THE PHYSIOLOGICAL ECOLOGY OF A FRESHWATER DINOFLAGELLATE BLOOM POPULATION: VERTICAL MIGRATION,NITROGEN LIMITATION,AND NUTRIENT UPTAKE KINETICS1,2 |
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Authors: | Oded S Lieberman Moshe Shilo Jaap van Rijn |
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Abstract: | The motile freshwater dinoflagellate Gymnodinium bogoriense Klebs., which forms dense blooms in Jezre'el Valley water reservoirs (Israel) appears to be physiologically suited to exploit stratified environments, where it outcompetes all other phytoplankton types. The dense summer blooms (“red tides”) were found to be nitrogen-limited. The algae's competitive advantage, however, cannot result from superior uptake capabilities: its Ks (μmol NH4·L?1) for NH4 was higher and its Vmaxμmol NH4·mg chlorophyll a?1·h?1) was lower than other phytoplankton types commonly occurring in the region. The competitive advantage of G. bogoriense probably stems from other physiological capabilities: dark ammonia and phosphorus assimilation and the ability to undertake diel vertical migration cycles between the upper photic water layers during the day and nutrient-rich deeper layers at night. These findings confirm the vertical nutrient retrieval hypothesis in migrating phytoplankton. |
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Keywords: | ammonia Gymnodinium bogoriense phosphate Pyrrophyta vertical migration |
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