DIATOMS IN SURFACE SEDIMENTS OF THE INDONESIAN ARCHIPELAGO AND THEIR RELATION TO HYDROGRAPHY

Diatoms from 53 surface sediments (water depth 350-7200 m) of the Indo nesian Archipelago were studied to determine the recent distribution o f important assemblages. Three significant assemblages were distinguis hed, each related to hydrographic parameter(s) of the overlying water mass. The first assemblage is related to the warm saline surface water s of Pacific and Indian Ocean origin; the second assemblage reflects t he low-salinity lobe in Makassar Strait; and the third corresponds to major seasonal upwelling areas in the Arafura Sea and south of Java. T he normalized ratio of typically Pacific Ocean and Indian Ocean specie s reflects the fluctuations of the Pacific versus Indian Ocean inflow during the Late Quaternary. Absolute diatom abundances (ADA; in valves g(-1) carbonate-free dry wt) and diatom accumulation rates (DAR; in v alves cm(-2) ka(-1)) of autochthonous species did not correspond to da ily rates of primary production in the photic zone and consequently ca nnot be used for paleoproductivity estimates. Besides vertical transpo rt some lateral transport of diatoms occurs, as was demonstrated by th e presence of three groups of allochthonous species. They are indicato rs of productivity in the littoral environment, bottom currents and ri ver outflow.