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

• Published in: Holocene (Sevenoaks) 2007-12, Vol.17 (8), p.1129-1139
• Main Authors: Wooller, Matthew J., Morgan, Rebecca, Fowell, Sarah, Behling, Hermann, Fogel, Marilyn
• Format: Article
• Language: English
• Subjects: Avicennia germinans; Carbon; Forests; Geological time; Isotopes; Marine; Nitrogen; Oxygen; Paleoecology; Pollen; Rhizophora mangle
• ISSN: 0959-6836; 1477-0911
• DOI: 10.1177/0959683607082553

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.