Observations on diurnal vertical migration and phased cell division for three coexisting marine dinoflagellates

• An experiment was performed in the beginning of September 1988 in the Gullmar Fjord, eastern Skagerrak, in order to study diurnal vertical migration and phased cell division for a natural phytoplankton community dominated by the dinoflagellates Prorocentrum minimum, Prorocentrum micans and Cerattum furca. A 1 80 m high and 0.30 wide non-transparent PVC cylinder was filled with surface water containing the dominant dinoflagellates. An artificial halocline was created by adding high salinity, nutrient-rich bottom water to the bottom of the cylinder Cell densities were measured at seven depths at 11 times during 48 h Physical parameters (temperature, salinity, phosphate, nitrate, ammonia and silicate) were measured at the start and at the end of the experiment in the water column above and below the halocline. Strong diurnal vertical migration patterns were found for all three species with an aggregation of cells at the surface in the morning and during the day and at the bottom at night. The descent and ascent seemed to start before sunset and sunrise respectively and all species were able to migrate through the strong artificial halocline. Some differences were found in the speed and timing of migration between the species with P.minimum having the most pronounced and fastest migration of the three Cell division frequency was highest at 05.00 at the bottom and also at the surface At other times and depths the division was always close to zero. The decrease in especially nitrate concentrations in the bottom water of the cylinder suggests that these dinoflagellates are capable of dark nitrogen assimilation. 

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Terrestrial, freshwater and marine ecology

Terrestrisk, limnisk och marin ekologi

Aquatic Ecology

Akvatisk ekologi

Publikations- och innehållstyp

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