Coccolithophore Culture Laboratory

Coccolithophores represent an important phytoplankton group fixing CO₂ in organic molecules through he photosynthesis and releasing CO₂ during calcification of their calcite plates (coccoliths). The coccoliths are often preserved in the bottom of the ocean in the fossil record. The trace elements and isotopic composition measured in coccoliths have been investigated for its applicability as a proxy for reconstructions of paleoclimate. However, in order to interpret the different elemental composition measured in coccoliths calcite, we need to better understand the biochemistry and physiological processes that modulate intracellular calcification in coccolithophores. Therefore, mechanistic studies of coccolithophore calcification, and in vitro investigation of the effects of climate relevant environmental parameters on the composition of coccolith calcite are essential to produce reliable reconstructions of paleoclimates.

The culture facility consists in a climate room where temperature and humidity are continuously controlled in the room. Inside the climate room will be installed different devices for continuous culturing of coccolithophores: one multicultivator (8 tubes of 80 mL) and two photobioreactors (1000ml vessel). The three systems will be equipped with a LED panel, allowing customized irradiance levels and light:dark cycles, as well as high precision gas mixing systems, which will allow to mimic climate relevant scenarios of atmospheric CO₂.

During incubations different physico-chemical parameter such as temperature, pH, DIC and delta¹³C can be continuously or semi-continuously monitored. In addition, biological parameters such as cell growth, photosystem II quantum yield and chlorophyll a variable fluorescence can be also monitored and, aliquots of the cell culture suspension can be collected and preserved for additional biogeochemical analysis.

The continuous culturing systems require large volumes of seawater, which will be produced in the laboratory in a semi-automatic system. The artificial seawater produced will be chemically characterized, empowering the users to precisely manipulate the composition of the culture medium. Thereby, the coccolithophore culture facility will allow the group to perform a large variety of experiments to investigate biological control on the incorporation of trace elements and isotopes into the coccolith calcite, to investigate the effects of different elements availability on coccolithophores physiology and calcification, to provide parametrization data for climate relevant biogeochemical models, etc.