| Abstract: | Two marine diatoms were studied singly and in mixed culture. Thalassiosira pseudonana (Hust.) Hade & Heimdal was capable of a higher growth rate (μmax) than Phaeodactylum tricornutum Bohlin. In two-species batch cultures P. tricornutum took over in the latter portion of the exponential phase, possibly due to allelopathy. The filtrate from this species caused an initial lag phase and a reduced terminal population density for T. pseudonana. Two-species continuous cultures showed verification of these interactions. At high dilution rate (i.e., high growth rate) P. tricornutum washed out when added at low density, whereas T. pseudonana maintained constant cell density. However, when sufficient density of P. tricornutum was added as a contaminant, both species washed out. At a lower dilution rate P. tricornutum increased in density when added and eventually reached a stable population; T. pseudonana then washed out. |
