Carbonate System

The South Atlantic Ocean is currently undergoing significant alterations due to climate change. This region is important to the global carbon cycle, but marine carbon data are scarce in this basin. Additionally, this region is influenced by Agulhas eddies. However, their effects on ocean biogeochemistry are not yet fully understood. Thus, we aimed to model the carbonate parameters in this region and investigate the anthropogenic carbon (C ant ) content in 13 eddies shed by the Agulhas retroflection. We used in situ data from the CLIVAR/WOCE/A10 section to elaborate total dissolved inorganic carbon (C T ) and total alkalinity (A T ) models and reconstruct those parameters using in situ data from two other Brazilian initiatives. Furthermore, we applied the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) method to calculate the C ant , focusing on the 13 identified Agulhas eddies. The C T and A T models presented root mean square errors less than 1.66 and 2.19 µmol kg -1 , indicating Global Ocean Acidification Observing Network climate precision. The C ant content in the Agulhas eddies was 23% higher than that at the same depths of the surrounding waters. We observed that Agulhas eddies can play a role in the faster acidification of the South Atlantic Central Water.

A three-dimensional coupled physicalbiogeochemical model was used to simulate and examine temporal and spatial variability of sea surface pCO 2 in the Gulf of Mexico (GoM). The model was driven by realistic atmospheric forcing, open boundary conditions from a dataassimilative global ocean circulation model, and observed freshwater and terrestrial nutrient and carbon input from major rivers. A 7-year model hindcast (2004-2010) was performed and validated against ship measurements. Model results revealed clear seasonality in surface pCO 2 and were used to estimate carbon budgets in the Gulf. Based on the average of model simulations, the GoM was a net CO 2 sink with a flux of 1.11 ± 0.84 × 10 12 mol C yr −1 , which, together with the enormous fluvial inorganic carbon input, was comparable to the inorganic carbon export through the Loop Current. Two model sensitivity experiments were performed: one without biological sources and sinks and the other using river input from the 1904-1910 period as simulated by the Dynamic Land Ecosystem Model (DLEM). It was found that biological uptake was the primary driver making GoM an overall CO 2 sink and that the carbon flux in the northern GoM was very susceptible to changes in river forcing. Large uncertainties in model simulations warrant further process-based investigations.

The seasonal variability of the carbonate system in the eastern Mediterranean Sea (EMed) was investigated based on discrete total alkalinity (A T), total dissolved inorganic carbon (C T), and pH measurements collected during three cruises around Crete between June 2018 and March 2019. This study presents a detailed description of this new carbonate chemistry dataset in the eastern Mediterranean Sea. We show that the North Western Levantine Basin (NWLB) is unique in terms of range of A T variation vs. C T variation in the upper water column over an annual cycle. The reasons for this singularity of the NWLB can be explained by the interplay between strong evaporation and the concomitant consumption of C T by autotrophic processes. The high range of A T variations, combined to temperature changes, has a strong impact on the variability of the seawater pCO 2 (pCO 2 SW). Based on Argo float data, an entire annual cycle for pCO 2 SW in the NWLB has been reconstructed in order to estimate the temporal sequence of the potential "source" and "sink" of atmospheric CO 2. By combining this dataset with previous observations in the NWLB, this study shows a significant ocean acidification and a decrease in the oceanic surface pH T 25 of −0.0024 ± 0.0004 pH T 25 units.a −1. The changes in the carbonate system are driven by the increase of atmospheric CO 2 but also by unexplained temporal changes in the surface A T content. If we consider that the EMed will, in the future, encounter longer, more intense and warmer summer seasons, this study proposes some perspectives on the carbonate system functioning of the "future" EMed.

RESUMO-O fluxo de carbono inorgânico dissolvido (CID) no Rio Piracicaba, no distrito de Artemis (Piracicaba, São Paulo) foi determinado a partir dos cálculos de seus principais componentes fluviais, de acordo com as reações de equilíbrio do sistema carbonato, utilizando somente como base os parâmetros pH, temperatura e alcalinidade total, além das respectivas vazões durante o período de amostragem. Os resultados obtidos mostraram que o CID fluvial, com um fluxo de 40.383 tC.a-1 , é principalmente controlado pelos processos biogênicos ligados ao consumo de CO 2 atmosférico/solo, incluindo a alteração de silicatos e dissolução de carbonatos, apresentando como espécies dominantes o HCO 3-, com 32.811 tC.a-1 (81%) e CO 2 dissolvido com 7.557 tC.a-1 (19%), enquanto o CO 3 2representou menos de 0,1%. Do total de carbono transportado fluvialmente na bacia de drenagem do Rio Piracicaba, o CID, representado pelo HCO 3-, foi superior ao carbono orgânico dissolvido, o qual apresentou um fluxo de 22.064 tC.a-1 , fluxo esse principalmente associado aos aportes domésticos. Palavras-chave: Rio Piracicaba, sistema de carbonatos, CID, CO 2 dissolvido.

