Common Era sea-level changes reconstructed from a mangrove in Southeast Africa

This is the first Common Era mangrove-based relative sea-level (RSL) reconstruction from the east coast of South Africa, a far-field location useful for increasing the global spread of Common Era RSL data. The Mngazana estuary is a permanently open small estuary with the largest Rhizophora mucronata stand in South Africa. Intertidal vegetation at Mngazana is zoned vertically by elevation, with mangrove present between just above Mean Sea Level (MSL) and just below Mean High Water of Spring tides (MHWS). We use the vertical range of modern mangrove vegetation and diatom assemblage analysis to produce RSL estimates. We also developed classical and Bayesian transfer function models but poor fossil diatom preservation prevents us using these models to reconstruct late Holocene RSL. We reconstruct RSL ~0.7 m below present around 1050 CE, rising to present over the last millennium. In contrast to the RSL data from Mngazana, glacial isostatic adjustment (GIA) modelling indicates slightly falling RSL in the last ~1500 years. The lack of evidence for falling RSL in the last millennium at Mngazana suggests that the processes dominating the RSL budget in this region are not currently captured by GIA modelling.