ANOXIC OR AERIAL SURVIVAL OF BIVALVES AND OTHER EURYOXIC INVERTEBRATES AS A USEFUL RESPONSE TO ENVIRONMENTAL-STRESS - A COMPREHENSIVE REVIEW

Laboratory and field studies have demonstrated the applicability of an oxic/aerial survival as an early warning indicator of contaminant indu ced stress. The effects of xenobiotics, including heavy metals, organo metals and organics as well as contaminated field sediments have been investigated. The use of this physiological response is rapid, easily quantified and inexpensive. In most studies bivalve molluscs were inve stigated, the sea mussel Mytihus edulis L. being the favourite species . The different approaches used by various researchers, as reported in the literature, demonstrate the necessity for these experiments to be standardized. When estimating the mortality rate in a closed system o r by aerial exposure, the cause of death may not be an indication of a noxia tolerance, but may be an artifact due to the development of micr oorganisms. Therefore the use of a flow-through system is suggested in cases where the duration of a test exceeds 1 week. When the response is used for the acute assessment of water quality a closed system may be used at low temperatures in combination with an organism with a rel atively low anoxia tolerance (e.g., crustaceans). Various reasons why anoxic tolerance may be reduced by toxicants are proposed. Depletion o f fuel reserves involved in anaerobic metabolism and intoxication by f ermentative products may already commence during chronic exposure to c ontaminants, and/or the anaerobic energy metabolism may be disturbed. In general there is elevated catabolic activity during anoxic exposure , especially pyruvate derivatives are prominent end produces in muscle tissue of contaminant exposed groups.