This study combines measurements of dissolved inorganic carbon (DIC), total alkalinity (TA), pH, earth observation (EO), and ocean model products with deep learning to provide a good step forward in detecting changes in the ocean carbonate system parameters at a high spatial and temporal resolution in the North Atlantic region (Long. −61.00° to −50.04° W; Lat. 24.99° to 34.96° N). The in situ reference dataset that was used for this study provided discrete underway measurements of DIC, TA, and pH collected by M/V Equinox in the North Atlantic Ocean. A unique list of co-temporal and co-located global daily environmental drivers derived from independent sources (using satellite remote sensing, model reanalyses, empirical algorithms, and depth soundings) were collected for this study at the highest possible spatial resolution (0.04° × 0.04°). The resulting ANN-estimated DIC, TA, and pH obtained by deep learning shows a high correspondence when verified against observations. This study ...

Data of A T (total alkalinity) and C T (total inorganic carbon) collected during October 2013, on a N-S transect crossing the North of Lemnos basin allowed to identify the peculiarities of the CO 2 system in the North Aegean Sea and estimate the anthropogenic CO 2 (C ANT) concentrations. Extremely high concentrations of A T and C T were recorded in the upper layer of the North Aegean reflecting the high loads of A T and C T by the brackish BSW (Black Sea Water) outflowing through the Dardanelles strait and by the local rivers runoff. Both A T and C T exhibit strong negative linear correlation with salinity in the upper layer (0-20m). Investigation of the A T-S relationship along with the salinity adjustment of A T revealed excess alkalinity throughout the water column in relation to surface waters implying the possible occurrence of non-carbonate alkalinity inputs and of other processes taking place probably over the extended shelves that contribute to the alkalinity surplus. The intermediate layer occupied by the Modified Levantine Intermediate Water (MLIW) mass exhibits the lowest C T and A T concentrations, while rather elevated A T and C T concentrations characterize the North Aegean Deep Water (NAgDW) mass filling the deep layer of the North of Lemnos basin linked to previous dense water formation episodes. High anthropogenic CO 2 content was detected at intermediate and deep layers of the North Aegean reflecting the effective transportation of the absorbed atmospheric CO 2 at the surface to the deeper waters via the dense water formation episodes. The MLIW layer is more affected by the penetration of C ANT than the NAgDW that fills the deep part of the basin. The observed variability of C ANT distribution reflects the influence of the intensity of dense water formation events, of the different θ/S properties of the newly formed dense waters as well as of the diverse submarine pathways followed by the cascading dense waters. The invasion of C ANT has lead to more acidic conditions and to lower saturation degree of calcium carbonate in relation to the preindustrial era. The findings of this study provide baseline information about the carbonate system properties of the North Aegean and highlight its active role in sequestering and storing anthropogenic CO 2 .

Ocean acidification (OA) is a serious consequence of climate change with complex organism-to-ecosystem effects that have been observed through field observations but are mainly derived from experimental studies. Although OA trends and the resulting biological impacts are likely exacerbated in the semi-enclosed and highly populated Mediterranean Sea, some fundamental knowledge gaps still exist. These gaps are at tributed to both the uneven capacity for OA research that exists between Mediterranean countries, as well as to the subtle and long-term biological, physical and chemical interactions that define OA impacts. In this paper, we systematically analyzed the different aspects of OA research in the Mediterranean region based on two sources: the United Nation’s International Atomic Energy Agency’s (IAEA) Ocean Acidification International Coordination Center (OA-ICC) database, and an extensive survey. Our analysis shows that 1) there is an uneven geographic capacity in OA research, a...

Ocean acidification (OA) is a serious consequence of climate change with complex organism-to-ecosystem effects that have been observed through field observations but are mainly derived from experimental studies. Although OA trends and the resulting biological impacts are likely exacerbated in the semi-enclosed and highly populated Mediterranean Sea, some fundamental knowledge gaps still exist. These gaps are at tributed to both the uneven capacity for OA research that exists between Mediterranean countries, as well as to the subtle and long-term biological, physical and chemical interactions that define OA impacts. In this paper, we systematically analyzed the different aspects of OA research in the Mediterranean region based on two sources: the United Nation’s International Atomic Energy Agency’s (IAEA) Ocean Acidification International Coordination Center (OA-ICC) database, and an extensive survey. Our analysis shows that 1) there is an uneven geographic capacity in OA research, a...

