Atmospheric CO2 has risen from 280 micro-atmospheres during preindustrial times to 370 micro-atmospheres today. This is predicted to double over the next 100 years if anthropogenic emissions of CO2 continue at their current rate. The microscopic marine algae (the phytoplankton), are able to fix CO2 through photosynthesis and can therefore reduce atmospheric CO2 by drawing it down into the ocean. Photosynthesis involves a series of enzymatic controlled reactions that start with capturing light energy and finish with fixing CO2 to build phytoplankton cells. Some of the fixed carbon is lost through respiration. Marine bacteria, the microscopic animals known as the zooplankton and phytoplankton themselves during the night time respire. The extent to which phytoplankton photosynthesize and fix carbon and the bacteria-zoophytoplankton (or marine plankton) community respires carbon controls whether CO2 is drawn down from the atmosphere to the ocean or is released to the atmosphere from the ocean. The overall objective of this proposal is to improve our understanding of how the marine plankton community in the South Atlantic and the coast of Brazil potentially regulate the atmospheric CO2 concentration. Phytoplankton carbon fixation can be monitored from space using satellite sensors. A new satellite sensor, that has the capability to do this, will be launched by the European Space Agency in autumn 2015. We will use data from this new satellite to study this phenomena in collaboration with a Brazilian Research Institute. The results will benefit both UK and Brazilian research on climate change. The RCUK-FAPESP Lead Agency Agreement is being applied by the applicants