Mid to late Holocene sea-level rise and precipitation variability recorded in the fringe mangroves of the Caribbean coast of Panama

Abstract

Throughout the Holocene, two of the most important factors involved in the evolution of tropical coastlines have been fluctuations in sea level and regional climates. The geological record provides insightful realizations of the complex interaction between these two factors, improving our understanding of the evolution of littoral zones. Here we present the sedimentary record of a mangrove swamp located in Punta Galeta, Caribbean coast of Panama. Through the conjunction of geochemical and biological sedimentary indicators, we reconstruct environmental dynamics of the area for the last ~5200 years. Between ~5200 and ~1800 cal yr B.P., the progressive dominance of carbonates and a decrease of mangrove pollen indicate increasing marine influence in the area, probably facilitated by a progressively drier climate. Between 3100 and 1800 cal yr B.P., the embayment was flooded by marine water resulting in a landward migration of mangroves. From ~1800 cal yr B.P. to present, the pollen and organic matter records indicate that mangrove vegetation belt recovered, contributing a large proportion of organic matter to the sediment and advancing the shoreline seaward. The maturation of the mangrove forest has resulted in a progradation process that offsets between 4 and 5 m of sea level rise occurred through the last ~5000 years. This process was facilitated by the progressive decrease in rates of sea level rise and by increasing sedimentation rates resulting from a higher accumulation of organic matter from the more vigorous vegetation and more terrigenic input associated with higher regional precipitation. The record of Punta Galeta demonstrates that the evolution of fringe mangroves throughout the Holocene has been mostly driven by sea level rise, which effects are potentially offset by erosion during times of high precipitation. Thus, across the Caribbean coast, precipitation regimes have played a pivotal role at defining the structure and function of mangrove communities. • Sea level rise has dominated coastal dynamics in Punta Galeta through the Holocene. • Mangroves have played a central role at counteracting sea level rise. • Precipitation variability has modulated the effect of sea level rise on the regional coastline.