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO 2 (pCO 2) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a fully controlled continuous culture facility. Two levels of phosphorous limitation were consecutively applied by renewal of culture media (N:P = 26) at dilution rates (D) of 0.3 d − 1 and 0.1 d − 1. CO 2 and temperature conditions were 300, 550 and 900 μatm pCO 2 at 14°C and 900 μatm pCO 2 at 18°C. In general, the steady state cell density and particulate organic carbon (POC) production increased with pCO 2 , yielding significantly higher concentrations in cultures grown at 900 μatm pCO 2 compared to 300 and 550 μatm pCO 2. At 900 μatm pCO 2 , elevation of temperature as expected for a greenhouse ocean, further increased cell densities and POC concentrations. In contrast to POC concentration, C-quotas (pmol C cell − 1) were similar at D = 0.3 d − 1 in all cultures. At D = 0.1 d − 1 , a reduction of C-quotas by up to 15% was observed in the 900 μatm pCO 2 at 18°C culture. As a result of growth rate reduction, POC:PON:POP ratios deviated strongly from the Redfield ratio, primarily due to an increase in POC. Ratios of particulate inorganic and organic carbon (PIC:POC) ranged from 0.14 to 0.18 at D = 0.3 d − 1 , and from 0.11 to 0.17 at D =0.1 d − 1 , with variations primarily induced by the changes in POC. At D = 0.1 d − 1 , cell volume was reduced by up to 22% in cultures grown at 900 μatm pCO 2. Our results indicate that changes in pCO 2 , temperature and phosphorus supply affect cell density, POC concentration and size of E. huxleyi (PML B92/11) to varying degrees, and will likely impact bloom development as well as biogeochemical cycling in a greenhouse ocean.

Ocean acidification (OA) is a serious consequence of climate change with complex organism-to-ecosystem effects that have been observed through field observations but are mainly derived from experimental studies. Although OA trends and the resulting biological impacts are likely exacerbated in the semi-enclosed and highly populated Mediterranean Sea, some fundamental knowledge gaps still exist. These gaps are at tributed to both the uneven capacity for OA research that exists between Mediterranean countries, as well as to the subtle and long-term biological, physical and chemical interactions that define OA impacts. In this paper, we systematically analyzed the different aspects of OA research in the Mediterranean region based on two sources: the United Nation’s International Atomic Energy Agency’s (IAEA) Ocean Acidification International Coordination Center (OA-ICC) database, and an extensive survey. Our analysis shows that 1) there is an uneven geographic capacity in OA research, a...

A high-resolution nutrient biochemistry and carbonate system surface synoptic data set from the N-NE Brazilian continental shelf was reanalyzed to fill a gap in the time series of the carbonate system in the region and to allow us to perform a historical analysis of its evolution in recent years. We used data collected from 7 oceanographic cruises (n=852) undertaken between March 1995 and September 2001 during the Brazilian Program "REVIZEE" in the North (N) and Northeast (NE) Economical Exclusive Zones of Brazil. Measured temperature and salinity data, which exhibited strong fluctuations (25.5ºC-29.5ºC and 13.2-37.4 units, respectively), showed significant differences between the N and NE campaigns. The concentrations of dissolved inorganic nitrogen (DIN), PO 4 and SiO 2 were higher in the N region than in the NE region, mainly due to fluvial transport, and nitrogen: phosphorus (N:P) ratios of <16 and oxygen supersaturation were observed within the Amazon plume. The concentrations of riverine nutrients in the N region support primary production occurring in the offshore plume area. The calculated total alkalinity (1,031-2,437 mol kg-1) values showed strong spatial variations that were mainly associated with the Amazon plume. The calculated pCO 2 values reached 423 atm offshore in the NE region during boreal winter. The calculated sea-air CO 2 fluxes (average: +0.31.7 mmoles m-2 d-1 ; range:-1.2 to +2.0 mmoles m-2 d-ACCEPTED MANUSCRIPT 2 1) showed spatial and temporal variations, with negative values (sink) in the region of the Amazon River plume and positive values (source) offshore in the NE region (4ºS to 12ºS). The variability in the sea-air CO 2 fluxes in the N and NE regions was explained by variations in biological activity and the thermodynamic effect of temperature, respectively. The analysis of available data, complemented with those presented here, indicated that the surface water pCO 2 values showed a positive temporal trend (+1.10±0.2 atm yr-1) in the NE region during the period of 1987-2010. This rate of increase is lower than that verified to have occurred in the atmosphere (+1.72±0.01 atm yr-1) during the same period.

Ocean acidification (OA) is a serious consequence of climate change with complex organism-to-ecosystem effects that have been observed through field observations but are mainly derived from experimental studies. Although OA trends and the resulting biological impacts are likely exacerbated in the semi-enclosed and highly populated Mediterranean Sea, some fundamental knowledge gaps still exist. These gaps are at tributed to both the uneven capacity for OA research that exists between Mediterranean countries, as well as to the subtle and long-term biological, physical and chemical interactions that define OA impacts. In this paper, we systematically analyzed the different aspects of OA research in the Mediterranean region based on two sources: the United Nation’s International Atomic Energy Agency’s (IAEA) Ocean Acidification International Coordination Center (OA-ICC) database, and an extensive survey. Our analysis shows that 1) there is an uneven geographic capacity in OA research, a...

