An 1800-year record of hydrology from Great Abaco Island, The Bahamas

Abstract

Studying lake sediment cores can shed light on environmental history over the Holocene, including the influences of fire, climate, and human activities. Analyzing the compound-specific hydrogen and carbon isotope ratios of organic compounds in lake sediments allows paleolimnologists to disentangle anthropogenic and climatic influences on other proxies, such as pollen, charcoal, and bulk stable isotopes. Emerald Pond is a small pond in a solution hole on Abaco Island, The Bahamas, in an area which supports pine rockland vegetation. Previous analyses of the Emerald Pond core revealed shifts in pollen and charcoal assemblages that may reflect both the impacts of human arrival on the island ca. 1000 cal yr BP and late Holocene droughts. Here, we present new analyses of compound-specific stable hydrogen isotope ratios (δD) in terrestrially derived n-alkanes from leaf waxes preserved in the Emerald Pond sediment. We use the δD values as a proxy for past changes in watershed hydrology that reflect periods of increased and decreased moisture availability in the vicinity of Emerald Pond. Our analyses focus on the most recent 1800 years of the Emerald Pond record. Alkanes are sparse in many of the samples, but our results show variations that suggest important changes in Late Holocene paleohydrology at the site. The new hydrology record is compared to existing records of vegetation and fire at Emerald Pond, other lake sediment records from the region, with a focus on periods of drought such as the Little Ice Age (AD 1450–1850) and Terminal Classic Drought (AD 750–1100).