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UTILIZATION OF DISSOLVED NITROGEN BY HETEROTROPHIC BACTERIOPLANKTON: A COMPARISON OF THREE ECOSYSTEMS
Citation:
Kroer, N., N. Jorgensen, AND R. Coffin. UTILIZATION OF DISSOLVED NITROGEN BY HETEROTROPHIC BACTERIOPLANKTON: A COMPARISON OF THREE ECOSYSTEMS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/007.
Description:
The contributions of different organic and inorganic nitrogen and organic carbon sources to heterotrophic bacterioplankton in batch cultures of oceanic, estuarine, and eutrophic riverine environments were compared. he importance of the studied compounds was surprisingly similar among the three ecosystems. issolved combined amino acids (DCAA) were most significant, sustaining from I 0 to 45% of the bacterial carbon demands and from 42 to 112% of the bacterial nitrogen demands. issolved free amino acids (FAA) supplied 2 to 7% of the carbon and 6 to 24% of the nitrogen incorporated into the bacterial biomass, while dissolved DNA (D-DNA) sustained less than 5 and 12% of the carbon and nitrogen requirements, respectively. mmonium was the second most important source of nitrogen, meeting from 13 to 45% of the bacterial demand in the oceanic and estuarine cultures and up to 270% of the demand in riverine cultures. itrate was taken up in the oceanic cultures (uptake equaled up to 46% of the nitrogen demand) but was released in the two others. ssimilation of DCAA, DFAA, and D-DNA combined supplied 43% of the carbon demand of the bacteria in the oceanic cultures, while approximately 25% of the carbon requirements were met by the three substrates at the two other sites. ssimilation of nitrogen from DCAA, DFAA, D-DNA, NH, and NO, on the other hand, exceeded production of particulate organic nitrogen in one culture at 27h and in all cultures over the entire incubation period (50h). hese results suggest that the studied nutrient sources may fully support the nitrogen needs but only partially support the carbon needs of microbial communities of geographically different ecosystems. urthermore, a comparison of the initial concentrations of the different substrates indicated that relative pool sizes of the substrates seemed to influence which substrates were primarily being utilized by the bacteria.