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 during a copper exposure experiment for specimens of the estuarine bivalve M. balthica from a geographical gradient extending from the Netherlands to its most southern limit of distribution in the Gironde, France. Changes in FAA were significant. A higher alanine content at the start of the experiment coincided with a lower mortality-rate during copper exposure. During copper exposure the tissue concentrations of alanine increased. It is concluded that especially the concentrations of alanine, and to a lesser degree the taurine/glycine (View the MathML source) ratio, can be used as stress-indicators for M. balthica. Animals near the southern limit of their distribution showed the strongest deviations from average values. The age of the animals (2–7 years) had no influence on results.