Assessing pollen distribution patterns and provenance based on palynological investigation on surface sediments from Laizhou Bay, China: an aid to palaeoecological interpretation

Assessing pollen distribution patterns in the sea is essential to understanding pollen provenance, upon which subsequent interpretation of Quaternary pollen data from marine sediments in the same study area should be soundly based. Here we present palynological data from seafloor sediments in Laizhou Bay and analogous samples from its inflowing rivers to elucidate the distribution patterns and provenance of modern palynomorphs. Our results demonstrate that the pollen assemblages of marine areas are dominated by arboreal pollen types, especially Pinus, and herbaceous pollen types are dominated by Chenopodiaceae and Artemisia. The higher pollen concentrations occur in the southwest area of Laizhou Bay, and the lower pollen concentrations are mainly distributed in the nearshore area of the Yellow River estuary. Such pollen distribution patterns are tightly correlated with the distribution features of grain size of the surface sediments. Specifically, the sediments with higher pollen concentrations are of very fine and fine silts, whereas those with lower pollen concentrations are of fine sands. The results of PCA analysis suggest that pollen grains in the nearshore areas are mainly transported by water flows, of which herbaceous pollen show relatively higher concentrations; while pollen grains in the offshore areas are largely carried by winds, especially those pollen types with sacs, such as Pinus. Dissimilarity analysis between marine and alluvial samples indicates that the pollen spectrum show close linkage with the regional vegetation in the surrounding watersheds. Pollen quantitative characteristics and pollen assemblage changes in different parts of the marine areas indicate various pollen provenance and changing landscape of terrestrial vegetation, particularly along the inflowing rivers. Our Assessments on pollen distribution patterns and provenance based on palynological investigation would strongly aid Quaternary palaeoecological and palaeoclimatological interpretation for our study area.