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

Watanabe, Kenta, Seike, Koji, Kajihara, Rumiko, Montani, Shigeru, Kuwae, Tomohiro
Global change biology 2019 v.25 no.3 pp. 1063-1077
climate change, habitats, models, organic carbon, sea level, subsidence
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.