NUTRIENT CONCENTRATION IN TISSUE OF THE MACROALGA ENTEROMORPHA AS A FUNCTION OF NUTRIENT HISTORY - AN EXPERIMENTAL EVALUATION USING FIELD MICROCOSMS

Nutrient enrichment experiments were conducted to assess the relationship between nutrient concentration in the tissue of the macroalga Enteromorpha sp. and nutrient history. Experimental units were outdoor microcosms containing mixed assemblages of algae representative of communities commonly found in coastal lagoons of southern California, USA. We determined the relationship between nutrient supply rates (nitrogen and phosphorus as well as N:P ratio), water-column nutrient concentrations, and macroalgal tissue nutrient concentration in samples taken from experimental microcosms containing macroalgae, phytoplankton, and cyanobacterial mats, and treated with 13 combinations of nitrogen and phosphorus addition. The regression coefficients that described the fit of the relationships between tissue P and both P supply rate and water-column concentration were greater than for the same relationships f or N. The relationship between tissue nutrients and either measure of nutrient history (water-column concentration or supply rate) was most useful when the nutrient was not limiting.