Enrichment experiments for determining nutrient limitation: Four methods compared1

Abstract

Four nutrient bioassay techniques were compared in studies of an oligotrophic, soft‐water lake in New Hampshire. Enrichments of large polyethylene enclosures, continuous cultures of the natural phytoplankton community, and long term 14 C bioassays agree in demonstrating that nitrogen and phosphorus limit phytoplankton growth in this lake. However, in short term (4–30 h) 14 C bioassays, nitrogen and phosphorus enrichments did not stimulate phytoplankton production. Care should be exercised in extrapolating results from short term, bottle bioassays to measures for controlling eutrophication.