Distribution and provenance of modern pollen and spores in the surface sediments of Liaodong Bay, China

To elucidate modern pollen and spore distribution and provenance based on their dispersal patterns, we analyzed 72 surface sediment samples from Liaodong Bay, China and 39 analogous samples from its five inflowing rivers. Our results reveal that most of the pollen and spores in the nearshore marine sediments (water depth < 8 m) originated from riverine input and that their assemblages corresponded well to the watershed vegetation. Variation in the pollen assemblages in different parts of the marine area could reflect differences in local vegetation. The content of herbaceous pollen decreased with increasing distance offshore, while arboreal pollen and spores increased. Due to the differences in the sedimentary environments and the source areas of pollen and spores, pollen concentrations in the marine area were higher than those in analog sediments in the modern alluvium of the inflowing rivers. The highest pollen concentrations occurred in the northwestern area of Liaodong Bay, where pollen was derived from multiple inflowing rivers. According to the distribution characteristics of pollen and spores from alluvium to marine sediments, it can be inferred that most pollen grains such as Artemisia, Chenopodiaceae, Gramineae, Cyperaceae, Typha, deciduous Quercus, Betula, and Corylus pollen were primarily transported through the inflowing rivers, whereas Pinus and Carpinus pollen were likely to have been transported by wind. The results of DCA [detrended correspondence analysis] analysis and analog dissimilarity analysis suggested that the pollen-spore distribution in the nearshore area of Liaodong Bay mainly reflects fluvial and marine hydrodynamics or water sorting effects, as well as the vegetation distribution onshore. These findings are of critical importance to the interpretation of Quaternary marine pollen data from Liaodong Bay, China.