Factors influencing the acid–base (pH) balance in the Baltic Sea: a sensitivity analysis

Abstract

A B S T R A C TUsing calculations based on the marine carbon system and on modelling, the sensitivity of Baltic Sea surface pH was examined. Transient long-term calculations demonstrated that the marine carbon system adjusts to lateral boundary conditions within some decades, as does salinity. Climate changes in temperature or salinity will only marginally affect the acid-base (pH) balance. Wetter or dryer climate will also play a minor role in the pH balance. The direct effect on seawater pH of acid precipitation over the Baltic Sea surface was demonstrated to be small. Acidification due to river transport of dissolved organic carbon (DOC) into the marine system seems marginal although mineralization of terrestrial DOC may cause extra marine acidification, but the effect has yet to be quantified. Increased nutrient load may increase the amplitude in the pH seasonal cycle and increase the acidification during winter time. Fossil fuel burning is likely to have both a direct and indirect effect through increased CO 2 levels, altering seawater pH as well as changing the river chemistry. This may severely threaten some species in the Baltic Sea, particularly in the Northern Baltic.

Long-term monitoring data reveal pH dynamics, trends and variability in the western Gulf of Finland

“…The CO2 emissions are suggested to be the major factor underlying the observed changes in the oceans (Santana-Casiano et al 2007, Wootton et al 2008, Olafsson et al 2009, Omstedt et al 2010, Provoost et al 2010. Without CO2 measurements, we cannot say if CO2 in surface waters is responsible for the pH decrease in the Gulf of Finland.…”

“…Many studies present models of future ocean pH, whereas relatively few papers present measured pH data (Santana-Casiano et al 2007, Wootton et al 2008, Olafsson et al 2009, Omstedt et al 2010, Provoost et al 2010. The aim of the present study is to demonstrate pH dynamics and its variability, and whether pH shows a decreasing trend in the Gulf of Finland since the beginning of the 1970s until today.…”

Future changes in the Baltic Sea acid–base (pH) and oxygen balances

“…C org terr loads from individual catchments have moreover been found to differ markedly depending on land use and vegetation cover (Humborg et al, 2004). The marine carbon system has been introduced into some Baltic Sea model studies (Leinweber et al, 2005;Kuznetsov et al, 2008;Omstedt et al, 2009Omstedt et al, , 2010Gustafsson, 2012;Edman and Omstedt, 2013). Kuznetsov et al (2008) and Leinweber et al (2005) have focused on the modelling of nitrogen fixation during plankton blooms.…”

How will Ocean Acidification Affect Baltic Sea Ecosystems? An Assessment of Plausible Impacts on Key Functional Groups

“…Closer to shore the effects of atmospheric CO 2 on coastal seawater pH are complicated by local effects of run-off, eutrophication, upwelling, atmospheric deposition and remineralisation, all of which also influence local biogeochemistry (Doney et al 2007;Omstedt et al 2009Omstedt et al , 2010. Consequently, coastal pH is more variable and difficult to predict than that of the open ocean (Andersson et al 2005).…”