The Southern Ocean is a climatically sensitive region that plays an important role in the regional and global modulation of atmospheric CO 2. Based on satellite-derived sea ice data, wind and cloudiness estimates from numerical models (National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis), and in situ measurements of surface (0-20 m depth) chlorophyll a (Chl Surf) and dissolved inorganic carbon (DIC Surf) concentration, we show sea ice concentration from June to November and spring wind patterns between 1979 and 2006 had a significant influence on midsummer (January) primary productivity and carbonate chemistry for the Western Shelf of the Antarctic Peninsula (WAP, 64°-68°S, 63.4°-73.3°W). In general, strong (>3.5 m s −1) and persistent (>2 months) northerly winds during the previous spring were associated with relatively high (monthly mean > 2 mg m −3) Chl Surf and low (monthly mean < 2 mmol kg −1) salinity-corrected DIC (DIC Surf *) during midsummer. The greater Chl Surf accumulation and DIC Surf * depletion was attributed to an earlier growing season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of these wind-driven mechanisms on Chl Surf and DIC Surf * depended on the extent of sea ice area (SIA) during winter. Winter SIA affected phytoplankton blooms by changing the upper mixed layer depth (UMLD) during the subsequent spring and summer (December-January-February). Midsummer DIC Surf * was not related to DIC Surf * concentration during the previous summer, suggesting an annual replenishment of surface DIC during fall/winter and a relatively stable pool of deep (>200 m depth) "winter-like" DIC on the WAP.

The Southern Ocean is a climatically sensitive region that plays an important role in the regional and global modulation of atmospheric CO 2. Based on satellite-derived sea ice data, wind and cloudiness estimates from numerical models (National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis), and in situ measurements of surface (0-20 m depth) chlorophyll a (Chl Surf) and dissolved inorganic carbon (DIC Surf) concentration, we show sea ice concentration from June to November and spring wind patterns between 1979 and 2006 had a significant influence on midsummer (January) primary productivity and carbonate chemistry for the Western Shelf of the Antarctic Peninsula (WAP, 64°-68°S, 63.4°-73.3°W). In general, strong (>3.5 m s −1) and persistent (>2 months) northerly winds during the previous spring were associated with relatively high (monthly mean > 2 mg m −3) Chl Surf and low (monthly mean < 2 mmol kg −1) salinity-corrected DIC (DIC Surf *) during midsummer. The greater Chl Surf accumulation and DIC Surf * depletion was attributed to an earlier growing season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of these wind-driven mechanisms on Chl Surf and DIC Surf * depended on the extent of sea ice area (SIA) during winter. Winter SIA affected phytoplankton blooms by changing the upper mixed layer depth (UMLD) during the subsequent spring and summer (December-January-February). Midsummer DIC Surf * was not related to DIC Surf * concentration during the previous summer, suggesting an annual replenishment of surface DIC during fall/winter and a relatively stable pool of deep (>200 m depth) "winter-like" DIC on the WAP.

Ocean acidification (OA) is a serious consequence of climate change with complex organism-to-ecosystem effects that have been observed through field observations but are mainly derived from experimental studies. Although OA trends and the resulting biological impacts are likely exacerbated in the semi-enclosed and highly populated Mediterranean Sea, some fundamental knowledge gaps still exist. These gaps are at tributed to both the uneven capacity for OA research that exists between Mediterranean countries, as well as to the subtle and long-term biological, physical and chemical interactions that define OA impacts. In this paper, we systematically analyzed the different aspects of OA research in the Mediterranean region based on two sources: the United Nation’s International Atomic Energy Agency’s (IAEA) Ocean Acidification International Coordination Center (OA-ICC) database, and an extensive survey. Our analysis shows that 1) there is an uneven geographic capacity in OA research, a...

Measurements of the CO 2 system parameters in the Mediterranean Sea are relatively scarce and not representative for all its sub-basins. High quality data collected on May 2013 during the 2013 MedSeA cruise covering the whole basin were used to provide for the first time linear relationships estimating the total alkalinity (A T) and the total dissolved inorganic carbon (C T) from salinity in each Mediterranean basin and sub-basin at different depth layers. These correlations show that a substantial quantity of alkalinity is added to the seawater during its residence time in the Mediterranean Sea, whereas the biological processes, the air-sea exchange and the high remineralization rate are responsible of the high C T concentrations in this sea. Moreover, these fits could be used to estimate the A T and C T from salinity where there are not available measurements of the carbonate system parameters.

River Ocean acidification Gulf of Trieste Adriatic Sea Mediterranean Sea demonstrates a high A T concentration in low salinity surface waters (A T max ¼ 2742.8 mmol kg À1) and a negative A T-salinity correlation. As a result the Gulf of Trieste revealed a low Revelle factor (10.1) and one of the highest buffer capacities of the Mediterranean Sea (ß DIC ¼ 0.31 mmol kg À1), which allows the system to store a significant amount of atmospheric CO 2 with a small decrease of seawater pH.

