Impact of nutrient regime on growth and calcification of high-calcifying strains of coccolithophores in the ocean

• Applicant: Dr. Claudia Sprengel, since 7/2005
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: from 2004 to 2006
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5435331

The aim of the present proposal is to provide a basic understanding of coccolithophore nutrient physiology in order to gauge the synergistic effects of decreased nutrient inventories and increased pCO2 on coccolithophorid growth and distribution with future climate change. Modeling efforts suggest a 1-4 K increase in sea surface temperature and predict a substantial increase in stratification, and a concomitant reduction in nutrient inventories, of the upper ocean in the coming century. At the same time, the anthropogenic CO2 concentration is predicted to double. Increased stratification and pCO2 may have opposing effects on calcification, the former increasing the rate of calcification and the latter decreasing it. How these opposing effects will mediate the growth of coccolithophores and phytoplankton community composition will determine the future role of calcifying plankton in deep ocean carbon storage and atmospheric CO2 draw-down. We will investigate the ability of coccolithophores to grow on alternative nutrient sources such as dissolved organic substrates in laboratory experiments, and assess the synergistic effects of pCO2 and varying nutrient ratios in field bioassay experiments in the North Atlantic ocean. the information will be used to calibrate the ecosystem model "REcoM & Co" and to perform model simulations of future coccolithophore distributions.

• DFG Programme: Research Grants
• Ehemalige Antragstellerinnen / Ehemalige Antragsteller: Dr. Gry Mine Berg, until 7/2005; Dr. Klaus Valentin, from 7/2005 until 7/2005