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SPECTROPHABS: Spectrophotometric pH-measurements for monitoring of marine acidification in the Baltic Sea

Building on the work of the BONUS PINBAL innovation project, SPECTROPHABS will clarify open questions regarding long-term stable and traceable environmental monitoring of the pH value in the Baltic Sea through spectrophotometric pH measurement, and develop a suitable monitoring concept. This will allow to make statements on possible acidification, especially in the German Baltic Sea areas. The long-term goal is the operationalisation of spectrophotometric measurements of the pH-value in the Baltic Sea and thus the establishment of a long-term stable monitoring of the pH-value in a complex brackish water system. To approach this goal i) the currently commercially available devices for spectrophotometric pH measurement in seawater will be tested and evaluated, ii) a strict uncertainty consideration as a function of the influencing variables will be carried out, iii) possibilities for dealing with the problem of the lack of availability of the purified indicator dye meta-cresol purple will be investigated, (iv) routine measurements during monitoring cruises in the Baltic Sea and by using a MARNET station will be demonstrated; and (v) a revision of the corresponding HELCOM guideline for the determination of pH in seawater based on the project results will be proposed.


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  • Rehder, G. and J. M. L. Avila (2023). Spektrophotometrische pH-Messungen zur Überwachung der Meeresversauerung in der Ostsee und zur Unterstützung der Weiterentwicklung des HELCOM- Versauerungsindikators - SPECTROPHABS - Abschlussbericht.IOW BSH. 28 S.,
  • Kuliński, K., G. Rehder, E. Asmala, A. Bartosova, J. Carstensen, B. Gustafsson, P. O. J. Hall, C. Humborg, T. Jilbert, K. Jürgens, H. E. M. Meier, B. Müller-Karulis, M. Naumann, J. E. Olesen, O. Savchuk, A. Schramm, C. P. Slomp, M. Sofiev, A. Sobek, B. Szymczycha and E. Undeman (2022). Biogeochemical functioning of the Baltic Sea. Earth Syst. Dynam. 13: 633-685, doi: 10.5194/esd-13-633-2022