Blue Carbon in a Sub-Antarctic Marine Protected Area: Current and Future Perspectives

Carbon fixation, storage, and eventual sequestration by marine ecosystems are known as “blue carbon”. This carbon uptake by the oceanic biological pump reduces atmospheric carbon dioxide (CO ₂ ) and is a major negative feedback mechanism to climate change. Benthic assemblages and their related Nature Contributions to People in Namuncurá – Burdwood Bank I and II (BB), two offshore sub-Antarctic Marine Protected Areas (MPAs), are the conservation values of these MPAs. Here, we show that the C reservoirs of these MPAs can be greater than those of their Antarctic counterparts, which, together with their extension, highlights their relevance. Organic and inorganic carbon were measured in the sediments and macrozoobenthic assemblages. More carbon was stored in the sediments than in the macrobenthic organisms, and the inorganic fraction largely exceeded the organic fraction. Most carbon assessments have focused only on the organic fraction, probably due to the complexity of processes involved in CaCO ₃ deposition, which starts releasing CO ₂ . We compare various approaches for incorporating carbonates into carbon estimation and underscore the need to consider them because of their high abundance. Additionally, this work highlights the importance of sub-Antarctic benthic ecosystems as nature-based solutions to climate change.