Marine bacteria play an important role in food webs especially with regard to nutrient cycling. Latest investigations reveal specific populations of bacteria associated with microalgae. These bacteria live in the phycosphere and feed on algal exudates. But mechanisms controlling the community composition are still poorly understood.In this study we examined bacterial association with microalgae with focus on changes in bacterial community composition during different growth phases of the algae.We investigated 10 freshly isolated key species (diatoms and dinoflagellates) off Helgoland Roads.The morphology of the algae and two fractions of bacteria (associated and free living bacteria) were recorded over a period of eight weeks in batch cultures.The diversity and succession of bacteria was analyzed by RISA (rDNA internal spacer analysis ) and DGGE (Denaturating Gradient Gel Electrophoresis).Photosynthesis efficiency of algae was measured using PAM (pulse amplitude modulation) fluorescence.The bacterial community composition differed clearly depending upon the species of microalgae, but did not change substantially within the sampling period.It can be assumed that bacterial populations have to adapt physiologically to changing conditions in the culture.
AWI Organizations > Biosciences > Shelf Sea System Ecology
Helmholtz Research Programs > MARCOPOLI (2004-2008) > CO2-Coastal diversity - key species and food webs