Bergen mesocosm experiment 2011

Gisle Nondal, Richard Bellerby, Anna Silyakova, Helene Frigstad and Emanuele Reggiani

London 29.09.11

Raunefjorden, Norway

• 9 mesocoms deployed and moored

• each 25 m long with a volume of ca. 75 m3

• Initially open at top and bottom

• covered by nets with 3 mm mesh size

• enclosed water exchanging for 3 days

(Courtesy of Ulf Riebesell, IFM-GEOMAR)

Set-up

3 mesocosms moored in a rowWith anchor weights at each end

anchor weights (old railway wheels)

set of 3 mesocosms

(Courtesy of Ulf Riebesell, IFM-GEOMAR)

Target fCO2

1 2 3 4 5 6 7 8 9 180 280 390 560 840 1120 1400 2000 3000 µatm glacial pre- present 2x p.i. 3x p.i. 4x p.i. 5x p.i. industrial

CO2 Enrichment

(Courtesy of Ulf Riebesell, IFM-GEOMAR)

After 3 days:

•Closing sediment traps

•Pulling up upper bags

•Adding salt (volume determination)

•Homogenizing

•CO2 enrichment (in 4 steps)

•Nutrient addition (once)

(Courtesy of Ulf Riebesell, IFM-GEOMAR)

Sampling procedure:

Sampling at the Mesocoms with zodiacs

Gas samples directly taken on “Wassermann”

Integrating water sampler

Carbonate chemistry In situ measurements of:

Total inorganic carbon (DIC)

DIC= [CODIC= [CO22(aq)]+[H(aq)]+[H22COCO33]+[HCO]+[HCO33--]+[CO]+[CO33

2-2-]]

Total alkalinity

AAtt=[HCO=[HCO33--] +2[CO] +2[CO33

2-2-]+[B(OH)]+[B(OH)44--]+ [OH]+ [OH--]+[HPO]+[HPO44

22]+2[PO]+2[PO4433]+ ]+

[SiO(OH)[SiO(OH)33--]+ [HS]+ [HS--]+[NH]+[NH33]-[H]-[H++]-[HSO]-[HSO44

--]-[HF]-[H]-[HF]-[H33POPO44] ]

pH

pH = -log[HpH = -log[H++]]

Overdetermination!!