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Drivers of the carbonate system seasonal variations in a Mediterranean gulf
- Source :
- Estuarine, Coastal and Shelf Science. 168:58-70
- Publication Year :
- 2016
- Publisher :
- Elsevier BV, 2016.
-
Abstract
- 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 (−16.10 mmol m −2 day −1 ) 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 = 2742.8 μmol kg −1 ) 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 (s DIC = 0.31 mmol kg −1 ), which allows the system to store a significant amount of atmospheric CO 2 with a small decrease of seawater pH.
- Subjects :
- 0106 biological sciences
Adriatic Sea
010504 meteorology & atmospheric sciences
Alkalinity
Gulf of Trieste
Aquatic Science
Oceanography
01 natural sciences
chemistry.chemical_compound
Mediterranean sea
Water column
Mediterranean Sea
Buffer capacity
0105 earth and related environmental sciences
River
pH
Ocean acidification
010604 marine biology & hydrobiology
chemistry
Carbon dioxide
Carbonate system
Carbonate
Seawater
Geology
Revelle factor
Subjects
Details
- ISSN :
- 02727714
- Volume :
- 168
- Database :
- OpenAIRE
- Journal :
- Estuarine, Coastal and Shelf Science
- Accession number :
- edsair.doi.dedup.....aef799bdaff03d76c5371597e9e5a3f8