A multi-proxy approach to determine paleoecological change of mangroves, during the holocene, in Belize, Central America

Abstract

This thesis presents multiple analyses of mangrove peat cores from Spanish Lookout Cay (BT - 79) and from along the banks of the Sibun River (SR-63), Belize to examine ecosystem responses to environmental change during the Holocene. Radiocarbon measurements showed these sites were colonized by mangroves ~8,000 cal. yrs BP and have decreased sedimentation rates from ~6,000 to ~1,000 cal. yrs BP, which is attributed to a decrease in sea-level inundation. Core SR-63 has a change in lithology from primarily mangrove peat to fluvial material at 2,500 cal. yrs BP, which is attributed to erosion inputs of the drainage basin. Changes in the pollen assemblage, such greater input from non-mangrove pollen, are coeval with changes in sedimentation rates at both sites. Subfossil mangrove leaves, from core BT-79, are used for stable isotope ([delta]¹⁵N, [delta]¹³C, and [delta]¹⁸O) analyses to illustrate past physiology and seawater inundation. The composition of organic material in core SR-63 changes from autochthonous to allochthonous sources, which is coeval with the change in lithology. A decrease in the rate of sea-level rise is assumed to be the cause of the significant changes seen in these mangroves, which counters existing sea-level curves.