Dinoflagellate contributions to the deep sea
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For the first time, sediment trap samples from several depths in the deep sea were analyzed to estimate both the types and amounts of mineral contributed by dinoflagellates to the deep sea sediment flux. Thecal remains of dinoflagellate motile stages were almost entirely restricted to the upper few hundred meters of the water column, supporting the generally accepted explanation of their absence in the fossil record (i.e., theca are composed of cellulosic material which is destroyed before they may be incorporated into bottom sediments). The main contribution to the sediment flux is composed of resting cysts routinely produced in the life cycles of just a few of the more obscure oceanic dinoflagellates, probably species of Scrippsiella or Ensiculifera. The cyst assemblage sedimenting out from plankton at present is overwhelmingly dominated by a few small calcareous types (up to several thousands/m2/day). If not dissolved, these may accumulate in paleontologically significant amounts in bottom sediments to give the most representative fossil record of oceanic dinoflagellates. "Oceanic assemblages" of organic-walled cysts from Recent deep-sea sediments previously described by palynologists probably represent long distance transport from more coastal regions rather than oceanic dinoflagellate production.