, HCO3–, CO32–, H+ and CaCO3 saturation state. With the rapid expansion of ocean acidification research has come a greater understanding of the complexity and intricacies of how these simultaneous changes to the seawater carbonate system are affecting marine life. We start by clarifying key terms used by chemists and biologists to describe the changing seawater inorganic carbon system. Then, using key groups of non-calcifying (fish, seaweeds, diatoms) and calcifying (coralline algae, coccolithophores, corals, molluscs) organisms, we consider how various physiological processes are affected by different components of the carbonate system.

Isotopic and geochemical composition of marl lake waters and implications for radiocarbon dating of marl lake sediments

1983 ◽  
Vol 20 (4) ◽  
pp. 599-615 ◽  
Author(s):  
J. V. Turner ◽  
P. Fritz ◽  
P. F. Karrow ◽  
B. G. Warner
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Sediment Cores ◽  
Geochemical Composition ◽  
Radiocarbon Dates ◽  
Southern Ontario ◽  
Suitable Material ◽  
Geochemical Parameters ◽  
Marl Lake ◽  
Lake Waters

Radiocarbon dates on organic and calcareous fractions of sediment cores from marl lakes may yield anomalous ages due to the assumption of a constant hardwater correction factor along the sediment sequence. A study of eight marl lakes in southern Ontario that are actively precipitating calcium carbonate was conducted in order to assess those isotopic and aqueous geochemical parameters in modern lakes that may be utilized to estimate the history and extent of variations in the hardwater effect along such sediment sequences. Results show an increase in the δ13C composition of lake DIC (dissolved inorganic carbon) as approach to isotopic equilibrium with atmospheric CO2 occurs. Differences in the extent to which this equilibrium is established also appear responsible for observed differences in the 14C activity of DIC between lakes of as much as 20 pmc (percent modern carbon). These variations have been related to the relative residence times of water in each lake by examination of their corresponding seasonal variations in 18O and 2H content. Consequently δ13C and δ18O of marl and molluscs have been used to identify variations in the hardwater effect along the sediment profile. A profile of radiocarbon dates on marl from Little Lake in southern Ontario shows satisfactory agreement with an independently determined pollen chronology. Where certain criteria are met, marl deposits appear to be suitable material for establishing Quaternary chronology.

Variations in the Isotopic Composition of Dissolved Inorganic Carbon in the Unsaturated Zone of a Semi-Arid Region

Radiocarbon ◽  
2015 ◽  
Vol 57 (3) ◽  
pp. 397-406 ◽  
Author(s):  
I Carmi ◽  
D Yakir ◽  
Y Yechieli ◽  
J Kronfield ◽  
M Stiller
Keyword(s):  
Unsaturated Zone ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Sediment Cores ◽  
Tritium Content ◽  
Organic Debris ◽  
Different Seasons ◽  
Semi Arid Region ◽  
Semi Arid

A study of water and carbon isotopes was conducted in a bare plot in the unsaturated zone of the Yatir Forest in the northern Negev of Israel. Sediment cores were collected in three different seasons. Measurements include profiles of mineralogy, moisture and its δ18O and tritium content, dissolved inorganic carbon (DIC) and its δ13C (‰) and Δ14C (‰) content, and δ13C (‰) and Δ14C (‰) in the solid sediment. The profiles of moisture and δ18O in the cores show clearly the effect of evaporation. The tritium profile indicates infiltration of water (0.11 m yr−1). The source of carbon in the DIC is CO2 released by biotic activity through roots of trees and of seasonal plants, which show seasonal variations, and by decay of organic debris. The δ13C (‰) profiles show clearly the chemical transition from dissolved CO2 (δ13C = −22‰) to bicarbonate (δ13C = −14‰). At greater depth (–11.3‰), the δ13C becomes similar to the δ13C in the aquifer below (–12.5‰). The effect of secondary processes is evident in the profile of Δ14C in the DIC. It shows a clear decrease with depth due to exchange with the sediment at a rate of 10‰ yr−1. Precipitation of carbon from the DIC on the sediment is 1.1 mg C Lsed−1 yr−1, negligible compared to the 28 g C in 1 Lsed. In the solid sediment, there is a gradient in Δ14Ccarb at the top meter. The net precipitation of 14C from the DIC on the sediment (0.25 to 1.1‰ yr−1), corrected for decay, cannot be observed in the deeper sediment. The presence of 14C in the top 1 m of the sediment is explained by two possible processes: accumulation of 14C-tagged dust (∼0.05 mm yr−1) and/or long-term cumulative precipitation from the DIC.

