Pollen Deposition on and under the Water Surface

In the summers of 1974 and 1975 pollen deposition was studied in two bays of the Baltic Sea near Stockholm with roofed and unroofed samplers mounted on rafts and with samplers submerged to levels of 30 and 60 cm over the bottom. The unroofed traps show larger totals of pollen grains than the roofed samplers. Sufficient data could not be obtained to establish that the totals of pollen grains in the submerged samplers at level 30 cm were larger than the totals at level 60 cm. The differences in pollen rain in the two seasons can be attributed mainly to the meteorological conditions, viz, to the particularly dry and warm summer of 1975. In the raft samplers the percentages of redeposited arboreal pollen are lower than in the submerged ones. Transport by currents and redeposition influence the pollen spectra in the submerged samplers. The pollen spectra in samplers over and under the water surface depend mainly on the specific composition of the surrounding vegetation. Pollen transport over short distances is therefore of great importance. No evidence was found of long-distance pollen transport.