This project makes use of new technology developed by the Max Planck Institute for Marine Microbiology (MPI-MM) and the National Oceanography Centre (NOC). MPI-MM has developed a pH and O2 eddy covariance system and the NOC has developed autonomous in situ sensors to measure carbonate parameters. With these technologies, we will address the fundamental question of how changes in carbonate chemistry within seagrass beds affects community calcification. We will evaluate the effect of diurnal metabolic changes in carbonate chemistry as a driver of calcification, while the effect of ocean acidification will be investigated near CO2 vents. These novel measurements of community calcification will be made at high temporal resolution, at an ecosystem scale (tens of m2), and under in situ environmental conditions.