scholarly journals The relevance of particulate organic carbon (POC) for carbon composition in the pore water of drained and rewetted fens of the "Donauried" (South-Germany)

2008 ◽  
Vol 5 (3) ◽  
pp. 2049-2073
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Soil C ◽  
Calcareous Fen ◽  
Essential Components

Abstract. Numerous studies have dealt with carbon (C) concentrations in Histosols, but there are no studies quantifying the relative importance of all individual C components in pore waters. For this study, measurements were made of all the carbon components (i.e., particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of a calcareous fen under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C transfer in the soil profile ("C-Shuttles"). Consequently, it was concluded that POC is at least as important as DOC for internal soil C turnover. There is no reason to assume significant biochemical differences between POC and DOC as they only differ in size. Therefore, both POC and DOC fractions are essential components of C budgets of peatlands. Furthermore dissolved CO2 in all forms of DIC apparently is an important part of peatland C-balances.

scholarly journals A regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of Alaska

2020 ◽  
Vol 17 (14) ◽  
pp. 3837-3857
Author(s):  
Claudine Hauri ◽  
Cristina Schultz ◽  
Katherine Hedstrom ◽  
Seth Danielson ◽  
Brita Irving ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Seasonal Cycle ◽  
Bottom Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Gulf Of Alaska ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Carbon Chemistry ◽  
Seward Line

Abstract. The coastal ecosystem of the Gulf of Alaska (GOA) is especially vulnerable to the effects of ocean acidification and climate change. Detection of these long-term trends requires a good understanding of the system’s natural state. The GOA is a highly dynamic system that exhibits large inorganic carbon variability on subseasonal to interannual timescales. This variability is poorly understood due to the lack of observations in this expansive and remote region. We developed a new model setup for the GOA that couples the three-dimensional Regional Oceanic Model System (ROMS) and the Carbon, Ocean Biogeochemistry and Lower Trophic (COBALT) ecosystem model. To improve our conceptual understanding of the system, we conducted a hindcast simulation from 1980 to 2013. The model was explicitly forced with temporally and spatially varying coastal freshwater discharges from a high-resolution terrestrial hydrological model, thereby affecting salinity, alkalinity, dissolved inorganic carbon, and nutrient concentrations. This represents a substantial improvement over previous GOA modeling attempts. Here, we evaluate the model on seasonal to interannual timescales using the best available inorganic carbon observations. The model was particularly successful in reproducing observed aragonite oversaturation and undersaturation of near-bottom water in May and September, respectively. The largest deficiency in the model is its inability to adequately simulate springtime surface inorganic carbon chemistry, as it overestimates surface dissolved inorganic carbon, which translates into an underestimation of the surface aragonite saturation state at this time. We also use the model to describe the seasonal cycle and drivers of inorganic carbon parameters along the Seward Line transect in under-sampled months. Model output suggests that the majority of the near-bottom water along the Seward Line is seasonally undersaturated with respect to aragonite between June and January, as a result of upwelling and remineralization. Such an extensive period of reoccurring aragonite undersaturation may be harmful to ocean acidification-sensitive organisms. Furthermore, the influence of freshwater not only decreases the aragonite saturation state in coastal surface waters in summer and fall, but it simultaneously decreases the surface partial pressure of carbon dioxide (pCO2), thereby decoupling the aragonite saturation state from pCO2. The full seasonal cycle and geographic extent of the GOA region is under-sampled, and our model results give new and important insights for months of the year and areas that lack in situ inorganic carbon observations.

scholarly journals CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

2009 ◽  
Vol 6 (10) ◽  
pp. 2145-2153 ◽  
Author(s):  
K. G. Schulz ◽  
J. Barcelos e Ramos ◽  
R. E. Zeebe ◽  
U. Riebesell
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Calcium Carbonate Precipitation ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
Experimental Conditions ◽  
Saturation State ◽  
Basic Approaches

Abstract. Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3−) at the expense of carbonate ion (CO32−) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation.

scholarly journals Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

2016 ◽  
Vol 10 (5) ◽  
pp. 2173-2189 ◽  
Author(s):  
Nicolas-Xavier Geilfus ◽  
Ryan J. Galley ◽  
Brent G. T. Else ◽  
Karley Campbell ◽  
Tim Papakyriakou ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dynamics ◽  
Total Alkalinity ◽  
Main Process ◽  
Saturation State ◽  
Ice Growth ◽  
Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

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