Molecular and physiological responses of two classes of marine chromophytic phytoplankton (diatoms and prymnesiophytes) during the development of nutrient-stimulated blooms

Generic taxon-specific DNA probes that target an internal region of the gen e (rbcL) encoding the large subunit of ribulose-1,5-bisphosphate carboxylas e/oxgenase (RubisCO) were developed for two groups of marine phytoplankton (diatoms and prymnesiophytes), The specificity and utility of the probes we re evaluated in the laboratory and also during a 1-month mesocosm experimen t in which we investigated the temporal variability in RubisCO gene express ion and primary production in response to inorganic nutrient enrichment. We found that the onset of successive bloom events dominated by each of the t wo classes of chromophyte algae was associated with marked taxon-specific i ncreases in rbcL transcription rates. These observations suggest that measu rements of RubisCO gene expression can provide an early indicator of the de velopment of phytoplankton blooms and may also be useful in predicting whic h taxa are likely to dominate a bloom.