Original scientific paper

Some Observations on the Vertical Migrations of the Dinoflagellate Prorocentrum micans Ehrenberg in the Lim Fjord (Northern Adriatic)

Branka Filipić ; Hrvatska

Abstract

Diurnal vertical migration of the dinoflagellate Prorocentrum micans Ehrenberg was investigated under field conditions in relation to the underwater light field, and the vertical distribution of nutrients (phosphates and nitrates). Water samples were taken in the Lim Fjord at 4-hour intervals over a 48 hr period. Samples were collected from 0, 2, 5, 7, 10 and 13-m depths for microscopical analysis of the species present, and at 0, 5, 10 and 13 m for other physical and chemical measurements.
The changes in the vertical distribution of P. micans cell densities during the investigation show a periodicity, indicating that the dinoflagellate is capable of undergoing diel vertical migrations. Results indicated that P. micans »avoids« surface layers and accumulates at 5-m depth during the daylight intensities (Figs. 2, 3, 4). During the night, with the lowering of light intensities, the algae migrated to the deeper portions of the water colum (10—13 m). It is hypothesized that this downward movement is related to the availability of phosphate, a nutrient considered limiting phytoplankton production in the Northern Adriatic. Nitrate occurred at concentrations considered non-limiting throughout the water column, and in contrast to phosphate, higher concentrations were found in the upper layers (Figs. 2 and 3).

Keywords

Hrčak ID:

159158

URI

https://hrcak.srce.hr/159158

Publication date:

31.12.1985.

Article data in other languages: croatian

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