Investigating the contribution of Seychelles’ seagrass meadows to marine carbon sequestration

Details

Supervisors

Hanert, Emmanuel

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

The oceans are a key component of the climate system. They cover about 72% of the Earth’s surface and have already absorbed about 40% of the carbon that was emitted by human activities since the 19th century. Coastal ecosystems, such as seagrass meadows and mangroves, play a particular role in this blue carbon budget. They have the potential to capture carbon and to store it in deep reservoirs where it will remain for hundreds of years. This carbon sequestration potential remains however poorly understood and unquantified for most coastal ecosystems in the World. Here, we try to estimate the carbon sequestration potential of seagrass meadows on the Seychelles plateau. Seychelles has been developing extensively its blue economy and is keen to estimate the carbon offsetting capacity of its marine ecosystem. We develop a high-resolution ocean circulation model of Seychelles plateau and simulate ocean currents over 3-year period (2018- 2020). These currents are then used to simulate the transport of virtual seagrass fragments from the different confirmed and potential meadows present on the plateau. Our results suggest that most of the seagrass meadows export a large fraction (>80%) of their fragments outside of the plateau, where the carbon contained in the fragments can settle to >1000m depth. We estimate that ~6% of Seychelles seagrass meadows net primary production could be sequestrated in the deep ocean. This corresponds to ~85 tC/yr for confirmed meadows and ~7994 tC/yr for potential meadows. These estimates should help Seychelles quantify its global contribution toward net- zero emissions, as envisaged by the Paris Agreement on climate change.