Theme 2 - Key Questions

What are the effects of ocean acidification and related changes in seawater chemistry on marine organisms, what are the underlying mechanisms of the observed responses and the potential for adaptation, how are they modulated by other environmental stressors, and what are the consequences for marine ecosystems and ocean biogeochemical cycles?

CO2

Theme 2: Ecosystem impacts, acclimation and adaptation

WP5 WP8 Trophic interactions

Climate relevantgases

Nutrientavailability

Autotrophic processes

WP6Reproduction & growth

WP4-8Adaptation

WP7Microbial activity

WP4Biocalcification

Oceanchemistry

WP9From process studies to ecosystem models

Theme 2 Ecosystem impacts, acclimation and adaptation• WP4 Sensitivity of calcification (D. Iglesias-Rodriguez)• WP5 Sensitivity of autotrophic processes (U. Riebesell)• WP6 Performance: reproduction and growth (H.-O. Pörtner)• WP7 Microbial diversity and activity, in particular nitrogen cycling (J. Middelburg)• WP8 Impact on trophic interactions (F. Thingstad)• WP9 From process studies to ecosystem models (A. Oschlies)

WP 5 Sensitivity of autotrophic processes

Objectives:• Quantify effects of OA on photosynthetic carbon metabolism & nitrogen fixation

• Assess the consequences for elemental stoichiometry, partitioning of organic matter into dissolved & particulate phases, and vertical transport

• Search for changes in gene expression for selected genes relevant for nutrients and carbon metabolism

• Determine effects on the production of climate relevant biogases

• Assess effects on the speciation and bioavailability of major and trace nutrients (Fe, Zn)

Partners: IFM-GEOMAR, AWI, PML, NIOZ, NOC, UiB, UC

WP 5 Sensitivity of autotrophic processesDescription of Work:Determine community level responses to OA of photosynthetic carbon and nitrogen fixation, exudation, partitioning into dissolved and particulate organic matter, stoichiometry, and production of climate relevant biogases in off-shore mesocosm CO2 perturbation experiments (IFM-GEOMAR, UiB, UC, AWI, PML, NIOZ, NOC)

Pelagic mesocosm CO2 enrichment experiment

380

720

550 86010401200

pCO2 (µatm)

WP 5 Sensitivity of autotrophic processesDescription of Work:

CA activity

centrifugationMass spectrometer

PhotosynthesisCO2 / HCO3

-

uptake

180 µmol photons m-2 s-1

15 °C

15 °C

300 µmol Photonen m-2 s-1

36 180 360 1800 ppmv CO2Assess combined effects of acidification and changes in temperature, light, and nutrients on carbon and energy fluxes in key phytoplankton taxa (AWI, IFM-GEOMAR, PML, NIOZ)

Membrane inlet mass spectrometry

Assess combined effects of acidification and changes in temperature, light, and nutrients on carbon and energy fluxes in key phytoplankton taxa (AWI, IFM-GEOMAR, PML, NIOZ)

Model carbon fluxes and energy allocation at the cellular level based on results obtained experimentally (AWI)

WP 5 Sensitivity of autotrophic processesDescription of Work:

Determine expression of selected genes for nutrients and carbon uptake, exudation, and carbonic anhydrase and the influence on gene diversity in (meta)genomic databases in laboratory and mesocosm experiments (IFM-GEOMAR, NIOZ)

Determine changes in the speciation and bioavailability of major and trace nutrients (Fe, Zn) and related effects on photosynthesis and carbon metabolism (NIOZ, NOC)

WP 5 Sensitivity of autotrophic processesDeliverables in first 18 months:• Standardized protocols (for experimental WPs 4, 5, 6, 7, 8) for ensuring internal consistency of the CO2 system in CO2 perturbation studies (month 3; R, PU)

• Methodologies applied in off-shore CO2 perturbation studies, presented at “The Ocean in a high CO2 world” meeting (month 9; O, PU)

• Workshop on protocols for CO2 perturbation experiments (month 12; O, PP)

• Report on OA-related changes in nutrient and trace metal chemistry (month 12; R, PU)

• Comprehensive data sets on off-shore mesocosm CO2 perturbation studies (months 18, O, CO)