The Development of a Natural Plankton Population in an Outdoor Tank with Nutrient-Poor Sea Water. II. Changes in Dissolved Carbohydrates and Amino Acids

Abstract

Interrelations between plankton communities and dissolved carbohydrates and amino acids were investigated under near-natural conditions in sea water enclosed in plastic tanks. In summer 1972 the development of a natural plankton population was followed in a 3-m3 plastic tank for 28 d. In the course of this experiment, concentrations of dissolved neutral carbohydrates and free amino acids were determined. Results are in the range of published data for the open sea with respect to concentrations (0.2-2.5 mmoles dm-3 total sugar; 0.2-3.1Ilfnnles dm-3 total amino acids) and qualitative composition. A plankton succession was observed during the experiment; this was accompanied by distinct alterations in the concentrations of dissolved amino acids and carbohydrates. Glucose and lysine occurred in highest concentrations. Maximum rate of increase was 29 mmoles dm-3 h-1 for glucose. and 25 mmoles dm-3 h-1 for lysine. The rates of decrease are in the same range as bacterial uptakeratesdetermined by various authors employing tracer methods. Numerous positive, highly significant correlations suggest heteropoly saccharides as one source of individual carbohydrates. Relations between certain species within the plankton succession and occurrence of dissolved organic substances were observed. Significant positive correlations existed between glucose and diatoms as well as between glucose, galactose. mannose, arabinose and ribose a.,d phytoplankton biomass. There were also several significant positive correlations of amino acids, especially of valine. leucine and isoleucine with other biological parameters.