The carbonate system is a vital buffering system that controls the pH of seawater and maintains a healthy environment for marine organisms. As concerns regarding the fate of anthropogenic CO 2 in the oceans are rising, it is becoming increasingly urgent to systematically quantify and understand this system's parameters, particularly in heavily human-impacted areas, such as the Mediterranean Sea. To date, the paucity of time-series stations adopted to monitor the carbonate system in this sea has precluded characterizing the region at an adequate spatial resolution. Here, we present and study the seasonal and annual variability and drivers of the first carbonate system dataset collected for the Lebanese waters, monthly at the upper 80 m between 2012 and 2017 in two timeseries stations offshore the North of Lebanon-Levantine Sub-basin, Eastern Mediterranean Sea. Annual trends were calculated for the non-adjusted and the adjusted carbonate system parameters (an adjustment that reduces the influence of simple-dilution-concentration [SDC] processes on the trends). Our results show high carbonate system inventory [total alkalinity (A T), total dissolved inorganic carbon (C T), and pH] compared to other Mediterranean areas. The obtained trends reflect increasing rates for both A T and C T , only significant at surface for C T (+5 ± 2 µmol.kg-1 .yr-1 ; p<0.05). Whereas annual acidification rates were always significant (i.e. from-0.009 ± 0.004 to-0.0021 ± 0.001 pH units.yr-1 at 0 m and in the upper 80m respectively for pH T25adj). Concomitantly, decreasing trends of the saturation states for both CaCO 3 minerals were calculated (-0.1 ± 0.04 and-0.07 ± 0.02 yr-1 for calcite and aragonite respectively at surface; p<0.05). Moreover, our results showed that SDC processes, together with CO 2 release/invasion and the active overturning circulation, are controlling this system in the Lebanese seawater, Eastern-most Mediterranean Sea. Contrariwise, the increasing trend of total alkalinity, mainly attributed to SDC processes (i.e. riverine inputs, weathering during extreme events, precipitations), may be buffering the observed acidification rate, which could have been worst in case A T in our area was lower.

Measurements of the CO 2 system parameters in the Mediterranean Sea are relatively scarce and not representative for all its sub-basins. High quality data collected on May 2013 during the 2013 MedSeA cruise covering the whole basin were used to provide for the first time linear relationships estimating the total alkalinity (A T) and the total dissolved inorganic carbon (C T) from salinity in each Mediterranean basin and sub-basin at different depth layers. These correlations show that a substantial quantity of alkalinity is added to the seawater during its residence time in the Mediterranean Sea, whereas the biological processes, the air-sea exchange and the high remineralization rate are responsible of the high C T concentrations in this sea. Moreover, these fits could be used to estimate the A T and C T from salinity where there are not available measurements of the carbonate system parameters.

The effects of different physical and biogeochemical drivers on the carbonate system were investigated in a semi-enclosed coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, Northern Adriatic Sea, Mediterranean Sea). Our 2-year time-series showed that a large part of the seasonal carbonate chemistry variation was controlled by the large seasonal change of seawater temperature, though air-sea CO 2 exchange, biological activity (primary production-respiration), and riverine inputs also exerted a significant influence. With the exception of summer, the Gulf of Trieste was a sink of atmospheric carbon dioxide, showing a very strong CO 2 fluxes from atmosphere into the sea (À16.10 mmol m À2 day À1 ) during high wind speed event of north easterly Bora wind. The CO 2 influx was particularly evident in winter, when the biological activity was at minimum and the low seawater temperature enhanced CO 2 solubility. During spring, the drawdown of CO 2 by primary production overwhelmed the CO 2 physical pump, driving a significant decrease of dissolved inorganic carbon (DIC), [CO 2 ], and increase of pH T25 C . In summer the primary production in surface waters occurred with the same intensity as respiration in the bottom layer, so the net biological effect on the carbonate system was very low and the further reduction of seawater CO 2 concentration observed was mainly due to carbon dioxide degassing induced by high seawater temperature. Finally, during autumn the respiration was the predominant process, which determined an overall increase of DIC, [CO 2 ], and decrease of pH T25 C . This was particularly evident when the breakdown of summer stratification occurred and a large amount of CO 2 , generated by respiration and segregated below the pycnocline, was released back to the whole water column. Local rivers also significantly affected the carbonate system by direct input of total alkalinity (A T ) coming from the chemical weathering of carbonate rocks, which dominate the river watershed. Our finding clearly demonstrates a high A T concentration in low salinity surface waters (A T max ¼ 2742.8 mmol kg À1 ) and a negative A T -salinity correlation. As a result the Gulf of Trieste revealed a low Revelle factor (10.1) and one of the highest buffer capacities of the Mediterranean Sea (ß DIC ¼ 0.31 mmol kg À1 ), which allows the system to store a significant amount of atmospheric CO 2 with a small decrease of seawater pH.

