A multiproxy peat record of Holocene mangrove palaeoecology from Twin Cays, Belize

Abstract

The extent and function of coastal mangrove ecosystems are likely to be influenced by future changes in sea level. Multiple proxies of past mangrove ecosystems preserved in a 780 cm long peat core (TCC2) taken from Twin Cays, Belize, record palaeoecological changes since ~8000 cal. yr BP. The proxies included pollen and the stable-isotope (C, N and O) compositions of mangrove leaf fragments. Rhizophora mangle (red mangrove) has been dominant at this site on Twin Cays for over ~8000 years. Variations in δ13 C and δ15N suggest past changes in stand structure between dwarf, transition and tall R. mangle through the Holocene. Marked changes in the δ18O (up to ~4‰) of mangrove leaf fragments throughout TCC2 most likely record variations in the proportion of seawater versus precipitation taken up by past mangroves, reflecting the degree of inundation of the site with seawater resulting from changes in the rate of Holocene sea-level rise. Notably, a decline in peat accumulation rate at ~7200 cal. yr BP correlates with a decrease in the rate of rise in sea level. This was not accompanied by a marked change in the pollen assemblages. However, changes in assemblage composition began to occur ~6300 cal. yr BP, with an increase in Myrsine-type and Avicennia germinans (black mangrove) pollen. An increase in the δ18O between 6100 and 5300 cal. yr BP, which correlates with other records from Central America, indicates a significant increase in the rate of rise in sea level.

Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage

“…These lateral Rhizophora roots have little secondary thickening and form a dense, spongy reticulum that covers the mudflat surface. The trees basically stand on their stilt roots but have little deep anchoring and form peat [often used for palynological studies (25,26)] on the surface of the mudflat (17).…”

Radiocarbon dating of mangrove sediments to constrain Holocene relative sea-level change on Zanzibar in the southwest Indian Ocean

“…They tolerate a salinity range that varies between fully marine water (35 ‰) in the lowest intertidal area to freshwater in upstream rivers (Smith, 1992), depending on the gradient of the flood tide and freshwater runoff (Ball et al, 1988;Hogart, 1999;Krauss et al, 2008). Their underlying sediments have the potential to provide important information on past vegetation change (Woodroffe, 1990;Blasco et al, 1996;Wooller et al, 2007) and, by inference changes in RSL (e.g. Ellison, 1989;Ellison, 2005;Horton et al, 2005;Engelhart et al, 2007;Woodroffe, 2009).…”

Mangrove development and its response to environmental change in Yingluo Bay (SW China) during the last 150years: Stable carbon isotopes and mangrove pollen

“…Pollen has proven to be the most straight-forward and effective proxy for recording changes in plant communities (Li et al, 2008;Ding et al, 2013) and is widely used for tracing historical development of mangrove forests (Versteegh et al, 2004;Ellison, 2008;Monacci et al, 2009). However, it is costly and difficult to obtain reliable and accurate pollen data, especially when pollen content is low (Versteegh et al, 2004;Wooller et al, 2007).…”