Relative sea‐level change regulates organic carbon accumulation in coastal habitats

• Published in: Global change biology 2019-03, Vol.25 (3), p.1063-1077
• Main Authors: Watanabe, Kenta, Seike, Koji, Kajihara, Rumiko, Montani, Shigeru, Kuwae, Tomohiro
• Format: Article
• Language: English
• Subjects: Accumulation; Analogs; Biogeochemistry; Carbon - analysis; Carbon - metabolism; Carbon Sequestration; Climate Change; Coastal ecology; Coastal environments; coastal habitats; Conservation of Natural Resources; Ecosystem; Environmental impact; Environmental Monitoring; Environmental restoration; Estuaries; Geologic Sediments - analysis; Grasses; Habitats; Land subsidence; Modelling; Organic carbon; organic carbon accumulation; Plants - metabolism; Primary; Primary s; relative sea‐level change; Restoration; saltmarshes; Sea grasses; Sea level rise; seagrass meadows; Seawater - analysis; Sedimentary environments
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.14558

Because coastal habitats store large amounts of organic carbon (Corg), the conservation and restoration of these habitats are considered to be important measures for mitigating global climate change. Although future sea‐level rise is predicted to change the characteristics of these habitats, its impact on their rate of Corg sequestration is highly uncertain. Here we used historical depositional records to show that relative sea‐level (RSL) changes regulated Corg accumulation rates in boreal contiguous seagrass–saltmarsh habitats. Age–depth modeling and geological and biogeochemical approaches indicated that Corg accumulation rates varied as a function of changes in depositional environments and habitat relocations. In particular, Corg accumulation rates were enhanced in subtidal seagrass meadows during times of RSL rise, which were caused by postseismic land subsidence and climate change. Our findings identify historical analogs for the future impact of RSL rise driven by global climate change on rates of Corg sequestration in coastal habitats. Organic carbon (Corg) storage is one of the important functions of coastal habitats to mitigate climate change; however, the impact of future sea‐level rise on this coastal habitat function is poorly understood. Deposition records in the coastal sediments provide us historical analogs for the future impact of sea‐level rise. Our study in boreal lagoons showed that sea‐level changes altered depositional environments and habitats, affecting Corg accumulation rates. Corg accumulation rates increased in response to sea‐level rise, indicating that the Corg storage function of coastal habitats would provide a negative feedback on climate change.