Acidification indicators for the Baltic Sea Jacob Carstensen, Bo - - PowerPoint PPT Presentation

Jacob Carstensen, Bo Gustafsson, Gregor Rehder

Acidification indicators for the Baltic Sea

Ocean versus coastal acidification

Doney et al. (2010) Science Duarte et al. (2013) ESCO

The simple concept of ocean acidification does not apply to coastal ecosystems

Many different processes affect pH in the coastal zone

• Catchment characters affecting inputs from land

(weathering, mining, liming, etc.)

• Atmospheric

deposition

• Eutrophication
• Metabolism
• CO2 exchange with

the atmosphere

• Warming

Baltic Sea trends in pH

7.2 7.6 8.0 8.4 8.8 1950 1960 1970 1980 1990 2000 2010 2020 pH Laajalahti, Baltic Sea 7.6 7.8 8.0 8.2 8.4 1950 1960 1970 1980 1990 2000 2010 2020 pH Gotland Basin, Baltic Sea 7.8 8.0 8.2 8.4 1950 1960 1970 1980 1990 2000 2010 2020 pH Bornholm Basin, Baltic Sea

Baltic Sea trends in pH

7.0 7.2 7.4 7.6 1950 1960 1970 1980 1990 2000 2010 2020 pH Kemi, Baltic Sea 7.4 7.6 7.8 8.0 8.2 8.4 1950 1960 1970 1980 1990 2000 2010 2020 pH Bothnian Bay, Baltic Sea 7.6 7.8 8.0 8.2 8.4 1950 1960 1970 1980 1990 2000 2010 2020 pH Bothnian Sea, Baltic Sea

Baltic Sea trends in pH

7.6 7.8 8.0 8.2 8.4 1950 1960 1970 1980 1990 2000 2010 2020 pH Mariager Fjord, Danish Straits 7.4 7.6 7.8 8.0 8.2 8.4 8.6 1950 1960 1970 1980 1990 2000 2010 2020 pH The Sound, Danish Straits 7.6 7.8 8.0 8.2 8.4 8.6 1950 1960 1970 1980 1990 2000 2010 2020 pH Kattegat, Danish Straits

Increasing alkalinity might buffer against acidification

Raymond & Cole (2003) Science Duarte et al. (2013) ESCO

Mississippi River Ohio River

Spatial and temporal trends in total alkalinity

Central Baltic Sea

Müller et al (2016) Limnol Oceanogr

Alkalinity trends – adjusted for salinity

Müller et al (2016) Limnol Oceanogr

A look at three different estuaries with long-term data on pH and alkalinity

• Shallow
• pH from

6.1 to 10

• AT from

0.6 to 3.4 mmol kg-1

• Different

end- members

Carstensen et al (Subm.) GBC

Roskilde Fjord receives freshwater with high pH and alkalinity

6 7 8 9 10 5 10 15 20 25 30 35 pHTOT Salinity Boundary Inside Roskilde Fjord C) 1.5 2.0 2.5 3.0 3.5 4.0 5 10 15 20 25 30 35 Alkalinity (mmol kg-1) Salinity Boundary Inside Roskilde Fjord D)

Carstensen et al (Subm.) GBC

Skive Fjord end-members are similar

6 7 8 9 10 5 10 15 20 25 30 35 pHTOT Salinity Boundary Inside Skive Fjord E) 0.5 1.0 1.5 2.0 2.5 3.0 5 10 15 20 25 30 35 Alkalinity (mmol kg-1) Salinity Boundary Inside Skive Fjord F)

Carstensen et al (Subm.) GBC

Changes in pH (observed and adjusted for sali/temp effects on carbonate speciation)

7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 J F M A M J J A S O N D pHTOT Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord A) 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 1970 1980 1990 2000 2010 2020 pHTOT Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord P=0.0080 P=0.0011 P<0.0001 P<0.0001 B) 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 J F M A M J J A S O N D pH adjusted Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 1970 1980 1990 2000 2010 2020 pH adjusted Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord P=0.0317 P=0.0034 P<0.0001 P<0.0001

Alkalinity is not behaving conservatively

Alkalinity source

• Decalcification
• Denitrification and

sulfate reduction

• Nitrate uptake
• Atmospheric deposition

Alkalinity sink

• Calcification

Dilution/concentration by rain

• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6 0.8 J F M A M J J A S O N D Alkalinity residual (mmol kg-1) Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord A)

• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6 0.8 1970 1980 1990 2000 2010 2020 Alkalinity residual (mmol kg-1) P=0.0070 P=0.0013 P=0.8197 P=0.5268 B)

Other components of the carbonate system

0.0 0.5 1.0 1.5 2.0 2.5 3.0 1970 1980 1990 2000 2010 2020 DIC (mmol kg-1) D) P<0.0001 P=0.0292 P=0.0040 P=0.0607 500 1000 1500 2000 1970 1980 1990 2000 2010 2020 pCO2 (µatm) F) P<0.0001 P=0.0009 P=0.0014 P<0.0001 0.0 0.5 1.0 1.5 2.0 2.5 3.0 J F M A M J J A S O N D DIC (mmol kg-1) Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord C) 1000 2000 3000 4000 J F M A M J J A S O N D pCO2 (µatm) Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord E)

Estuarine effects on biology and climate

1 2 3 4 5 J F M A M J J A S O N D ΩAragonite Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord G) 2 4 6 8 J F M A M J J A S O N D ΩCalcite I) 1000 2000 3000 4000 J F M A M J J A S O N D pCO2 (µatm) Ringkøbing Fjord (1980-1995) Ringkøbing Fjord (1996-2016) Roskilde Fjord Skive Fjord E)

Massive colonisation by Mya arenaria occurred despite low Ω-values Possible physiological effects from high extracellular pCO2 Net sources of CO2 to the atmosphere

Summary and discussion points

• The Baltic Sea exhibits quite variable pH trends –

different from ocean acidification

• Enhanced alkalinity input may buffer acidification
• Changes in pH is mainly an indicator of the

balance between production and respiration

• Monitoring pH and alkalinity is relatively

inexpensive and provides important insight into carbon cycling