ISSN:
1573-5117
Keywords:
the diatom Fragilaria crotonensis
;
bacteria
;
dissolved organic carbon
;
physiological state
;
molecular weight composition
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Responses of bacteria to dissolved organic carbon (DOC) released from healthy and senescent Fragilaria crotonensis (Bacillariophyceae) were examined in experimental systems. The alga released DOC actively, although the concentration fluctuated greatly in both the axenic (the alga alone) and the mixed (the alga plus the enriched bacteria) cultures. In the control (the bacteria alone) cultures, both DOC concentration and bacterial density were low and almost constant throughout the experiment: 5.0 mg C 1−1 and 1.1 × 105 cells ml−1, respectively. In the mixed cultures, bacterial growth was negligible during the exponential growth phase of the alga, but rapid proliferation of the bacteria occurred after the onset of the stationary growth phase. As the bacterial population grew, the density of senescent algal cells also increased. When the bacteria were fed on the DOC from healthy algae, their growth rate was relatively low (0.44 d−1), but the maximum cell density was high (6.4 × 105 cells ml−1). Conversely, when the bacteria fed on the DOC of senescent algae, they grew at a relatively high rate (0.51 d−1), but the maximum cell density was low (2.8 × 105 cells ml−1). These results suggest that DOCs released from dominant phytoplankton species in different physiological states affect the biomass and activity of bacteria.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00008912
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