Predictive Value of Adenylate Energy Charge for Metabolic and Growth States of Planktonic Communities in Lakes

Abstract

The adenylate energy charge (EC), defined as (ATP + 4ADP)/(ATP + ADP + AMP), was measured during the development and crash of a phytoplankton bloom, from Nand P-limited cultures of lake algae as well as from phytoplankton stressed from additions of toxic pollutants. Except for a small increase in EC in the early phase of the bloom there were no changes in EC that could be interpreted in terms of community energy status. EC values remained within 0.6-0.7, a dynamic range too narrow to permit its usefulness as a basis for defining the growth or energetic status of the community. Pure cultures of lake algae showed decreased EC during phosphorus limitation but not during nitrogen limitation. During natural successional events a mixture of low EC and high EC cells leads to a holding of the community within narrow limits. Catastrophic events, such as addition of toxic pollutants, may provide sufficiently large departures from the natural levels of EC so it has predictive value in terms of metabolic stress.