Why are Early Life Stages of Aquatic Organisms more Sensitive to Toxicants than Adults?

Abstract

1.1. The selection of a suitable test species Toxicity tests are designed to determine the specific concentrations of chemicals that induce a measured effect on a target organism. However, the potency of any toxicant can be influenced by the characteristics of the chemical, as well as environmental (temperature, ph, water chemistry, salinity) and species (life stage, sensitivity, pre-exposure) specific factors. Environ‐ mental factors can either modify the toxicant itself or the immediate environment of an organism, increasing or decreasing the effects of the toxicants. Species specific factors can alter the organism/toxicant interaction by modifying the rate of uptake, distribution, elimination and detoxification pathways. Therefore when conducting toxicity tests, it is important to have controlled environmental conditions and select suitable test species to ensure reliable, relevant, reproducible, defensible and ecologically significant results. The selection of a suitable test species can be based on several criteria: • the species should be widely available • they should be easily maintained under laboratory conditions and provide sufficient numbers of an appropriate size and age • the genetics, genetic composition and history of the organisms should be known • they should the most sensitive species in the environment. • should be recreationally, ecologically and commercially important • organisms should be in good physiological condition • it should be indigenous or representative of the eco-region being studies