High-resolution palynology signals in surface sediments of coastal Hainan Island of China

Studies on pollen in marine surface sediments are important for understanding the distribution mechanisms of pollen and spores into the ocean, and they are also useful in micro-paleontological studies. In this study, high-resolution palynological analysis of marine surface sediment samples from the south and southeastern inner-shelf regions of Hainan Island was performed to understand the distribution mechanism of marine surface pollen and its relationship with terrestrial vegetation. The results indicated that fern spores are the most common type, followed by tree pollen and herbaceous pollen. A majority of total pollen and spore concentrations are dominated by fern spores because the sample sites are highly concentrated with Microlepia and Polypodiaceae spores, mainly due to anthropogenic activities. The variation in tree pollen concentrations (especially for Pinus, Quercus, and Castanopsis) suggested that these pollen grains were transported mainly by wind patterns and rivers from Hainan Island. The pollen concentrations and percentage analysis in the study area showed that the inner-shelf sites have higher values than far offshore sites, reflecting a relationship between modern pollen distribution patterns and nearby landmass vegetation. Based on the principal component analysis of the resulting pollen and spore percentages, there are two main factors affecting the pollen distribution around the study area: possible human activities that have modified Hainan Island and wind–river transport toward the study area. This is the first study to discover that the presence of fern spores across the shelf is unusual, implying widespread lateral mixing in the south and southeastern Hainan Island inner-shelf region.