Science Serving Maryland's Coasts
Patricia Glibert, Ph.D.
Horn Point Laboratory
The Release of Nitrogen by Diatoms and Flagellates: Following a Pulse of Nitrate
This experiment studied the mechanism by which diatoms reduce NO3- to NO2- and NH4+ to dissipate electron energy acquired from the sunlight due to turbulent mixing. This mechanism allows the diatoms to not only survive conditions of high nitrate concentration and excessive irradiance, but to actually thrive and benefit from it. To demonstrate that this mechanism occurs, three diatoms and three flagellates were placed in an irradiance which allowed phytoplankton to grow at a normal rate as well as conditions of irradiance ten times that of the normal growth rate. This was repeated at temperatures of 20°C, 15°C, and 10°C. Concentrations of NO3-, NO2-, and NH4+ were measured over a span of three hours for cultures at normal irradiance and at high irradiance. As a result, the diatoms, at all temperatures, produced more NO2- and NH4+ at high irradiance. This remained relatively true for all species. The flagellates, while they may have produced NO2- and NH4+, did so at the same rate as the normal irradiance cultures or at a rate even less than the normal light treatment. This remained relatively true for all species at all temperatures. This evidence suggests that diatoms have an additional mechanism to dissipate electron energy that flagellates do not appear to have.
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