Pelagic Ecosystem CO2 Enrichment Study

EU Large-Scale-Facilities, University of Bergen, Norway  

 
 

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To examine effects of ocean acidification on the ecosystem level, three sets of mesocosm CO2 perturbation experiments were conducted in the Large Scale Facilities of the University of Bergen, Norway in 2001, 2003 and 2005. In nine mesocosms covered by gas-tight tents with 95% light transmission CO2 was adjusted through aeration with CO2-enriched or CO2-free air. Initial CO2 concentrations in triplicate mesocosms were set to

  • 190, 380 and 700 ppmV CO2, corresponding to glacial, present and projected year 2100 (IPCC scenario IS92a) levels in 2001 and 2003, and

  • 380, 750, and 1100 ppmV CO2, corresponding to present and projected year 2100 and 2150 levels in 2005.

Phytoplankton blooms dominated by coccolithophores (2001 and 2005) and diatoms (2003) were initiated through variation in nutrient ratios and were closely monitored during bloom development and decline. By covering a wide range of ecosystem parameters, the project was able to distinguish between ecosystem components and processes non-responsive and sensitive to CO2 induced seawater acidification. The project has shown that mesocosm perturbation experiments provide a suitable tool for assessing effects of past and future changes in CO2 concentration on the ecosystem level.

 

 Example: Formation of calcareous platelets in calcifying algae (e.g. Calcidiscus leptoporus) is hampered at elevated CO2 :

 

Today‘s world: pCO2: 280-380 ppmV

 

High-CO2 world: pCO2: 580-720 ppmV