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Measurements of the CO 2 system parameters in the Mediterranean Sea are relatively scarce and not representative for all its sub-basins. High quality data collected on May 2013 during the 2013 MedSeA cruise covering the whole basin were used to provide for the first time linear relationships estimating the total alkalinity (A T) and the total dissolved inorganic carbon (C T) from salinity in each Mediterranean basin and sub-basin at different depth layers. These correlations show that a substantial quantity of alkalinity is added to the seawater during its residence time in the Mediterranean Sea, whereas the biological processes, the air-sea exchange and the high remineralization rate are responsible of the high C T concentrations in this sea. Moreover, these fits could be used to estimate the A T and C T from salinity where there are not available measurements of the carbonate system parameters.

This study presents an estimation of the anthropogenic CO 2 (C ANT) concentrations and acidification (ΔpH ¼pH 2013-pH pre-industrial) in the Mediterranean Sea, based upon hydrographic and carbonate chemistry data collected during the May 2013 MedSeA cruise. The concentrations of C ANT were calculated using the composite tracer TrOCA. The C ANT distribution shows that the most invaded waters (460 mmol kg À 1) are those of the intermediate and deep layers in the Alboran, Liguro-and Algero-Provencal Sub-basins in the Western basin, and in the Adriatic Sub-basin in the Eastern basin. Whereas the areas containing the lowest C ANT concentrations are the deep layers of the Eastern basin, especially those of the Ionian Sub-basin, and those of the northern Tyrrhenian Sub-basin in the Western basin. The acidification level in the Mediterranean Sea reflects the excessive increase of atmospheric CO 2 and therefore the invasion of the sea by C ANT. This acidification varies between À 0.055 and À 0.156 pH unit and it indicates that all Mediterranean Sea waters are already acidified, especially those of the Western basin where ΔpH is rarely less than À 0.1 pH unit. Both C ANT concentrations and acidification levels are closely linked to the presence and history of the different water masses in the intermediate and deep layers of the Mediterranean basins. Despite the high acidification levels, both Mediterranean basins are still highly supersaturated in calcium carbonate minerals.

Measurements of the CO 2 system parameters in the Mediterranean Sea are relatively scarce and not representative for all its sub-basins. High quality data collected on May 2013 during the 2013 MedSeA cruise covering the whole basin were used to provide for the first time linear relationships estimating the total alkalinity (A T) and the total dissolved inorganic carbon (C T) from salinity in each Mediterranean basin and sub-basin at different depth layers. These correlations show that a substantial quantity of alkalinity is added to the seawater during its residence time in the Mediterranean Sea, whereas the biological processes, the air-sea exchange and the high remineralization rate are responsible of the high C T concentrations in this sea. Moreover, these fits could be used to estimate the A T and C T from salinity where there are not available measurements of the carbonate system parameters.

River Ocean acidification Gulf of Trieste Adriatic Sea Mediterranean Sea demonstrates a high A T concentration in low salinity surface waters (A T max ¼ 2742.8 mmol kg À1) and a negative A T-salinity correlation. As a result the Gulf of Trieste revealed a low Revelle factor (10.1) and one of the highest buffer capacities of the Mediterranean Sea (ß DIC ¼ 0.31 mmol kg À1), which allows the system to store a significant amount of atmospheric CO 2 with a small decrease of seawater pH.

The physicochemical characteristics of the sediments of Balaklava bay: granulometric composition and fractional composition content of organic and inorganic carbon are considered. The spatial distribution of the main factions of particle size distribution and content of organic carbon (TOC) and calcium carbonate (CaCO 3 ) are investigated. The relationship between the organic and inorganic carbon and particle size distribution of sediments are analyzed. The main formation factors of the sediments from Balaklava bay are hightlighted. The results of the performed investigations have shown that the bottom deposits in the Balaklava Bay are represented mainly by silts and in some areas the gravel and sandy materials are interspersed. On average, for all the stations the fine-dispersed fraction content makes up 61%. The coarse-dispersed material is concentrated near the coast, and at the bay exit; the increased content of the sand fraction is typical for the central part of the water area. The calcium carbonate content in the Balaklava Bay varies within 18.32-82.95 %; its average value constitutes 40.06%. Its maximum concentrations are in the coastal parts of the bay. The highest correlation between the inorganic carbon content and the granulometric composition in the samples is observed in the coarse-dispersed material (fraction 2-1 mm). As for the fine-dispersed material, the sandy and alevrite-pelite silts are characterized by the inverse relation: from 0.4 -for the fraction 0.25-0.1 mm up to 0.6 for the fraction lower than 0.05 mm. The organic carbon content varies from 0.66 to 4.74%; the average value is 2.37 %. The presence of the increased values in the central part of the bay can be explained by "weak" water exchange formed by minimum wind and wave effect and insignificant eddy formations.

