Oceanic Carbon in Seagrass Ecosystems in Freshwaters of Northern Brazil

Abstract Seagrass ecosystems can sequester and retain considerable amount of oceanic carbon. However, few studies and limited data constrain seagrass carbon stocks on regional and global scales, especially in underreported seagrass region of South America. This study measured and predicted carbon stocks in seagrass beds of the Macapa River and the Barra Grande lagoon, northern Brazil. Aboveground and belowground biomass components were sampled from Halodule wrightii seagrass beds of the Macapa River only, while sediment cores were sampled at 50cm depth in the Halodule wrightii seagrass beds of the Macapa River. In Barra Grande lagoon, three sediment cores were sampled at 8-30cm depth in Halodule wrightii and mixed stands of Halodule sp. seagrass beds. The carbon (C) stocks of the seagrass aboveground and belowground biomass of Halodule wrightii seagrass beds of the Macapa River were 0.005MgC/ha− 1 and 0.018MgC/ha− 1 respectively. The C stock of sediment from seagrass beds in Macapa River averaged 41.8MgC/ha− 1, while the C stock of sediment from seagrass beds of Barra Grande lagoon averaged 12.3MgC/ha− 1, These findings add to the limited global database on seagrass carbon stocks to support optimization of carbon capture and storage through sustainable global carbon financing regime for vegetated marine ecosystems. The results also contributes to realizing SDG 13 indicator 13.2.2 on reducing the total annual greenhouse gas (GHG) emissions, SDG 14.2 target, namely, “By 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans.”