Macroalgal and mangrove provenances demonstrate their relevance in contributing to the blue carbon pool of a tropical seagrass meadow

Abstract

Mangroves, seagrasses and macroalgae form inter-connected coastal habitats.They are involved in the direct and indirect sequestration and accumulation of blue carbon and are recognized for their role in climate change mitigation.Macroalgae, though residing within or in close proximity to these ecosystems are, however, not perceived as contributing to blue carbon storage. Such habitat connectivity among the mangrove, seagrass, and macroalgal compartments complicates a straightforward assessment of blue carbon storage. In this study, we assessed the contributions of these macrophytes as endmembers to the bulk organic carbon (OC) stocks in surficial (top 30 cm) and deep (31-100 cm) sediment layers of seagrass beds within the Sungai Pulai estuary (Malaysia).Organic carbon stocks in the seagrass sediments ranged from 14.3 to 21.4 Mg OC ha À1 (surficial depths), and 137.9 ± 23.3 (mean ± SE) Mg OC ha À1 for the deep layer. Mangrove-derived matter contributed a maximum of 65% to the bulk OC pool. The existence of downcore variability indicated that macroalgae contributed up to 16% and were higher than seagrass sources (12%). Our results suggest that macroalgal-derived and mangrove-derived organic matter are important contributors to OC sequestration in the estuary. In view of the heterogeneous OC pool that contributes to bulk OC stocks, placing importance on only one OC source may construe an incomplete profile of habitat-specific capacity for OC storage. This has wider implications for understanding OC subsidies, the effects of which are particularly relevant when one considers the impacts of coastal land use changes on blue carbon storage.

Seaweed as climate mitigation solution: Categorizing and reflecting on four climate mitigation pathways

“…There is evidence that some of the seaweed detritus material ends up in the deep ocean, it has been observed in the deep sea below 1000 m (Krause‐Jensen & Duarte, 2016). Taking sediment core samples in the deep sea, gives insight on the amount of seaweed derived carbon and existence in the deep sea (Hidayah et al, 2022; Rose & Hemery, 2023; Santos et al, 2019), but these samples do not indicate where the carbon originated and what the ratio of sequestration per biomass would be. Ortega et al (2019) conclude that macroalgae transport to the deep sea takes, place, based on eDNA analysis.…”

Preface: Blue carbon studies in Asia‐Pacific regions: Current status, gaps, and future perspectives

“…Ecosystem connectivity can influence blue carbon dynamics because these BCEs can receive OC from upland forest as well as exchange OC among themselves (MacKenzie et al, 2021; Sasmito et al, 2020). The second paper in this special feature by Hidayah et al (2022) found that macroalgal and mangrove‐derived OC are important contributors to seagrass OC sequestration and OC stocks (Hidayah et al, 2022). Understanding the influence of coastal environmental settings on as well as the quantification of allochthonous supplies of organic matter, mineral sediment, and nutrients is an important gap in the storage and sediment OC sequestration potential.…”

Mangroves in a transforming world : Biogeochemical interactions, global change drivers, and innovative mitigation strategies

“…Mangrove, seagrass, coral (Adame et al, 2012;Briand et al, 2015;Hernández et al, 2022;León-Pérez et al, 2023;Middelburg et al, 1996;Signa et al, 2017) Mangrove, seagrass (Asplund et al, 2021;Dahl et al, 2022;Hidayah et al, 2022;Kammann et al, 2022;A. K. Mishra et al, 2023;Sullivan et al, 2021;Walton et al, 2014) Mangrove, coral (Keyes et al, 2019) Mangrove (Agraz-Hernández et al, 2018;Analuddin et al, 2021;Feller et al, 2015;Gillis et al, 2016;Moroyoqui-Rojo et al, 2015;Vaiphasa et al, 2007;Williams et al, 2013) Seagrass (Apostolaki et al, 2012;…”

“…From the sea side, organic carbon and nutrients can also be imported by seaweed (Hidayah et al, 2022), or in the form of sargassum brown tides resulting from largescale anthropogenic enrichment of continental rivers and offshore areas (Djakouré et al, 2017). This phenomenon, which began in 2011 and has occurred yearly since then, involves the influx of sargassum algae (Oyesiku et al, 2014;Sissini et al, 2019;Van Tussenbroek et al, 2017).…”