FREE AMINO-ACIDS AS A BIOCHEMICAL INDICATOR OF STRESS IN THE ESTUARINE BIVALVE MACOMA-BALTHICA

The use of free amino acids (FAA) as a stress indicator was assessed d uring a copper exposure experiment for specimens of the estuarine biva lve M. balthica from a geographical gradient extending from the Nether lands to its most southern limit of distribution in the Gironde, Franc e. Changes in FAA were significant. A higher alanine content at the st art of the experiment coincided with a lower mortality-rate during cop per exposure. During copper exposure the tissue concentrations of alan ine increased. It is concluded that especially the concentrations of a lanine, and to a lesser degree the taurine/glycine (T/G) ratio, can be used as stress-indicators for M. balthica. Animals near the southern limit of their distribution showed the strongest deviations from avera ge values. The age of the animals (2-7 years) had no influence on resu lts.