The physicochemical characteristics of the sediments of Balaklava bay: granulometric composition and fractional composition content of organic and inorganic carbon are considered. The spatial distribution of the main factions of particle size distribution and content of organic carbon (TOC) and calcium carbonate (CaCO 3) are investigated. The relationship between the organic and inorganic carbon and particle size distribution of sediments are analyzed. The main formation factors of the sediments from Balaklava bay are hightlighted. The results of the performed investigations have shown that the bottom deposits in the Balaklava Bay are represented mainly by silts and in some areas the gravel and sandy materials are interspersed. On average, for all the stations the fine-dispersed fraction content makes up 61%. The coarse-dispersed material is concentrated near the coast, and at the bay exit; the increased content of the sand fraction is typical for the central part of the water area. The calcium carbonate content in the Balaklava Bay varies within 18.32-82.95 %; its average value constitutes 40.06%. Its maximum concentrations are in the coastal parts of the bay. The highest correlation between the inorganic carbon content and the granulometric composition in the samples is observed in the coarse-dispersed material (fraction 2-1 mm). As for the fine-dispersed material, the sandy and alevrite-pelite silts are characterized by the inverse relation: from 0.4-for the fraction 0.25-0.1 mm up to 0.6 for the fraction lower than 0.05 mm. The organic carbon content varies from 0.66 to 4.74%; the average value is 2.37 %. The presence of the increased values in the central part of the bay can be explained by "weak" water exchange formed by minimum wind and wave effect and insignificant eddy formations.

Sampling of the carbonate system parameters was included to the routine sampling at the POSEIDON-E1-M3A site for the period October 2011-December 2013, aiming to illustrate the present day conditions of carbonate chemistry and establish critical baselines necessary to track further acidification. The presented time-series data exhibited important seasonal variability depicting the ultra-oligotrophic character of the S. Aegean open waters. The minor impact of biological activity on CT variability in the upper layer of the S. Aegean Sea was demonstrated. The scarceness and/or lack of relevant data in the parameterization process of the existing relationships in the literature led to inadequate retrieval of the measured ΑT concentrations.

It is shown that the highest pCO2 and TCO2 variability on a small time scale is observed during the seawater spring warming resulted from the upwelling impact. The diurnal variations of both values (in course of the analogous period) demonstrate no pronounced tendencies; they are characterized by significant inter-annual variability. In course of summer and autumn-winter hydrological seasons, the diurnal variation of pCO2 and TCO2 is insignificant. The minimum values of TCO2 are observed in summer and autumn-winter, whereas the maximum ones – in spring during upwelling. pCO2 value in seawater reaches its maximum in late spring and minimum – in late autumn – early winter hydrological season. During the cold season, the lower pCO2 is characteristic of seawater and the higher one – of the atmosphere. Complex character of pCO2 temporal variability testifies to heterogeneity and different intensity of the factors influencing this value in different seasons. Keywords: equilibrium partial pressure of carbon dioxide (pCO2), total dissolved inorganic carbon (TCO2), diurnal variation of pCO2 and TCO2, inter-diurnal changes of pCO2 and TCO2, seasonal variations of pCO2 and TCO2, the Black Sea coastal waters, upwelling. Sea areas are among the objects, considering within the framework of study of global carbon cycle in the terrestrial biosphere, which deserve special attention. For obtaining more accurate assessment of separated areas contribution to the transport and transformation processes of inorganic carbon compounds, we zone them basing on different criteria. This is carried out due to inhomogeneity of biochemical characteristics of the seas and oceans. Sea area structure includes relatively homogeneous zones. Within them biochemical and other water parameters change insignificantly, or their changes are defined by the known patterns which are characteristic of the considered zones only. Distinguishing of sea and ocean shelf areas is due to specificity of their biochemical characteristics. With a relatively small area (slightly more than 7 % of the entire ocean surface area), these zones significantly contribute to the process of carbon dioxide (CO2) exchange between hydrosphere and atmosphere. According to existing assessments, more than 21 % of total CO2 sink from the atmosphere to the ocean falls on shelf water areas [1, 2]. The role of coastal regions in CO2 transport is conditioned by high intensity of biochemical processes in these zones. Inhomogeneity of shelf areas (in comparison with open water area parts) is their distinctive feature. The features of hydro-chemical coastal water composition are affected by a number of factors: continental runoff, biogeochemical processes in the surf zone and anthropogenic activity. Vertical mixing of water, currents and biota impact [3] also make their contribution. Due to small volume of coastal waters (less than 1 % of the World Ocean overall volume [1]), the change of their chemical composition (including the equilibrium shift between the carbonate system components) is highly dynamic.

