A palynological and stratigraphic analysis of mangrove sediments at Punta Galeta, Panama

Paleoecological records recovered from mangrove peat, were used to reconstruct the timing and pattern of mangrove development in a Caribbean mangrove forest and, in doing so, provide a historical context for modern ecological studies as well as conservation efforts. Paleoecological records afforded the means and motivation for two additional studies, which included a correlation analysis of mangrove tree distribution and pollen deposition and an analysis of the role of mangrove peat deposits in global soil carbon inventories.;Three sediment cores were recovered from Punta Galeta, Panama and core stratigraphy, sediment characteristics and palynomorph records were analyzed in conjunction with local and regional pollen, coral reef, and sea level records to reconstruct patterns of mangrove development. Three transects were established within the mangrove forest, along which vegetation was surveyed and surface samples were collected for pollen analysis. Soil organic matter and organic carbon were measured at throughout the sediment cores by loss on ignition and elemental analysis.;Results from the paleoecological study indicate that mangrove forest was preceded by a freshwater wetland that existed from 6000 to 2000 yr B.P. Seawater incursion, between 1900 and 1450 yr B.P., led to salinization of the freshwater wetland environment and colonization by mangrove forest. Mangrove development was largely successional and can be reconciled with transgressive sea level rise on the basis of marine incursion, preferential colonization by Rhizophora, and increased rates of mangrove peat accumulation. The analysis of mangrove tree density and pollen concentrations resulted in a significant, but not directly proportional, correlation. R. mangle pollen is overrepresented, relative to the proportion of R. mangle trees, by 21% and both L. racemosa and A. germinans pollen are under-represented, relative to L. racemosa and A. germinans trees, by 11%. This disproportionate relationship is due to differences in pollen dispersal techniques as well as local meteorological conditions. Results from sediment analysis reveal that the relationship between soil organic carbon (OC) and organic matter (OC) in mangrove peat is defined by the function OC = 0.4187(OM) - 1.8814. At Punta Galeta, measurements of soil carbon storage were comparable to global stocks and carbon accumulation represented long-term rates due to peat sedimentation rates.