Responses of Algae and Bacteria to Nutrient Additions in Bottled Lake Water

Surface water of Lake Yunoko, a small eutrophic lake in central Japan, was bottled, enriched with glucose and/or mineral nutrients, and incubated for five days in the surface layer of that lake. Bacteria reacted promptly to the addition of glucose. When, however, an ample amount of glucose was added to the lake water, certain mineral nutrients, possibly nitrogen, became secondarily limiting to the growth of bacteria. Although mineral nutrients alone stimulated the growth of algae, the stimulatory effect was far greater when both glucose and mineral nutrients were enriched.