Putting the eco in ecotoxicology.

Testing of pesticides and often other persistent chemicals increasingly involves aquatic mesocosms. Since our intention is to protect natural systems, predictions of their response based on surrogate systems are desirable. Toxicity tests at a variety of levels of biological organization are now available, ranging from single-species laboratory tests to those carried out in field enclosures of portions of natural systems. Validation is essential to determine accuracy of the predictions that will almost certainly not be identical for the wide variety of testing systems now available. Some important scientific considerations in the development of protocols are discussed.