RATES OF AMINO-ACID-UPTAKE AND MINERALIZATION IN RESURRECTION BAY (ALASKA) SEDIMENTS

The rates of uptake and mineralization of glutamic acid, alanine, lysine, serine and glycine were measured in sediments from Resurrection Bay, Alaska, USA, using C-14-labeled amino acids. Amino acid concentrations and specific activities were determined by high performance liquid chromatography. The fate of radiolabeled amino acids added to killed control sediments was also investigated. Free amino acids were lost from the dissolved pool by both bacterial uptake and adsorption to sediment particles. Adsorption was the dominant process for the basic amino acid lysine and was responsible for about half of the glutamic acid and alanine removal from solution. Rates of bacterial mineralization of porewater amino acids, calculated using a model which corrects for the effects of adsorption, were 8 (glutamic acid), 1 (alanine), 0.7 (lysine), 1 (serine) and 3 (glycine) nmol cm-3 sediment d-1. These rates indicate that amino acids could be quantitatively important intermediates in the mineralization of organic nitrogen in this sediment.