POLLEN IN THE LOWER MISSISSIPPI RIVER

In this paper we report on a 7-month study (February to August, 1987) of pollen transported by the Mississippi River. Results are presented for samples collected at Pointe a la Hache, Louisiana. Pollen concentrations range from 657 grains 1-1 in August to 8479 grains 1-1 in April and are positively correlated to suspended sediment concentrations (r = 0.81). Using this relationship it is calculated that c. 1 × 1019 grains of pollen and spores are discharged annually into the Gulf of Mexico, a significant source of pollen to marine sediments there. The pollen assemblage appears to reflect pollen transported from sources throughout the Mississippi River drainage system, but some exclusively northern taxa are present at very low concentrations. The relative abundance of most components varies temporally in relation to factors of pollen production, runoff in the drainage area and characteristics of river flow. High concentrations of indeterminable grains, corresponding to river flood stages, are assumed to be due to resuspension of river deposits and may be used as an indicator of fluvial transport. © 1990.