Pollen degradation in mangrove sediments: A short-term experiment

In order to examine pollen deterioration in mangrove sediments, surface sediment samples were collected from 4 different mangrove communities, placed in nylon gauze bags, and then buried back into their own vegetation in October 2010. At periods of 2, 4, and 6 months after burial, sediment bags were retrieved and examined. At each recovery, palynomorph percentages and concentrations were calculated as a means to investigate degradation rates of deposited palynomorphs and some physical factors affecting their preservation. It was found that although mangrove sediments are assumed to represent perfect depositional environments for the preservation of mangrove pollen due to the anoxic conditions, a high potential for loss of pollen was observed. Palynomorphs decayed more rapidly in the Ceriops tagal - Bruguiera spp. community, whereas this process seems to proceed at a slower rate in the Rhizophora apiculata - Bruguiera spp. community, possibly controlled by differences in sediment pH, salinity, grain size, and organic matter. The good pollen preservation of Rhizophora apiculata and Sonneratia alba in their own plant communites allow them to act as useful indicators of the forest communities in which they are dominant. On the other hand, quantitative compositional reliabilities of pollen from Avicennia alba, Bruguiera spp., and Ceriops tagal, tended to weaken by their progressive deterioration and poor preservation. However, a long term-experiment is still necessary to achieve a more accurate estimation of biases from such important taphonomic factors.