Applications of Pollen Analysis in Estuarine Systems

Pollen and spores have an outer covering that is resistant to decay in anaerobic estuarine sediment, and their morphological and textural features, such as shape, size, aperture type and ornamentation, enable microscopic identification. Pollen analysis compares assemblages of pollen and spores in stratigraphic cores relative to the modern environment to reconstruct vegetation assemblages of past environments. Stratigraphic cores from estuarine deposits provide time-depth sequences of sediment samples, and the laboratory procedure in pollen analysis involves concentration of the pollen and spores. Microscopic examination allows identification, although it is difficult or impossible to distinguish between some genera and species, and down-core assemblages can be interpreted by comparison with those found in surface sediment samples and local and regional community structures of vegetation. Both relative abundance, and absolute concentration, are used to interpret the palaeo environment. Records have shown vegetation changes to be controlled by relative sea level change, and estuarine evolution such as progradation, infill, shoreline retreat, and by human influences. Estuarine sediments with high mixing and inorganic sediment content generally yield poorer pollen analysis records relative to estuarine sediments with an undisturbed time/depth sequence of stratigraphy and with limited reworking. Lower energy zones in central areas of wave and tide dominated estuaries have proven to be most useful for palaeo-environmental reconstruction by pollen analysis.