Processes of coastal ecosystem carbon sequestration and approaches for increasing carbon sink

The oceans are the largest carbon pools on Earth, and play the role of a buffer in climate change. Blue carbon, the carbon (mainly organic carbon) captured by marine ecosystems, is one of the important mechanisms of marine carbon storage. Blue carbon was initially recognized only in the form of visible coastal plant carbon sequestration. In fact, microorganisms (phytoplankton, bacteria, archaea, viruses, and protozoa), which did not receive much attention in the past, account for more than 90% of the total marine biomass and are the main contributors to blue carbon. Chinese coastal seas, equivalent to 1/3 of China's total land area, have a huge carbon sink potential needing urgently research and development. In this paper, we focus on the processes and mechanisms of coastal ocean's carbon sequestration and the approaches for increasing that sequestration. We discuss the structures of coastal ecosystems, the processes of carbon cycle, and the mechanisms of carbon sequestration. Using the evolution of coastal ocean's carbon sinks in sedimentary records over geologic times, we also discuss the possible effects of natural processes and anthropogenic activities on marine carbon sinks. Finally, we discuss the prospect of using carbon sequestration engineering for increasing coastal ocean's carbon storage capacity.