Future carbon cycling - predicting and understanding coccolithophorid calcification in a changing ocean
Project Team: Kai Schulz, Natasha Gafar, Brad Eyre
Coccolithophores (compare SEM images below) are unicellular calcifying organisms and an important component of the marine phytoplankton assemblage, influencing Earth's carbon cycling for the last 200 million years. Human driven increases in atmospheric carbon dioxide (CO2) are expected to result in significant changes in ocean carbonate chemistry speciation (also known as ocean acidification), temperature, and light and nutrient availability, all of them in combination termed ocean change. Despite this, there is currently a lack of data and understanding on coccolithophore responses to CO2 in combination with these additional environmental factors. Furthermore, of approximately 200 extant species of coccolithophores, the majority of research into the response of coccolithophore physiology to just changes in carbonate chemistry comes from a mere handful of species. As a result of this, our ability to predict how this group will be affected under future climate conditions is significantly limited.
To address this, our project will build on existing data for the coccolithophore Gephyrocapsa oceanica (Image A) to derive a new physiology-based model to describe the response of growth, calcification and photosynthetic carbon fixation rates to changing carbonate chemistry, able to also account for the effects of temperature and light. Extending the available data for the coccolithophore Emiliania huxleyi (Image B) with additional experiments on the interaction of light and carbonate chemistry will then allow comparison of the individual sensitivities of these two key species. This project also aims to expand the currently available knowledge by assessing the response of so far under-studied, oligotrophic coccolithophore species to ocean change.