SOURCES OF NITROGEN AND PHOSPHORUS SUPPORTING THE GROWTH OF BACTERIOPLANKTON AND PHYTOPLANKTON IN AN OLIGOTROPHIC CANADIAN SHIELD LAKE

We used a dilution gradient technique to determine the relative import ance of N and P derived from the dissolved pool, storage, and recyclin g by planktonic consumers to the growth of bacteria and algae in an ol igotrophic lake. Recycling was the dominant source of N for both algae and bacteria and the dominant source of P for bacteria. However, stor age was an important source of P for algae early in the year, but P re cycling was a dominant source for algae late in the year. Models of nu trient flux in the microbial and classic food webs must be combined in a manner consistent with the integrated nature of these fluxes.