PRESERVATION OF ORGANIC-WALLED DINOFLAGELLATE CYSTS IN DIFFERENT OXYGEN REGIMES - A 10,000 YEAR NATURAL EXPERIMENT

The occurrence of organic-walled dinoflagellate cysts in (fossil) sedi ments depends on several factors, including as the ecological preferen ces of the cyst-forming dinoflagellates, cyst production, transport an d preservation. Although laboratory experiments have shown that severa l cyst species are sensitive to chemical treatment, no information abo ut the selective preservation of dinoflagellate cyst species in natura l environments has previously been presented. Here, we present data on the effects of oxygen availability in bottom sediments on a cyst asse mblage from the ungraded Madeira Abyssal Plain f-turbidite of which on ly the upper layer has been oxidized. Based on differences in species composition between the oxidized and underlying, unoxidized layers of this turbidite, the influence of oxygen availability on the preservati on of individual species has been estimated. Cyst species have been cl assified in ascending order of resistance to oxygen availability in se diments as: (1) highly sensitive (cysts formed by Protoperidinium spec ies), (2) moderately sensitive (e.g. Spiniferites species), (3) modera tely resistant (e.g. Impagidinium paradoxum and Nematosphaeropsis laby rinthus) and (4) resistant (e.g. Impagidinium aculeatum).