OOS2025-115, updated on 26 Mar 2025
https://doi.org/10.5194/oos2025-115
One Ocean Science Congress 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Intercomparison and distribution of pHT in the Bosphorus Strait and Black Sea
Rémi Courson1, Agathe Laës-Huon1, Romain Davy1, Florence Salvetat1, Emina Mamaca2, Hasan Örek3, Koray Özhan3, and Mustafa Yücel3
Rémi Courson et al.
  • 1Ifremer, Detection, Sensors and Measurements Laboratory, RDT Research and Technological Development, F‐29280 Plouzané, France
  • 2Ifremer, European and International Affair Direction, DAEI, F‐29280 Plouzané, France
  • 3Middle East Technical University, Institute of Marine Sciences, P.O.Box 28, 33731, Erdemli, Mersin, Türkiye

Understanding and predicting pH distributions through accurate and certified in situ detection is currently crucial. As part of the European BRIDGE Black Sea project, surface pHT transects were carried out in July 2024 across the Marmara Sea, the Bosphorus Strait and the southern Black Sea. This study compares high-resolution temporal pHT measurements from 3 sensors deployed in parallel: SAMI-pHTM (Sunburst Sensors, LLC, colorimetric sensor [1]), SeaFET™ (Sea-Bird Scientific, ion selective field effect transistor (ISFET) [2]) and pHNX (Ifremer Homemade colorimetric sensor). The sensors continuously monitored pHT distributions of surface seawater passing through a SeaBird Scientific SBE45 thermosalinograph. Data collected by SAMI-pHTM (n=319), SeaFET™(n=8424) and pHNX (n=488) were corrected from salinity and temperature (data provided by SBE45 thermosalinograph). Additionally, the SeaFETTM sensor underwent evaluation and correction against robust benchtop measurements, with a one-point correction from the pHNX sensor, ensuring full traceability to international system unit [3]. The three instruments recorded the highest pHT values (8.2225 for pHNX) at the exit of the Bosphorus Strait, extending in a north-easterly direction into the Black Sea. The lowest surface values were obtained in the northern part of the transect (8.1360 for pHNX, 41°33'04.7"N 29°39'01.1"E) and in the Marmara Sea (8.0623 for pHNX, 40°48'49.3"N 28°53'58.6"E). These findings are in line with a previous study carried out in the same area in June 2023 (data not published yet), and the general trend towards the entry of a pH-enriched flow into a semi-enclosed sea has been observed in other parts of the world [3].

Figure 1: pHT sensors and sample inlet

Figure 2: Distribution of pHT from pHNX

[1] A. M. Nightingale, A. D. Beaton, and M. C. Mowlem, “Trends in microfluidic systems for in situ chemical analysis of natural waters,” Sensors Actuators B Chem., vol. 221, pp. 1398–1405, 2015.

[2] T. R. Martz, J. G. Connery, and K. S. Johnson, “Testing the Honeywell Durafet® for seawater pH applications,” Limnol. Oceanogr. Methods, vol. 8, no. MAY, pp. 172–184, 2010.

[3] X. Liu, Z. A. Wang, R. H. Byrne, E. A. Kaltenbacher, and R. E. Bernstein, “Spectrophotometric measurements of pH in-situ: Laboratory and field evaluations of instrumental performance,” Environ. Sci. Technol., vol. 40, no. 16, pp. 5036–5044, 2006.

 

How to cite: Courson, R., Laës-Huon, A., Davy, R., Salvetat, F., Mamaca, E., Örek, H., Özhan, K., and Yücel, M.: Intercomparison and distribution of pHT in the Bosphorus Strait and Black Sea, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-115, https://doi.org/10.5194/oos2025-115, 2025.