Sphagnum peatlands of Reunion Island: potential and limitations as environmental archives for the Quaternary of the Indian Ocean.

Contrary to temperate and boreal peatlands built after the glacial retreat, tropical peatlands are potentially recording environmental information pre-dating the Holocene. However on tropical volcanic islands, Sphagnum moss are scarce and/or rarely build peat. Within the framework of the several projects on the territory of Reunion Island, we sampled peat bogs and Sphagnum mats of Reunion Island in 2021 (Margenat and Le Roux, 2023). The objectives were originally to use them as microplastic traps and thus reveal the history of atmospheric contamination by microplastics in the Indian Ocean over the last fifty years. It turns out some peat cores are older than expected and can provide amazing archives for the Holocene and Last Glacial environmental history of the Indian Ocean and La Réunion Island itself including the last period of strong volcanic activities. For example, one site located in the heart of the National Park is 25 ky old. In this talk, we will present the diversity of the Sphagnum peatlands of La Réunion, the first results of peat characterization, and the first results of radiometric age dating covering the last glacial maximum, the Holocene, and the most recent periods. We will then discuss potential and limitations of La Réunion peat records in paleo-landscape, paleo-atmosphere and carbon cycle aspects.   References: Margenat, H., Le Roux, G., 2023. POST EXPEDITION REPORT Field Expedition La Réunion Island, France ATMO-PLASTIC Project. Zenodo. https://doi.org/10.5281/zenodo.7643599