Regional-scale distributions of pollen and spore assemblages in alluvium around the Bohai Sea: An essential step toward understanding marine palynological sources in China

Abstract

To better understand the provenance and transport paths of modern pollen and spores in the Bohai Sea, we analyzed 104 surface alluvial samples from its sixteen inflowing rivers and 56 modern surface pollen samples from around Bohai Sea in the East Asia Surface Pollen Database. Our results revealed that the pollen assemblages of the inflowing rivers were dominated by non-arboreal pollen types, which accounted for an average of 60% of the pollen and were represented primarily by Chenopodiaceae; the percentages of arboreal pollen reached an average of 23%; fern spores accounted for the lowest percentage of the spores and pollen. The characteristics of the pollen assemblages in the alluvium of the inflowing rivers, especially large rivers, reflected the vegetation of upstream sampling points rather than the characteristics of the vegetation around the sampling points. The vegetation types represented by the pollen and spores in the short-source rivers or seasonal rivers were beyond the range of the drainage basin, especially the trees and ferns, and differences of the watershed vegetation of the inflowing rivers led to different pollen assemblages in the alluvium in the study area. The Yellow River is the main source of modern surface pollen in the Bohai Sea. Unlike the pollen of the inflowing rivers, the pollen assemblages in the Bohai Sea were dominated by arboreal pollen, especially Pinus. The fern spores were dominated by Selaginella, but non-arboreal pollen accounted for relatively low percentages of the pollen.