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Christine Höll, Helmut Willems:
Calcareous dinoflagellates and temperature: Sphaerodinella albatrosiana, S. tuberosa, Orthopithonella granifera in laboratory experiments
(Poster)

For the possible use of calcareous dinoflagellates in palaeoecological analyses, it is important to determine the relationship between cyst production and abiotic factors such as temperature. The effect of different temperatures on culture growth and cyst production was tested on different marine calcareous dinoflagellates in laboratory experiments. The species Sphaerodinella albatrosiana, Sphaerodinella tuberosa and Orthopithonella granifera have been chosen for the investigation, since they often dominate the calcareous dinoflagellate cyst association in oceanic regions during modern and Late Quaternary times. The isolates of the used strains were collected in the Atlantic Ocean. A temperature gradient box (TGB), which allows the simultaneous testing of a wide range of temperatures on phytoplankton, was used for the experiments. Different strains of S. albatrosiana, S. tuberosa and O. granifera were cultured in the TGB at temperatures ranging from 6°C to 33°C. When possible, each culture was present twice in the TGB; on one row, measurements were carried out (mixed cultures), the other row stayed resting (unmixed) for the duration of the experiment.

All investigated species grew in a similar temperature range, although differences were obvious between the single species. When counting the cysts, different calcification degrees were distinguished. Special attention was given to the well-calcified cysts, as they are assumed to be fossilisable.

The examined species form well-calcified cysts mainly in the temperature range from 14°C to 30°C, with clear differences between each species. Especially striking is that the formation of well-calcified cysts in all three species is two times higher in the unmixed cultures compared to the mixed ones.

The results of the laboratory experiments suggest the presence of the fossilisable well-calcified cysts of the investigated species in warm regions of the oceans, possibly in greater amounts where the upper water-column is less turbulent.

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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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