Effects of different separation and concentration methods on counting and germination of cysts of Scrippsiella trochoidea

Dinoflagellate cyst is one of the most important fossil components in marine sediments. A range of laboratory preparation methods have been developed to deal with the extraction of dinoflagellate cysts in sediments. Here, we present a comparison of sieving and sodium polytungstate (SPT) density-gradient centrifugation on counting and germination of cysts of Scrippsiella trochoidea. The recovery rate of pure cysts was 74.5% after sieving through 125 μm and 20 μm screens successively. The recovery rate decreased to 61.9% for cysts in sediments after sieve procedures. The recovery rate was 68.6% for pure cysts after 1.5 g/cm³ SPT gradient centrifugation, and decreased to 42.6% for cysts in sediments after sieving and SPT gradient centrifugation successively. Sieving did not influence cyst germination, however the germination rates decreased significantly after SPT centrifugation. Meanwhile, SPT treatment made morphological changes of cysts of S. trochoidea. The results suggest that sieving is a reliable method for separation and concentration of cysts from sediments.