There is a general belief that the magnitude of ocean acidification can sufficiently be quantified from the atmospheric pCO2 levels and the CO2 exchange between seawater and the atmosphere. This is approximately true for oceanic waters. However, it is not the case for coastal seas because several other processes and mechanisms are influencing the seawater pH. These form the so called acid-base system – a complex net of interrelationships between chemical species and processes that control the seawater pH. At present, the knowledge on the structure and functioning of the acid-base system contains a lot of gaps and/or shortcomings, which lead to wrong conclusions and questionable predictions of the future pH development. Since the CO2 system is an integral part of the acid-base system, it is impossible to understand the CO2 system and to assess processes such as the CO2 gas exchange or calcium carbonate dissolution/formation, without a clear
idea about the structure and functioning of the whole acid-base system. In this context the Baltic Sea can be considered as a test field because on one hand the low buffer capacity makes the Baltic Sea vulnerable to acidification, and on the other hand the sea is exposed to various anthropogenic influences which have the potential to change the acid-base system.
Karol K., Bernd S., Beata S., Karoline H., Aleksandra W., Marcin S. & Katarzyna K., 2016. Peculiarities of the Baltic Sea acid-base system. In Reckermann M. & Köppen S. (Eds.), Multiple drivers for Earth system changes in the Baltic Sea region, 1st Baltic Earth Conference, International Baltic Earth Secretariat Publication No. 9, June 2016, pp. 42-43. Article.
