Diatoms in Surface Sediments: A Reflection of Coastal Upwelling
Recent sediments influenced by overlying strong coastal upwelling off Peru, off South West Africa, and within the central Gulf of California can be differentiated from sediments of adjacent oceanic regimes by diatom floral analysis. Abundant remains of well-preserved diatoms are deposited in each area beneath zones of recurrent high primary productivity. The distribution patterns of Chaetoceros spores and valves of other meroplanktic diatom species preserve in the sediments off Peru the sinuous seaward boundary of upwelled coastal waters and may reflect the evolution of the biota influenced by episodic nutrient enrichment. Off South West Africa the initial response to nutrient enrichment is preserved in several nearshore areas by a high abundance in the sediments of valves of Delphineis karstenii. An association of large centric diatoms occurs in samples from these areas, and Chaetoceros spores, representing a final stage of species succession, occurs in highest abundance on the outskirts of the sediment patches. Laminated sediments of the Gulf of California provide deposits representing single upwelling seasons. Core material available from this area will allow fine resolution documentation of the influence of coastal upwelling on relic diatom abundance, preservation, and species composition. Keywords: Chaetoceros, Costal upwelling reflection, Delphineis, Diatoms, Sediments, Surface sediments, Water off, Winf off.