The carbonate system is very important since it regulates the pH of the seawater and controls the circulation of CO2 between the various natural reservoirs. Recently, several oceanographic cruises have been carried out to assess this system in the Mediterranean Sea. However, the measurements undertaken to quantify the carbonate system parameters in the Levantine Sub-basin remain scarce and occasional. In our study, we are compiling the occasional data taken near Lebanon and surveying the carbonate system in the Lebanese seawaters for the first time by fixing two stations off the Lebanese coast to study the monthly and annual variations of this system through the water column. The dominant processes changing the carbonate chemistry of a seawater can be described by considering changes in the total alkalinity (AT) and the total dissolved inorganic carbon (CT). To measure these parameters, the collected seawater samples are titrated via potentiometric acid titration using a closed cell (DOE, 1994). Further, the temperature and the salinity are measured in situ. Dissolved oxygen concentrations are measured using a Winkler iodometric titration. Nutrients (phosphates, nitrates, nitrites), chlorophyll a and phytoplankton populations are also studied. The compilation of the carbonate system data taken from the cruises conducted near Cyprus (MedSeA 2013, Meteor 84-3, BOUM, Meteor 51-2) indicate that the AT and CT averages are equal to 2617 ±15 and 2298 ± 9 µmol kg-1 respectively, showing high AT and CT concentrations compared to those measured in other Mediterranean sub-basins. Our survey will provide a brand new dataset that will be useful to better comprehend the carbonate system in the Mediterranean Sea in general and the actual situation of the water masses formation in the Levantine Sub-basin after the Eastern Mediterranean Transient (EMT) in particular. Moreover, this work will permit us to estimate the air-sea fluxes and to estimate the anthropogenic CO2 concentrations and the acidification rate in the Lebanese seawaters for the first time.

Проведена экспертная оценка качества данных за период 1932 − 1993 гг. По ним рассчитана карбонатная система аэробной зоны Черного моря. Выполнена оценка внутригодовых и многолетних изменений карбонатной системы глубоководной части моря за период 1960 –
1993 гг. Дано объяснение внутригодовых изменений карбонатной системы в различных слоях аэробной зоны. Показаны многолетние изменения в значениях pH, общей щелочности и соотношениях компонентов карбонатной системы. Выявлены и объяснены наблюдающийся рост концентрации ТСО2, СО2 и равновесного рСО2, снижение рН и концентрации СО32- вод аэробной зоны Черного моря.

This study presents an estimation of the anthropogenic CO2 (CANT) concentrations and acidification (ΔpH=pH2013–pHpre-industrial) in the Mediterranean Sea, based upon hydrographic and carbonate chemistry data collected during the May 2013 MedSeA cruise. The concentrations of CANT were calculated using the composite tracer TrOCA. The CANT distribution shows that the most invaded waters (>60 µmol kg−1) are those of the intermediate and deep layers in the Alboran, Liguro- and Algero-Provencal Sub-basins in the Western basin, and in the Adriatic Sub-basin in the Eastern basin. Whereas the areas containing the lowest CANT concentrations are the deep layers of the Eastern basin, especially those of the Ionian Sub-basin, and those of the northern Tyrrhenian Sub-basin in the Western basin. The acidification level in the Mediterranean Sea reflects the excessive increase of atmospheric CO2 and therefore the invasion of the sea by CANT. This acidification varies between −0.055 and −0.156 pH unit and it indicates that all Mediterranean Sea waters are already acidified, especially those of the Western basin where ΔpH is rarely less than −0.1 pH unit. Both CANT concentrations and acidification levels are closely linked to the presence and history of the different water masses in the intermediate and deep layers of the Mediterranean basins. Despite the high acidification levels, both Mediterranean basins are still highly supersaturated in calcium carbonate minerals.

Measurements of the CO 2 system parameters in the Mediterranean Sea are relatively scarce and not representative for all its sub-basins. High quality data collected on May 2013 during the 2013 MedSeA cruise covering the whole basin were used to provide for the first time linear relationships estimating the total alkalinity (A T) and the total dissolved inorganic carbon (C T) from salinity in each Mediterranean basin and sub-basin at different depth layers. These correlations show that a substantial quantity of alkalinity is added to the seawater during its residence time in the Mediterranean Sea, whereas the biological processes, the air-sea exchange and the high remineralization rate are responsible of the high C T concentrations in this sea. Moreover, these fits could be used to estimate the A T and C T from salinity where there are not available measurements of the carbonate system parameters.

Ocean acidification had become a major concern for marine scientists, thus a major field in marine sciences. This poster presents the context, objectives, study area, methodology and the preliminary results of an ongoing study aiming to assess the distribution of the carbonate system properties in the Mediterranean Sea, to estimate the anthropogenic carbon dioxide (CANT) concentrations in the water columns of this sea and to evaluate the actual situation of acidification in this sea under the excessive anthropogenic pressure in the Mediterranean area basing on the 2013 MedSeA data cruise.